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Order Artiodactyla/Clade Cetartiodactyla
Family Diacodexeidae
Family Amphimerycidae
Family Robiacinidae
Family Cainotheriidae
Suborder Tylopoda
Family Anoplotheriidae?
Family Merycoidodontidae
Family Agriochoeridae
Family Camelidae: camels, llamas, alpacas, vicuñas, and guanacos (7 extant and 13 extinct species)
Family Oromerycidae
Family Xiphodontidae?
Family Protoceratidae?
Clade Artiofabula
Suborder Suina
Family Suidae: pigs (19 species)
Family Tayassuidae: peccaries (4 species)
Family Sanitheriidae
Family Doliochoeridae
Clade Cetruminantia
Clade Cetancodontamorpha
Genus Andrewsarchus?
Family Entelodontidae
Suborder Whippomorpha
Family Raoellidae
Superfamily Dichobunoidea – paraphyletic to Cetacea and Raoellidae
Family Dichobunidae
Family Helohyidae
Family Choeropotamidae
Family Cebochoeridae (Family contains Cebochoerus)
Family Mixtotheriidae
Infraorder Ancodonta
Family Anthracotheriidae – paraphyletic to Hippopotamidae
Family Hippopotamidae: hippos (two species)
Infraorder Cetacea: whales (about 90 species)
Parvorder Archaeoceti
Family Pakicetidae
Family Ambulocetidae
Family Remingtonocetidae
Family Basilosauridae
Clade Neoceti
Parvorder Mysticeti: baleen whales
Superfamily Balaenoidea: right whales
Family Balaenidae: greater right whales (four species)
Family Cetotheriidae: pygmy right whale (one species)
Superfamily Balaenopteroidea: large baleen whales
Family Balaenopteridae: slender-back rorquals and humpback whale (eight species)
Family Eschrichtiidae: gray whale (one species)
Parvorder Odontoceti: toothed whales
Superfamily Delphinoidea: oceanic dolphins, porpoises, and others
Family Delphinidae: oceanic true dolphins (38 species)
Family Monodontidae: Arctic whales; narwhal and beluga (two species)
Family Phocoenidae: porpoises (six species)
Superfamily Physeteroidea: sperm whales | Artiodactyl | Wikipedia | 502 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Family Kogiidae: lesser sperm whales (two species)
Family Physeteridae: sperm whale (one species)
Superfamily Platanistoidea: river dolphins
Family Iniidae: South American river dolphins (two species)
Family Lipotidae: Chinese river dolphin (one species, possibly extinct)
Family Platanistidae: South Asian river dolphin (one species)
Family Pontoporiidae: La Plata dolphin (one species)
Superfamily Ziphioidea
Family Ziphiidae: beaked whales (22 species)
Total-group Ruminantia
Suborder Ruminantia
Infraorder Tragulina
Family Leptomerycidae
Family Hypertragulidae
Family Praetragulidae
Family Gelocidae
Family Bachitheriidae
Family Tragulidae: chevrotains (ten species)
Family Archaeomerycidae
Family Lophiomerycidae
Infraorder Pecora
Family Palaeomerycidae
Family Dromomerycidae
Family Antilocapridae: pronghorn (one species)
Family Climacoceratidae
Family Giraffidae: okapi and four species of giraffe (five species total)
Family Hoplitomerycidae
Family Cervidae: deer (49 species)
Family Moschidae: musk deer (7 species)
Family Bovidae: cattle, buffaloes, goats, sheep, antelopes, caprines, and bison (135 species) | Artiodactyl | Wikipedia | 299 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Research history
In the 1990s, biological systematics used not only morphology and fossils to classify organisms, but also molecular biology. Molecular biology involves sequencing an organism's DNA and RNA and comparing the sequence with that of other living beings—the more similar they are, the more closely they are related. Comparison of even-toed ungulate and cetaceans genetic material has shown that the closest living relatives of whales and hippopotamuses is the paraphyletic group Artiodactyla.
Dan Graur and Desmond Higgins were among the first to come to this conclusion, and included a paper published in 1994. However, they did not recognize hippopotamuses and classified the ruminants as the sister group of cetaceans. Subsequent studies established the close relationship between hippopotamuses and cetaceans; these studies were based on casein genes, SINEs, fibrinogen sequences, cytochrome and rRNA sequences, IRBP (and vWF) gene sequences, adrenergic receptors, and apolipoproteins.
In 2001, the fossil limbs of a Pakicetus (amphibioid cetacean the size of a wolf) and Ichthyolestes (an early whale the size of a fox) were found in Pakistan. They were both archaeocetes ("ancient whales") from about 48 million years ago (in the Eocene). These findings showed that archaeocetes were more terrestrial than previously thought, and that the special construction of the talus (ankle bone) with a double-rolled joint surface, previously thought to be unique to even-toed ungulates, were also in early cetaceans. The mesonychians, another type of ungulate, did not show this special construction of the talus, and thus was concluded to not have the same ancestors as cetaceans. | Artiodactyl | Wikipedia | 397 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
The oldest cetaceans date back to the early Eocene (53 million years ago), whereas the oldest known hippopotamus dates back only to the Miocene (15 million years ago). The hippopotamids are descended from the anthracotheres, a family of semiaquatic and terrestrial artiodactyls that appeared in the late Eocene, and are thought to have resembled small- or narrow-headed hippos. Research is therefore focused on anthracotheres (family Anthracotheriidae); one dating from the Eocene to Miocene was declared to be "hippo-like" upon discovery in the 19th century. A study from 2005 showed that the anthracotheres and hippopotamuses had very similar skulls, but differed in the adaptations of their teeth. It was nevertheless believed that cetaceans and anthracothereres descended from a common ancestor, and that hippopotamuses developed from anthracotheres. A study published in 2015 confirmed this, but also revealed that hippopotamuses were derived from older anthracotherians. The newly introduced genus Epirigenys from Eastern Africa is thus the sister group of hippos.
Historical classification of Artiodactyla
Linnaeus postulated a close relationship between camels and ruminants as early as the mid-1700s. Henri de Blainville recognized the similar anatomy of the limbs of pigs and hippos, and British zoologist Richard Owen coined the term "even-toed ungulates" and the scientific name "Artiodactyla" in 1848.
Internal morphology (mainly the stomach and the molars) were used for classification. Suines (including pigs) and hippopotamuses have molars with well-developed roots and a simple stomach that digests food. Thus, they were grouped together as non-ruminants (porcine). All other even-toed ungulates have molars with a selenodont construction (crescent-shaped cusps) and have the ability to ruminate, which requires regurgitating food and re-chewing it. Differences in stomach construction indicated that rumination evolved independently between tylopods and ruminants; therefore, tylopods were excluded from Ruminantia.
The taxonomy that was widely accepted by the end of the 20th century was:
Historical classification of Cetacea | Artiodactyl | Wikipedia | 499 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Modern cetaceans are highly adapted sea creatures which, morphologically, have little in common with land mammals; they are similar to other marine mammals, such as seals and sea cows, due to convergent evolution. However, they evolved from originally terrestrial mammals. The most likely ancestors were long thought to be mesonychians—large, carnivorous animals from the early Cenozoic (Paleocene and Eocene), which had hooves instead of claws on their feet. Their molars were adapted to a carnivorous diet, resembling the teeth in modern toothed whales, and, unlike other mammals, had a uniform construction.
The suspected relations can be shown as follows:
Inner systematics
Molecular findings and morphological indications suggest that artiodactyls, as traditionally defined, are paraphyletic with respect to cetaceans. Cetaceans are deeply nested within the former; the two groups together form a monophyletic taxon, for which the name Cetartiodactyla is sometimes used. Modern nomenclature divides Artiodactyla (or Cetartiodactyla) in four subordinate taxa: camelids (Tylopoda), pigs and peccaries (Suina), ruminants (Ruminantia), and hippos plus cetaceans (Whippomorpha).
The presumed lineages within Artiodactyla can be represented in the following cladogram: | Artiodactyl | Wikipedia | 297 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
The four summarized Artiodactyla taxa are divided into ten extant families:
The camelids (Tylopoda) comprise only one family, Camelidae. It is a species-poor artiodactyl suborder of North American origin that is well adapted to extreme habitats—the dromedary and Bactrian camels in the Old World deserts and the guanacos, llamas, vicuñas, and alpacas in South American high mountain regions.
The pig-like creatures (Suina) are made up of two families:
The pigs (Suidae) are limited to the Old World. These include the wild boar and the domesticated form, the domestic pig.
The peccaries (Tayassuidae) are named after glands on their belly and are indigenous to Central and South America.
The ruminants (Ruminantia) consist of six families:
The mouse deer (Tragulidae) are the smallest and most primitive even-toed-ruminants; they inhabit forests of Africa and Asia.
The giraffe-like creatures (Giraffidae) are composed of two species: the giraffe and the okapi.
The musk deer (Moschidae) is indigenous to East Asia.
The antilocaprids (Antilocapridae) of North America comprise only one extant species: the pronghorn.
The deer (Cervidae) are made up of about 45 species, which are characterized by a pair of antlers (generally only in males). They are spread across Europe, Asia, and the Americas. This group includes, among other species, the red deer, moose, elk (wapiti), and reindeer (caribou).
The bovids (Bovidae) are the most species-rich. Among them are cattle, sheep, caprines, and antelopes, and more.
The whippomorphs include hippos and cetaceans:
The hippos (Hippopotamidae) comprise two groups, the common hippo and the pygmy hippo.
The cetaceans comprise 72 species and two parvorders: toothed whales (Odontoceti) and baleen whales (Mysticeti) | Artiodactyl | Wikipedia | 471 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Although deer, musk deer, and pronghorns have traditionally been summarized as cervids (Cervioidea), molecular studies provide different—and inconsistent—results, so the question of phylogenetic systematics of infraorder Pecora (the horned ruminants) for the time being, cannot be answered.
Anatomy
Artiodactyls are generally quadrupeds. Two major body types are known: suinids and hippopotamuses are characterized by a stocky body, short legs, and a large head; camels and ruminants, though, have a more slender build and lanky legs. Size varies considerably; the smallest member, the mouse deer, often reaches a body length of only and a weight of . The largest member, the hippopotamus, can grow up to in length and weigh , and the giraffe can grow to be tall and in body length. All even-toed ungulates display some form of sexual dimorphism: the males are consistently larger and heavier than the females. In deer, only the males boast antlers, and the horns of bovines are usually small or not present in females. Male Indian antelopes have a much darker coat than females.
Almost all even-toed ungulates have fur, with the exception being the nearly hairless hippopotamus. Fur varies in length and coloration depending on the habitat. Species in cooler regions can shed their coat. Camouflaged coats come in colors of yellow, gray, brown, or black tones.
Limbs
Even-toed ungulates bear their name because they have an even number of toes (two or four)—in some peccaries, the hind legs have a reduction in the number of toes to three. The central axis of the leg is between the third and fourth toe. The first toe is missing in modern artiodactyls, and can only be found in now-extinct genera. The second and fifth toes are adapted differently between species: | Artiodactyl | Wikipedia | 419 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
When camels have only two toes present, the claws are transformed into nails (while both are made of keratin, claws are curved and pointed while nails are flat and dull). These claws consist of three parts: the plate (top and sides), the sole (bottom), and the bale (rear). In general, the claws of the forelegs are wider and blunter than those of the hind legs, and they are farther apart. Aside from camels, all even-toed ungulates put just the tip of the foremost phalanx on the ground.
In even-toed ungulates, the bones of the stylopodium (upper arm or thigh bone) and zygopodiums (tibia and fibula) are usually elongated. The muscles of the limbs are predominantly localized, which ensures that artiodactyls often have very slender legs. A clavicle is never present, and the scapula is very agile and swings back and forth for added mobility when running. The special construction of the legs causes the legs to be unable to rotate, which allows for greater stability when running at high speeds. In addition, many smaller artiodactyls have a very flexible body, contributing to their speed by increasing their stride length.
Head
Many even-toed ungulates have a relatively large head. The skull is elongated and rather narrow; the frontal bone is enlarged near the back and displaces the parietal bone, which forms only part of the side of the cranium (especially in ruminants).
Horns and antlers
Four families of even-toed ungulates have cranial appendages. These Pecora (with the exception of the musk deer), have one of four types of cranial appendages: true horns, antlers, ossicones, or pronghorns. | Artiodactyl | Wikipedia | 395 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
True horns have a bone core that is covered in a permanent sheath of keratin, and are found only in the bovids. Antlers are bony structures that are shed and replaced each year; they are found in deer (members of the family Cervidae). They grow from a permanent outgrowth of the frontal bone called the pedicle and can be branched, as in the white-tailed deer (Odocoileus virginianus), or palmate, as in the moose (Alces alces). Ossicones are permanent bone structures that fuse to the frontal or parietal bones during an animal's life and are found only in the Giraffidae. Pronghorns, while similar to horns in that they have keratinous sheaths covering permanent bone cores, are deciduous.
All these cranial appendages can serve for posturing, battling for mating privilege, and for defense. In almost all cases, they are sexually dimorphic, and are often found only on the males. One exception is the species Rangifer tarandus, known as reindeer in Europe or caribou in North America, where both sexes can grow antlers yearly, though the females' antlers are typically smaller and not always present.
Teeth
There are two trends in terms of teeth within Artiodactyla. The Suina and hippopotamuses have a relatively large number of teeth (with some pigs having 44); their dentition is more adapted to a squeezing mastication, which is characteristic of omnivores. Camels and ruminants have fewer teeth; there is often a yawning diastema, a designated gap in the teeth where the molars are aligned for crushing plant matter.
The incisors are often reduced in ruminants, and are completely absent in the upper jaw. The canines are enlarged and tusk-like in the Suina, and are used for digging in the ground and for defense. In ruminants, the males' upper canines are enlarged and used as a weapon in certain species (mouse deer, musk deer, water deer); species with frontal weapons are usually missing the upper canines. The lower canines of ruminants resemble the incisors, so that these animals have eight uniform teeth in the frontal part of the lower jaw. | Artiodactyl | Wikipedia | 484 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
The molars of porcine have only a few bumps. In contrast, camels and ruminants have bumps that are crescent-shaped cusps (selenodont).
Senses
Artiodactyls have a well-developed sense of smell and sense of hearing. Unlike many other mammals, they have a poor sense of sight—moving objects are much easier to see than stationary ones. Similar to many other prey animals, their eyes are on the sides of the head, giving them an almost panoramic view.
Digestive system
The ruminants (Ruminantia) ruminate their food—they regurgitate and re-chew it. Ruminants' mouths often have additional salivary glands, and the oral mucosa is often heavily calloused to avoid injury from hard plant parts and to allow easier transport of roughly chewed food. Their stomachs are divided into three to four sections: the rumen, the reticulum, the omasum, and the abomasum. After the food is ingested, it is mixed with saliva in the rumen and reticulum and separates into layers of solid versus liquid material. The solids lump together to form a bolus (also known as the cud); this is regurgitated by reticular contractions while the glottis is closed. When the bolus enters the mouth, the fluid is squeezed out with the tongue and re-swallowed. The bolus is chewed slowly to completely mix it with saliva and to break it down. Ingested food passes to the "fermentation chamber" (rumen and reticulum), where it is kept in continual motion by rhythmic contractions. Cellulytic microbes (bacteria, protozoa, and fungi) produce cellulase, which is needed to break down the cellulose found in plant material. This form of digestion has two advantages: plants that are indigestible to other species can be digested and used, and the duration of the actual food consumption shortened; the animal spends only a short time out in the open with its head to the ground—rumination can take place later, in a sheltered area. | Artiodactyl | Wikipedia | 448 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Tylopoda (camels, llamas, and alpacas) and chevrotains have three-chambered stomachs, while the rest of Ruminantia have four-chambered stomachs. The handicap of a heavy digestive system has increased selective pressure towards limbs that allow the animal to quickly escape predators. Most species within Suina have a simple two-chambered stomach that allows for an omnivorous diet. The babirusa, however, is a herbivore, and has extra maxillary teeth to allow for proper mastication of plant material. Most of the fermentation occurs with the help of cellulolytic microorganisms within the caecum of the large intestine. Peccaries have a complex stomach that contains four compartments. Their fore stomach has fermentation carried out by microbes and has high levels of volatile fatty acid; it has been proposed that their complex fore-stomach is a means to slow digestive passage and increase digestive efficiency. Hippopotamuses have three-chambered stomachs and do not ruminate. They consume around of grass and other plant matter each night. They may cover distances up to to obtain food, which they digest with the help of microbes that produce cellulase. Their closest living relatives, the whales, are obligate carnivores.
Unlike other even-toed ungulates, pigs have a simple sack-shaped stomach. Some artiodactyls, such as white-tailed deer, lack a gall bladder.
Genitourinary system
The penises of even-toed ungulates have an S-shape at rest and lie in a pocket under the skin on the belly. The corpora cavernosa are only slightly developed; and an erection mainly causes this curvature to extend, which leads to an extension, but not a thickening, of the penis. Cetaceans have similar penises. In some even-toed ungulates, the penis contains a structure called the urethral process or penile vermiform appendix.
The testicles are located in the scrotum and thus outside the abdominal cavity. The ovaries of many females descend—as the testicles descend of many male mammals—and are close to the pelvic inlet at the level of the fourth lumbar vertebra. The uterus has two horns (uterus bicornis).
Other | Artiodactyl | Wikipedia | 500 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
The number of mammary glands is variable and correlates, as in all mammals, with litter size. Pigs, which have the largest litter size of all even-toed ungulates, have two rows of teats lined from the armpit to the groin area. In most cases, however, even-toed ungulates have only one or two pairs of teats. In some species these form an udder in the groin region.
Secretory glands in the skin are present in virtually all species and can be located in different places, such as in the eyes, behind the horns, the neck, or back, on the feet, or in the anal region.
Artiodactyls have a carotid rete heat exchange that enables them, unlike perissodactyls which lack one, to regulate their brain temperature independently of their bodies. It has been argued that its presence explains the greater success of artiodactyls compared to perissodactyls in being able to adapt to diverse environments from the Arctic Circle to deserts and tropical savannahs.
Lifestyle
Distribution and habitat
Artiodactyls are native to almost all parts of the world, with the exception of Oceania and Antarctica. Humans have introduced different artiodactyls worldwide as hunting animals. Artiodactyls inhabit almost every habitat, from tropical rainforests and steppes to deserts and high mountain regions. The greatest biodiversity prevails in open habitats such as grasslands and open forests.
Social behavior
The social behavior of even-toed ungulates varies from species to species. Generally, there is a tendency to merge into larger groups, but some live alone or in pairs. Species living in groups often have a hierarchy, both among males and females. Some species also live in harem groups, with one male, several females, and their common offspring. In other species, the females and juveniles stay together, while males are solitary or live in bachelor groups and seek out females only during mating season.
Many artiodactyls are territorial and mark their territory, for example, with glandular secretions or urine. In addition to year-round sedentary species, there are animals that migrate seasonally.
There are diurnal, crepuscular, and nocturnal artiodactyls. Some species' pattern of wakefulness varies with season or habitat.
Reproduction and life expectancy | Artiodactyl | Wikipedia | 494 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Generally, even-toed ungulates tend to have long gestation periods, smaller litter sizes, and more highly developed newborns. As with many other mammals, species in temperate or polar regions have a fixed mating season, while those in tropical areas breed year-round. They carry out polygynous mating behavior, meaning a male mates with several females and suppresses all competition.
The length of the gestation period varies from four to five months for porcine, deer, and musk deer; six to ten months for hippos, deer, and bovines; ten to thirteen months with camels; and fourteen to fifteen months with giraffes. Most deliver one or two babies, but some pigs can deliver up to ten.
The newborns are precocial (born relatively mature) and come with open eyes and are hairy (with the exception of the hairless hippos). Juvenile deer and pigs have striped or spotted coats; the pattern disappears as they grow older. The juveniles of some species spend their first weeks with their mother in a safe location, where others may be running and following the herd within a few hours or days.
Life expectancy is typically twenty to thirty years; as in many mammals, smaller species often have a shorter lifespan than larger species. The artiodactyls with the longest lifespans are the hippos, cows, and camels, which can live 40 to 50 years.
Predators and parasites
Artiodactyls have different natural predators depending on their size and habitat. There are several carnivores that prey on them, including large cats (e.g., lions) and bears. Other predators are crocodiles, wolves and dogs, large raptors, and for small species and young animals, large snakes. For cetaceans, possible predators include sharks, polar bears, and other cetaceans; in the latter is the orca, the top predator of the oceans.
Parasites include nematodes, botflies, fleas, lice, or flukes, but they have debilitating effects only when the infestation is severe.
Interactions with humans
Domestication | Artiodactyl | Wikipedia | 442 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Artiodactyls have been hunted by primitive humans for various reasons: for meat or fur, as well as to use their bones and teeth as weapons or tools. Their domestication began around 8000 BCE. To date, humans have domesticated goats, sheep, cattle, camels, llamas, alpacas, and pigs. Initially, livestock was used primarily for food, but they began being used for work activities around 3000 BCE. Clear evidence exists of antelope being used for food 2 million years ago in the Olduvai Gorge, part of the Great Rift Valley. Cro-Magnons relied heavily on reindeer for food, skins, tools, and weapons; with dropping temperatures and increased reindeer numbers at the end of the Pleistocene, they became the prey of choice. Reindeer remains accounted for 94% of bones and teeth found in a cave above the river Céou that was inhabited around 12,500 years ago. In general, most even-toed ungulates can be consumed as a kosher meat, with the principal exception of Suina (pigs, etc.) and hippopotamids, which are even-toed but do not chew the cud, and of Cetacea, which, for the purpose of rabbinic law, are considered to be scaleless fish, and thus not kosher.
Today, artiodactyls are kept primarily for their meat, milk, and wool, fur, or hide for clothing. Domestic cattle, the water buffalo, the yak, and camels are used for work, as rides, or as pack animals.
Threats
The endangerment level of each even-toed ungulate is different. Some species are synanthropic (such as the wild boar) and have spread into areas that they are not indigenous to, either having been brought in as farm animals or having run away as people's pets. Some artiodactyls also benefit from the fact that their predators (e.g., the Tasmanian tiger) were severely decimated by ranchers, who saw them as competition. | Artiodactyl | Wikipedia | 432 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
Conversely, many artiodactyls have declined significantly in numbers, and some have even gone extinct, largely due to over-hunting, and, more recently, habitat destruction. Extinct species include several gazelles, the aurochs, the Malagasy hippopotamus, the bluebuck, and Schomburgk's deer. Two species, the scimitar-horned oryx and Père David's deer, are extinct in the wild. 14 species are considered critically endangered, including the addax, the kouprey, the wild Bactrian camel, Przewalski's gazelle, the saiga, and the pygmy hog. 24 species are considered endangered. | Artiodactyl | Wikipedia | 145 | 46764 | https://en.wikipedia.org/wiki/Artiodactyl | Biology and health sciences | Artiodactyla | null |
A fixed-wing aircraft is a heavier-than-air aircraft, such as an airplane, which is capable of flight using aerodynamic lift. Fixed-wing aircraft are distinct from rotary-wing aircraft (in which a rotor mounted on a spinning shaft generates lift), and ornithopters (in which the wings oscillate to generate lift). The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders, variable-sweep wing aircraft, and airplanes that use wing morphing are all classified as fixed wing.
Gliding fixed-wing aircraft, including free-flying gliders and tethered kites, can use moving air to gain altitude. Powered fixed-wing aircraft (airplanes) that gain forward thrust from an engine include powered paragliders, powered hang gliders and ground effect vehicles. Most fixed-wing aircraft are operated by a pilot, but some are unmanned and controlled either remotely or autonomously.
History
Kites
Kites were used approximately 2,800 years ago in China, where kite building materials were available. Leaf kites may have been flown earlier in what is now Sulawesi, based on their interpretation of cave paintings on nearby Muna Island. By at least 549 AD paper kites were flying, as recorded that year, a paper kite was used as a message for a rescue mission. Ancient and medieval Chinese sources report kites used for measuring distances, testing the wind, lifting men, signaling, and communication for military operations.
Kite stories were brought to Europe by Marco Polo towards the end of the 13th century, and kites were brought back by sailors from Japan and Malaysia in the 16th and 17th centuries. Although initially regarded as curiosities, by the 18th and 19th centuries kites were used for scientific research.
Gliders and powered devices
Around 400 BC in Greece, Archytas was reputed to have designed and built the first self-propelled flying device, shaped like a bird and propelled by a jet of what was probably steam, said to have flown some . This machine may have been suspended during its flight.
One of the earliest attempts with gliders was by 11th-century monk Eilmer of Malmesbury, which failed. A 17th-century account states that 9th-century poet Abbas Ibn Firnas made a similar attempt, though no earlier sources record this event. | Fixed-wing aircraft | Wikipedia | 473 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
In 1799, Sir George Cayley laid out the concept of the modern airplane as a fixed-wing machine with systems for lift, propulsion, and control. Cayley was building and flying models of fixed-wing aircraft as early as 1803, and built a successful passenger-carrying glider in 1853. In 1856, Frenchman Jean-Marie Le Bris made the first powered flight, had his glider L'Albatros artificiel towed by a horse along a beach. In 1884, American John J. Montgomery made controlled flights in a glider as a part of a series of gliders he built between 1883 and 1886. Other aviators who made similar flights at that time were Otto Lilienthal, Percy Pilcher, and protégés of Octave Chanute.
In the 1890s, Lawrence Hargrave conducted research on wing structures and developed a box kite that lifted the weight of a man. His designs were widely adopted. He also developed a type of rotary aircraft engine, but did not create a powered fixed-wing aircraft.
Powered flight
Sir Hiram Maxim built a craft that weighed 3.5 tons, with a 110-foot (34-meter) wingspan powered by two 360-horsepower (270-kW) steam engines driving two propellers. In 1894, his machine was tested with overhead rails to prevent it from rising. The test showed that it had enough lift to take off. The craft was uncontrollable, and Maxim abandoned work on it.
The Wright brothers' flights in 1903 with their Flyer I are recognized by the Fédération Aéronautique Internationale (FAI), the standard setting and record-keeping body for aeronautics, as "the first sustained and controlled heavier-than-air powered flight". By 1905, the Wright Flyer III was capable of fully controllable, stable flight for substantial periods.
In 1906, Brazilian inventor Alberto Santos Dumont designed, built and piloted an aircraft that set the first world record recognized by the Aéro-Club de France by flying the 14 bis in less than 22 seconds. The flight was certified by the FAI.
The Bleriot VIII design of 1908 was an early aircraft design that had the modern monoplane tractor configuration. It had movable tail surfaces controlling both yaw and pitch, a form of roll control supplied either by wing warping or by ailerons and controlled by its pilot with a joystick and rudder bar. It was an important predecessor of his later Bleriot XI Channel-crossing aircraft of the summer of 1909.
World War I | Fixed-wing aircraft | Wikipedia | 504 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
World War I served initiated the use of aircraft as weapons and observation platforms. The earliest known aerial victory with a synchronized machine gun-armed fighter aircraft occurred in 1915, flown by German Luftstreitkräfte Lieutenant Kurt Wintgens. Fighter aces appeared; the greatest (by number of air victories) was Manfred von Richthofen.
Alcock and Brown crossed the Atlantic non-stop for the first time in 1919. The first commercial flights traveled between the United States and Canada in 1919.
Interwar aviation; the "Golden Age"
The so-called Golden Age of Aviation occurred between the two World Wars, during which updated interpretations of earlier breakthroughs. Innovations include Hugo Junkers' all-metal air frames in 1915 leading to multi-engine aircraft of up to 60+ meter wingspan sizes by the early 1930s, adoption of the mostly air-cooled radial engine as a practical aircraft power plant alongside V-12 liquid-cooled aviation engines, and longer and longer flights – as with a Vickers Vimy in 1919, followed months later by the U.S. Navy's NC-4 transatlantic flight; culminating in May 1927 with Charles Lindbergh's solo trans-Atlantic flight in the Spirit of St. Louis spurring ever-longer flight attempts.
World War II
Airplanes had a presence in the major battles of World War II. They were an essential component of military strategies, such as the German Blitzkrieg or the American and Japanese aircraft carrier campaigns of the Pacific.
Military gliders were developed and used in several campaigns, but were limited by the high casualty rate encountered. The Focke-Achgelis Fa 330 Bachstelze (Wagtail) rotor kite of 1942 was notable for its use by German U-boats.
Before and during the war, British and German designers worked on jet engines. The first jet aircraft to fly, in 1939, was the German Heinkel He 178. In 1943, the first operational jet fighter, the Messerschmitt Me 262, went into service with the German Luftwaffe. Later in the war the British Gloster Meteor entered service, but never saw action – top air speeds for that era went as high as , with the early July 1944 unofficial record flight of the German Me 163B V18 rocket fighter prototype.
Postwar
In October 1947, the Bell X-1 was the first aircraft to exceed the speed of sound, flown by Chuck Yeager. | Fixed-wing aircraft | Wikipedia | 491 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
In 1948–49, aircraft transported supplies during the Berlin Blockade. New aircraft types, such as the B-52, were produced during the Cold War.
The first jet airliner, the de Havilland Comet, was introduced in 1952, followed by the Soviet Tupolev Tu-104 in 1956. The Boeing 707, the first widely successful commercial jet, was in commercial service for more than 50 years, from 1958 to 2010. The Boeing 747 was the world's largest passenger aircraft from 1970 until it was surpassed by the Airbus A380 in 2005. The most successful aircraft is the Douglas DC-3 and its military version, the C-47, a medium sized twin engine passenger or transport aircraft that has been in service since 1936 and is still used throughout the world. Some of the hundreds of versions found other purposes, like the AC-47, a Vietnam War era gunship, which is still used in the Colombian Air Force.
Types
Airplane/aeroplane
An airplane (aeroplane or plane) is a powered fixed-wing aircraft propelled by thrust from a jet engine or propeller. Planes come in many sizes, shapes, and wing configurations. Uses include recreation, transportation of goods and people, military, and research.
Seaplane
A seaplane (hydroplane) is capable of taking off and landing (alighting) on water. Seaplanes that can also operate from dry land are a subclass called amphibian aircraft. Seaplanes and amphibians divide into two categories: float planes and flying boats.
A float plane is similar to a land-based airplane. The fuselage is not specialized. The wheels are replaced/enveloped by floats, allowing the craft to make remain afloat for water landings.
A flying boat is a seaplane with a watertight hull for the lower (ventral) areas of its fuselage. The fuselage lands and then rests directly on the water's surface, held afloat by the hull. It does not need additional floats for buoyancy, although small underwing floats or fuselage-mounted sponsons may be used to stabilize it. Large seaplanes are usually flying boats, embodying most classic amphibian aircraft designs.
Powered gliders | Fixed-wing aircraft | Wikipedia | 442 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Many forms of glider may include a small power plant. These include:
Motor glider – a conventional glider or sailplane with an auxiliary power plant that may be used when in flight to increase performance.
Powered hang glider – a hang glider with a power plant added.
Powered parachute – a paraglider type of parachute with an integrated air frame, seat, undercarriage and power plant hung beneath.
Powered paraglider or paramotor – a paraglider with a power plant suspended behind the pilot.
Ground effect vehicle
A ground effect vehicle (GEV) flies close to the terrain, making use of the ground effect – the interaction between the wings and the surface. Some GEVs are able to fly higher out of ground effect (OGE) when required – these are classed as powered fixed-wing aircraft.
Glider
A glider is a heavier-than-air craft whose free flight does not require an engine. A sailplane is a fixed-wing glider designed for soaring – gaining height using updrafts of air and to fly for long periods.
Gliders are mainly used for recreation but have found use for purposes such as aerodynamics research, warfare and spacecraft recovery.
Motor gliders are equipped with a limited propulsion system for takeoff, or to extend flight duration.
As is the case with planes, gliders come in diverse forms with varied wings, aerodynamic efficiency, pilot location, and controls.
Large gliders are most commonly born aloft by a tow-plane or by a winch. Military gliders have been used in combat to deliver troops and equipment, while specialized gliders have been used in atmospheric and aerodynamic research. Rocket-powered aircraft and spaceplanes have made unpowered landings similar to a glider.
Gliders and sailplanes that are used for the sport of gliding have high aerodynamic efficiency. The highest lift-to-drag ratio is 70:1, though 50:1 is common. After take-off, further altitude can be gained through the skillful exploitation of rising air. Flights of thousands of kilometers at average speeds over 200 km/h have been achieved.
One small-scale example of a glider is the paper airplane. An ordinary sheet of paper can be folded into an aerodynamic shape fairly easily; its low mass relative to its surface area reduces the required lift for flight, allowing it to glide some distance. | Fixed-wing aircraft | Wikipedia | 468 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Gliders and sailplanes share many design elements and aerodynamic principles with powered aircraft. For example, the Horten H.IV was a tailless flying wing glider, and the delta-winged Space Shuttle orbiter glided during its descent phase. Many gliders adopt similar control surfaces and instruments as airplanes.
Types
The main application of modern glider aircraft is sport and recreation.
Sailplane
Gliders were developed in the 1920s for recreational purposes. As pilots began to understand how to use rising air, sailplane gliders were developed with a high lift-to-drag ratio. These allowed the craft to glide to the next source of "lift", increasing their range. This gave rise to the popular sport of gliding.
Early gliders were built mainly of wood and metal, later replaced by composite materials incorporating glass, carbon or aramid fibers. To minimize drag, these types have a streamlined fuselage and long narrow wings incorporating a high aspect ratio. Single-seat and two-seat gliders are available.
Initially, training was done by short "hops" in primary gliders, which have no cockpit and minimal instruments. Since shortly after World War II, training is done in two-seat dual control gliders, but high-performance two-seaters can make long flights. Originally skids were used for landing, later replaced by wheels, often retractable. Gliders known as motor gliders are designed for unpowered flight, but can deploy piston, rotary, jet or electric engines. Gliders are classified by the FAI for competitions into glider competition classes mainly on the basis of wingspan and flaps.
A class of ultralight sailplanes, including some known as microlift gliders and some known as airchairs, has been defined by the FAI based on weight. They are light enough to be transported easily, and can be flown without licensing in some countries. Ultralight gliders have performance similar to hang gliders, but offer some crash safety as the pilot can strap into an upright seat within a deform-able structure. Landing is usually on one or two wheels which distinguishes these craft from hang gliders. Most are built by individual designers and hobbyists.
Military gliders | Fixed-wing aircraft | Wikipedia | 441 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Military gliders were used during World War II for carrying troops (glider infantry) and heavy equipment to combat zones. The gliders were towed into the air and most of the way to their target by transport planes, e.g. C-47 Dakota, or by one-time bombers that had been relegated to secondary activities, e.g. Short Stirling. The advantage over paratroopers were that heavy equipment could be landed and that troops were quickly assembled rather than dispersed over a parachute drop zone. The gliders were treated as disposable, constructed from inexpensive materials such as wood, though a few were re-used. By the time of the Korean War, transport aircraft had become larger and more efficient so that even light tanks could be dropped by parachute, obsoleting gliders.
Research gliders
Even after the development of powered aircraft, gliders continued to be used for aviation research. The NASA Paresev Rogallo flexible wing was developed to investigate alternative methods of recovering spacecraft. Although this application was abandoned, publicity inspired hobbyists to adapt the flexible-wing airfoil for hang gliders.
Initial research into many types of fixed-wing craft, including flying wings and lifting bodies was also carried out using unpowered prototypes.
Hang glider
A hang glider is a glider aircraft in which the pilot is suspended in a harness suspended from the air frame, and exercises control by shifting body weight in opposition to a control frame. Hang gliders are typically made of an aluminum alloy or composite-framed fabric wing. Pilots can soar for hours, gain thousands of meters of altitude in thermal updrafts, perform aerobatics, and glide cross-country for hundreds of kilometers.
Paraglider
A paraglider is a lightweight, free-flying, foot-launched glider with no rigid body. The pilot is suspended in a harness below a hollow fabric wing whose shape is formed by its suspension lines. Air entering vents in the front of the wing and the aerodynamic forces of the air flowing over the outside power the craft. Paragliding is most often a recreational activity.
Unmanned gliders
A paper plane is a toy aircraft (usually a glider) made out of paper or paperboard.
Model glider aircraft are models of aircraft using lightweight materials such as polystyrene and balsa wood. Designs range from simple glider aircraft to accurate scale models, some of which can be very large. | Fixed-wing aircraft | Wikipedia | 484 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Glide bombs are bombs with aerodynamic surfaces to allow a gliding flight path rather than a ballistic one. This enables stand-off aircraft to attack a target from a distance.
Kite
A kite is a tethered aircraft held aloft by wind that blows over its wing(s). High pressure below the wing deflects the airflow downwards. This deflection generates horizontal drag in the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of the tether.
Kites are mostly flown for recreational purposes, but have many other uses. Early pioneers such as the Wright Brothers and J.W. Dunne sometimes flew an aircraft as a kite in order to confirm its flight characteristics, before adding an engine and flight controls.
Applications
Military
Kites have been used for signaling, for delivery of munitions, and for observation, by lifting an observer above the field of battle, and by using kite aerial photography.
Science and meteorology
Kites have been used for scientific purposes, such as Benjamin Franklin's famous experiment proving that lightning is electricity. Kites were the precursors to the traditional aircraft, and were instrumental in the development of early flying craft. Alexander Graham Bell experimented with large man-lifting kites, as did the Wright brothers and Lawrence Hargrave. Kites had a historical role in lifting scientific instruments to measure atmospheric conditions for weather forecasting.
Radio aerials and light beacons
Kites can be used to carry radio antennas. This method was used for the reception station of the first transatlantic transmission by Marconi. Captive balloons may be more convenient for such experiments, because kite-carried antennas require strong wind, which may be not always available with heavy equipment and a ground conductor.
Kites can be used to carry light sources such as light sticks or battery-powered lights.
Kite traction
Kites can be used to pull people and vehicles downwind. Efficient foil-type kites such as power kites can also be used to sail upwind under the same principles as used by other sailing craft, provided that lateral forces on the ground or in the water are redirected as with the keels, center boards, wheels and ice blades of traditional sailing craft. In the last two decades, kite sailing sports have become popular, such as kite buggying, kite landboarding, kite boating and kite surfing. Snow kiting is also popular.
Kite sailing opens several possibilities not available in traditional sailing: | Fixed-wing aircraft | Wikipedia | 494 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Wind speeds are greater at higher altitudes
Kites may be maneuvered dynamically, which dramatically increases the available force
Mechanical structures are not needed to withstand bending forces; vehicles/hulls can be light or eliminated.
Power generation
Research and development projects investigate kites for harnessing high altitude wind currents for electricity generation.
Cultural uses
Kite festivals are a popular form of entertainment throughout the world. They include local events, traditional festivals and major international festivals.
Designs
Bermuda kite
Bowed kite, e.g. Rokkaku
Cellular or box kite
Chapi-chapi
Delta kite
Foil, parafoil or bow kite
Malay kite see also wau bulan
Tetrahedral kite
Types
Expanded polystyrene kite
Fighter kite
Indoor kite
Inflatable single-line kite
Kytoon
Man-lifting kite
Rogallo parawing kite
Stunt (sport) kite
Water kite
Characteristics
Air frame
The structural element of a fixed-wing aircraft is the air frame. It varies according to the aircraft's type, purpose, and technology. Early airframes were made of wood with fabric wing surfaces, When engines became available for powered flight, their mounts were made of metal. As speeds increased metal became more common until by the end of World War II, all-metal (and glass) aircraft were common. In modern times, composite materials became more common.
Typical structural elements include:
One or more mostly horizontal wings, often with an airfoil cross-section. The wing deflects air downward as the aircraft moves forward, generating lifting force to support it in flight. The wing also provides lateral stability to stop the aircraft level in steady flight. Other roles are to hold the fuel and mount the engines. | Fixed-wing aircraft | Wikipedia | 336 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
A fuselage, typically a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically slippery. The fuselage joins the other parts of the air frame and contains the payload, and flight systems.
A vertical stabilizer or fin is a rigid surface mounted at the rear of the plane and typically protruding above it. The fin stabilizes the plane's yaw (turn left or right) and mounts the rudder which controls its rotation along that axis.
A horizontal stabilizer, usually mounted at the tail near the vertical stabilizer. The horizontal stabilizer is used to stabilize the plane's pitch (tilt up or down) and mounts the elevators that provide pitch control.
Landing gear, a set of wheels, skids, or floats that support the plane while it is not in flight. On seaplanes, the bottom of the fuselage or floats (pontoons) support it while on the water. On some planes, the landing gear retracts during the flight to reduce drag.
Wings
The wings of a fixed-wing aircraft are static planes extending to either side of the aircraft. When the aircraft travels forwards, air flows over the wings that are shaped to create lift.
Structure
Kites and some lightweight gliders and airplanes have flexible wing surfaces that are stretched across a frame and made rigid by the lift forces exerted by the airflow over them. Larger aircraft have rigid wing surfaces.
Whether flexible or rigid, most wings have a strong frame to give them shape and to transfer lift from the wing surface to the rest of the aircraft. The main structural elements are one or more spars running from root to tip, and ribs running from the leading (front) to the trailing (rear) edge.
Early airplane engines had little power and light weight was critical. Also, early airfoil sections were thin, and could not support a strong frame. Until the 1930s, most wings were so fragile that external bracing struts and wires were added. As engine power increased, wings could be made heavy and strong enough that bracing was unnecessary. Such an unbraced wing is called a cantilever wing.
Configuration
The number and shape of wings vary widely. Some designs blend the wing with the fuselage, while left and right wings separated by the fuselage are more common.
Occasionally more wings have been used, such as the three-winged triplane from World War I. Four-winged quadruplanes and other multiplane designs have had little success. | Fixed-wing aircraft | Wikipedia | 496 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Most planes are monoplanes, with one or two parallel wings. Biplanes and triplanes stack one wing above the other. Tandem wings place one wing behind the other, possibly joined at the tips. When the available engine power increased during the 1920s and 1930s and bracing was no longer needed, the unbraced or cantilever monoplane became the most common form.
The planform is the shape when seen from above/below. To be aerodynamically efficient, wings are straight with a long span, but a short chord (high aspect ratio). To be structurally efficient, and hence lightweight, wingspan must be as small as possible, but offer enough area to provide lift.
To travel at transonic speeds, variable geometry wings change orientation, angling backward to reduce drag from supersonic shock waves. The variable-sweep wing transforms between an efficient straight configuration for takeoff and landing, to a low-drag swept configuration for high-speed flight. Other forms of variable planform have been flown, but none have gone beyond the research stage. The swept wing is a straight wing swept backward or forwards.
The delta wing is a triangular shape that serves various purposes. As a flexible Rogallo wing, it allows a stable shape under aerodynamic forces, and is often used for kites and other ultralight craft. It is supersonic capable, combining high strength with low drag.
Wings are typically hollow, also serving as fuel tanks. They are equipped with flaps, which allow the wing to increase/decrease drag/lift, for take-off and landing, and acting in opposition, to change direction.
Fuselage
The fuselage is typically long and thin, usually with tapered or rounded ends to make its shape aerodynamically smooth. Most fixed-wing aircraft have a single fuselage. Others may have multiple fuselages, or the fuselage may be fitted with booms on either side of the tail to allow the extreme rear of the fuselage to be utilized.
The fuselage typically carries the flight crew, passengers, cargo, and sometimes fuel and engine(s). Gliders typically omit fuel and engines, although some variations such as motor gliders and rocket gliders have them for temporary or optional use. | Fixed-wing aircraft | Wikipedia | 440 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Pilots of manned commercial fixed-wing aircraft control them from inside a cockpit within the fuselage, typically located at the front/top, equipped with controls, windows, and instruments, separated from passengers by a secure door. In small aircraft, the passengers typically sit behind the pilot(s) in the cabin, Occasionally, a passenger may sit beside or in front of the pilot. Larger passenger aircraft have a separate passenger cabin or occasionally cabins that are physically separated from the cockpit.
Aircraft often have two or more pilots, with one in overall command (the "pilot") and one or more "co-pilots". On larger aircraft a navigator is typically also seated in the cockpit as well. Some military or specialized aircraft may have other flight crew members in the cockpit as well.
Wings vs. bodies
Flying wing
A flying wing is a tailless aircraft that has no distinct fuselage, housing the crew, payload, and equipment inside.
The flying wing configuration was studied extensively in the 1930s and 1940s, notably by Jack Northrop and Cheston L. Eshelman in the United States, and Alexander Lippisch and the Horten brothers in Germany. After the war, numerous experimental designs were based on the flying wing concept. General interest continued into the 1950s, but designs did not offer a great advantage in range and presented technical problems. The flying wing is most practical for designs in the slow-to-medium speed range, and drew continual interest as a tactical airlifter design.
Interest in flying wings reemerged in the 1980s due to their potentially low radar cross-sections. Stealth technology relies on shapes that reflect radar waves only in certain directions, thus making it harder to detect. This approach eventually led to the Northrop B-2 Spirit stealth bomber (pictured). The flying wing's aerodynamics are not the primary concern. Computer-controlled fly-by-wire systems compensated for many of the aerodynamic drawbacks, enabling an efficient and stable long-range aircraft.
Blended wing body
Blended wing body aircraft have a flattened airfoil-shaped body, which produces most of the lift to keep itself aloft, and distinct and separate wing structures, though the wings are blended with the body.
Blended wing bodied aircraft incorporate design features from both fuselage and flying wing designs. The purported advantages of the blended wing body approach are efficient, high-lift wings and a wide, airfoil-shaped body. This enables the entire craft to contribute to lift generation with potentially increased fuel economy.
Lifting body | Fixed-wing aircraft | Wikipedia | 500 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
A lifting body is a configuration in which the body produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing. Whereas a flying wing seeks to maximize cruise efficiency at subsonic speeds by eliminating non-lifting surfaces, lifting bodies generally minimize the drag and structure of a wing for subsonic, supersonic, and hypersonic flight, or, spacecraft re-entry. All of these flight regimes pose challenges for flight stability.
Lifting bodies were a major area of research in the 1960s and 1970s as a means to build small and lightweight manned spacecraft. The US built lifting body rocket planes to test the concept, as well as several rocket-launched re-entry vehicles. Interest waned as the US Air Force lost interest in the manned mission, and major development ended during the Space Shuttle design process when it became clear that highly shaped fuselages made it difficult to fit fuel tanks.
Empennage and foreplane
The classic airfoil section wing is unstable in flight. Flexible-wing planes often rely on an anchor line or the weight of a pilot hanging beneath to maintain the correct attitude. Some free-flying types use an adapted airfoil that is stable, or other mechanisms including electronic artificial stability.
In order to achieve trim, stability, and control, most fixed-wing types have an empennage comprising a fin and rudder that act horizontally, and a tailplane and elevator that act vertically. This is so common that it is known as the conventional layout. Sometimes two or more fins are spaced out along the tailplane.
Some types have a horizontal "canard" foreplane ahead of the main wing, instead of behind it. This foreplane may contribute to the trim, stability or control of the aircraft, or to several of these.
Aircraft controls
Kite control
Kites are controlled by one or more tethers.
Free-flying aircraft controls | Fixed-wing aircraft | Wikipedia | 393 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Gliders and airplanes have sophisticated control systems, especially if they are piloted.
The controls allow the pilot to direct the aircraft in the air and on the ground. Typically these are:
The yoke or joystick controls rotation of the plane about the pitch and roll axes. A yoke resembles a steering wheel. The pilot can pitch the plane down by pushing on the yoke or joystick, and pitch the plane up by pulling on it. Rolling the plane is accomplished by turning the yoke in the direction of the desired roll, or by tilting the joystick in that direction.
Rudder pedals control rotation of the plane about the yaw axis. Two pedals pivot so that when one is pressed forward the other moves backward, and vice versa. The pilot presses on the right rudder pedal to make the plane yaw to the right, and pushes on the left pedal to make it yaw to the left. The rudder is used mainly to balance the plane in turns, or to compensate for winds or other effects that push the plane about the yaw axis.
On powered types, an engine stop control ("fuel cutoff", for example) and, usually, a Throttle or thrust lever and other controls, such as a fuel-mixture control (to compensate for air density changes with altitude change).
Other common controls include:
Flap levers, which are used to control the deflection position of flaps on the wings.
Spoiler levers, which are used to control the position of spoilers on the wings, and to arm their automatic deployment in planes designed to deploy them upon landing. The spoilers reduce lift for landing.
Trim controls, which usually take the form of knobs or wheels and are used to adjust pitch, roll, or yaw trim. These are often connected to small airfoils on the trailing edge of the control surfaces and are called "trim tabs". Trim is used to reduce the amount of pressure on the control forces needed to maintain a steady course.
On wheeled types, brakes are used to slow and stop the plane on the ground, and sometimes for turns on the ground.
A craft may have two pilot seats with dual controls, allowing two to take turns.
The control system may allow full or partial automation, such as an autopilot, a wing leveler, or a flight management system. An unmanned aircraft has no pilot and is controlled remotely or via gyroscopes, computers/sensors or other forms of autonomous control. | Fixed-wing aircraft | Wikipedia | 503 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Cockpit instrumentation
On manned fixed-wing aircraft, instruments provide information to the pilots, including flight, engines, navigation, communications, and other aircraft systems that may be installed.
The six basic instruments, sometimes referred to as the six pack, are:
The airspeed indicator (ASI) shows the speed at which the plane is moving through the air.
The attitude indicator (AI), sometimes called the artificial horizon, indicates the exact orientation of the aircraft about its pitch and roll axes.
The altimeter indicates the altitude or height of the plane above mean sea level (AMSL).
The vertical speed indicator (VSI), or variometer, shows the rate at which the plane is climbing or descending.
The heading indicator (HI), sometimes called the directional gyro (DG), shows the magnetic compass orientation of the fuselage. The direction is affected by wind conditions and magnetic declination.
The turn coordinator (TC), or turn and bank indicator, helps the pilot to control the plane in a coordinated attitude while turning.
Other cockpit instruments include:
A two-way radio, to enable communications with other planes and with air traffic control.
A horizontal situation indicator (HSI) indicates the position and movement of the plane as seen from above with respect to the ground, including course/heading and other information.
Instruments showing the status of the plane's engines (operating speed, thrust, temperature, and other variables).
Combined display systems such as primary flight displays or navigation aids.
Information displays such as onboard weather radar displays.
A radio direction finder (RDF), to indicate the direction to one or more radio beacons, which can be used to determine the plane's position.
A satellite navigation (satnav) system, to provide an accurate position.
Some or all of these instruments may appear on a computer display and be operated with touches, ala a phone. | Fixed-wing aircraft | Wikipedia | 384 | 46770 | https://en.wikipedia.org/wiki/Fixed-wing%20aircraft | Technology | Aviation | null |
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring. While processes such as insemination or pollination, which happen before the fusion of gametes, are also sometimes informally referred to as fertilisation, these are technically separate processes. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms, the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.
History
In antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic.
In 1784, Spallanzani established the need of interaction between the female's ovum and male's sperm to form a zygote in frogs. In 1827, Karl Ernst von Baer observed a therian mammalian egg for the first time. Oscar Hertwig (1876), in Germany, described the fusion of nuclei of spermatozoa and of ova from sea urchin.
Evolution
The evolution of fertilisation is related to the origin of meiosis, as both are part of sexual reproduction, originated in eukaryotes. One hypothesis states that meiosis originated from mitosis.
Fertilisation in plants | Fertilisation | Wikipedia | 335 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
The gametes that participate in fertilisation of plants are the sperm (male) and the egg (female) cell. Various plant groups have differing methods by which the gametes produced by the male and female gametophytes come together and are fertilised. In bryophytes and pteridophytic land plants, fertilisation of the sperm and egg takes place within the archegonium. In seed plants, the male gametophyte is formed within a pollen grain. After pollination, the pollen grain germinates, and a pollen tube grows and penetrates the ovule through a tiny pore called a micropyle. The sperm are transferred from the pollen through the pollen tube to the ovule where the egg is fertilised. In flowering plants, two sperm cells are released from the pollen tube, and a second fertilisation event occurs involving the second sperm cell and the central cell of the ovule, which is a second female gamete.
Pollen tube growth
Unlike animal sperm which is motile, the sperm of most seed plants is immotile and relies on the pollen tube to carry it to the ovule where the sperm is released. The pollen tube penetrates the stigma and elongates through the extracellular matrix of the style before reaching the ovary. Then near the receptacle, it breaks through the ovule through the micropyle (an opening in the ovule wall) and the pollen tube "bursts" into the embryo sac, releasing sperm. The growth of the pollen tube has been believed to depend on chemical cues from the pistil, however these mechanisms were poorly understood until 1995. Work done on tobacco plants revealed a family of glycoproteins called TTS proteins that enhanced growth of pollen tubes. Pollen tubes in a sugar free pollen germination medium and a medium with purified TTS proteins both grew. However, in the TTS medium, the tubes grew at a rate 3x that of the sugar-free medium. TTS proteins were also placed on various locations of semi in vivo pollinated pistils, and pollen tubes were observed to immediately extend toward the proteins. Transgenic plants lacking the ability to produce TTS proteins had slower pollen tube growth and reduced fertility. | Fertilisation | Wikipedia | 472 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
Rupture of pollen tube
The rupture of the pollen tube to release sperm in Arabidopsis has been shown to depend on a signal from the female gametophyte. Specific proteins called FER protein kinases present in the ovule control the production of highly reactive derivatives of oxygen called reactive oxygen species (ROS). ROS levels have been shown via GFP to be at their highest during floral stages when the ovule is the most receptive to pollen tubes, and lowest during times of development and following fertilisation. High amounts of ROS activate Calcium ion channels in the pollen tube, causing these channels to take up Calcium ions in large amounts. This increased uptake of calcium causes the pollen tube to rupture, and release its sperm into the ovule. Pistil feeding assays in which plants were fed diphenyl iodonium chloride (DPI) suppressed ROS concentrations in Arabidopsis, which in turn prevented pollen tube rupture.
Flowering plants
After being fertilised, the ovary starts to swell and develop into the fruit. With multi-seeded fruits, multiple grains of pollen are necessary for syngamy with each ovule. The growth of the pollen tube is controlled by the vegetative (or tube) cytoplasm. Hydrolytic enzymes are secreted by the pollen tube that digest the female tissue as the tube grows down the stigma and style; the digested tissue is used as a nutrient source for the pollen tube as it grows. During pollen tube growth towards the ovary, the generative nucleus divides to produce two separate sperm nuclei (haploid number of chromosomes) – a growing pollen tube therefore contains three separate nuclei, two sperm and one tube. The sperms are interconnected and dimorphic, the large one, in a number of plants, is also linked to the tube nucleus and the interconnected sperm and the tube nucleus form the "male germ unit". | Fertilisation | Wikipedia | 405 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
Double fertilisation is the process in angiosperms (flowering plants) in which two sperm from each pollen tube fertilise two cells in a female gametophyte (sometimes called an embryo sac) that is inside an ovule. After the pollen tube enters the gametophyte, the pollen tube nucleus disintegrates and the two sperm cells are released; one of the two sperm cells fertilises the egg cell (at the bottom of the gametophyte near the micropyle), forming a diploid (2n) zygote. This is the point when fertilisation actually occurs; pollination and fertilisation are two separate processes. The nucleus of the other sperm cell fuses with two haploid polar nuclei (contained in the central cell) in the centre of the gametophyte. The resulting cell is triploid (3n). This triploid cell divides through mitosis and forms the endosperm, a nutrient-rich tissue, inside the seed. The two central-cell maternal nuclei (polar nuclei) that contribute to the endosperm arise by mitosis from the single meiotic product that also gave rise to the egg. Therefore, maternal contribution to the genetic constitution of the triploid endosperm is double that of the embryo.
One primitive species of flowering plant, Nuphar polysepala, has endosperm that is diploid, resulting from the fusion of a sperm with one, rather than two, maternal nuclei. It is believed that early in the development of angiosperm lineages, there was a duplication in this mode of reproduction, producing seven-celled/eight-nucleate female gametophytes, and triploid endosperms with a 2:1 maternal to paternal genome ratio.
In many plants, the development of the flesh of the fruit is proportional to the percentage of fertilised ovules. For example, with watermelon, about a thousand grains of pollen must be delivered and spread evenly on the three lobes of the stigma to make a normal sized and shaped fruit.
Self-pollination and outcrossing | Fertilisation | Wikipedia | 451 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
Outcrossing, or cross-fertilisation, and self-fertilisation represent different strategies with differing benefits and costs. An estimated 48.7% of plant species are either dioecious or self-incompatible obligate outcrossers. It is also estimated that about 42% of flowering plants exhibit a mixed mating system in nature.
In the most common kind of mixed mating system, individual plants produce a single type of flower and fruits may contain self-fertilised, outcrossed or a mixture of progeny types. The transition from cross-fertilisation to self-fertilisation is the most common evolutionary transition in plants, and has occurred repeatedly in many independent lineages. About 10-15% of flowering plants are predominantly self-fertilising.
Under circumstances where pollinators or mates are rare, self-fertilisation offers the advantage of reproductive assurance. Self-fertilisation can therefore result in improved colonisation ability. In some species, self-fertilisation has persisted over many generations. Capsella rubella is a self-fertilising species that became self-compatible 50,000 to 100,000 years ago. Arabidopsis thaliana is a predominantly self-fertilising plant with an out-crossing rate in the wild of less than 0.3%; a study suggested that self-fertilisation evolved roughly a million years ago or more in A. thaliana. In long-established self-fertilising plants, the masking of deleterious mutations and the production of genetic variability is infrequent and thus unlikely to provide a sufficient benefit over many generations to maintain the meiotic apparatus. Consequently, one might expect self-fertilisation to be replaced in nature by an ameiotic asexual form of reproduction that would be less costly. However the actual persistence of meiosis and self-fertilisation as a form of reproduction in long-established self-fertilising plants may be related to the immediate benefit of efficient recombinational repair of DNA damage during formation of germ cells provided by meiosis at each generation.
Fertilisation in animals | Fertilisation | Wikipedia | 455 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
The mechanics behind fertilisation has been studied extensively in sea urchins and mice. This research addresses the question of how the sperm and the appropriate egg find each other and the question of how only one sperm gets into the egg and delivers its contents. There are three steps to fertilisation that ensure species-specificity:
Chemotaxis
Sperm activation/acrosomal reaction
Sperm/egg adhesion
Internal vs. external
Consideration as to whether an animal (more specifically a vertebrate) uses internal or external fertilisation is often dependent on the method of birth. Oviparous animals laying eggs with thick calcium shells, such as chickens, or thick leathery shells generally reproduce via internal fertilisation so that the sperm fertilises the egg without having to pass through the thick, protective, tertiary layer of the egg. Ovoviviparous and viviparous animals also use internal fertilisation. Although some organisms reproduce via amplexus, they may still use internal fertilisation, as with some salamanders. Advantages of internal fertilisation include minimal waste of gametes, greater chance of individual egg fertilisation, longer period of egg protection, and selective fertilisation. Many females have the ability to store sperm for extended periods of time and can fertilise their eggs at their own desire.
Oviparous animals producing eggs with thin tertiary membranes or no membranes at all, on the other hand, use external fertilisation methods. Such animals may be more precisely termed ovuliparous. External fertilisation is advantageous in that it minimises contact (which decreases the risk of disease transmission), and greater genetic variation.
Sea urchins
Sperm find the eggs via chemotaxis, a type of ligand/receptor interaction. Resact is a 14 amino acid peptide purified from the jelly coat of A. punctulata that attracts the migration of sperm. | Fertilisation | Wikipedia | 406 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
After finding the egg, the sperm penetrates the jelly coat through a process called sperm activation. In another ligand/receptor interaction, an oligosaccharide component of the egg binds and activates a receptor on the sperm and causes the acrosomal reaction. The acrosomal vesicles of the sperm fuse with the plasma membrane and are released. In this process, molecules bound to the acrosomal vesicle membrane, such as bindin, are exposed on the surface of the sperm. These contents digest the jelly coat and eventually the vitelline membrane. In addition to the release of acrosomal vesicles, there is explosive polymerisation of actin to form a thin spike at the head of the sperm called the acrosomal process.
The sperm binds to the egg through another ligand reaction between receptors on the vitelline membrane. The sperm surface protein bindin, binds to a receptor on the vitelline membrane identified as EBR1.
Fusion of the plasma membranes of the sperm and egg are likely mediated by bindin. At the site of contact, fusion causes the formation of a fertilisation cone.
Mammals
Male mammals internally fertilise females and ejaculate semen through the penis during copulation. After ejaculation, many sperm move to the upper vagina (via contractions from the vagina) through the cervix and across the length of the uterus to meet the ovum. In cases where fertilisation occurs, the female usually ovulates during a period that extends from hours before copulation to a few days after; therefore, in most mammals, it is more common for ejaculation to precede ovulation than vice versa. | Fertilisation | Wikipedia | 361 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
When sperm are deposited into the anterior vagina, they are not capable of fertilisation (i.e., non-capacitated) and are characterised by slow linear motility patterns. This motility, combined with muscular contractions enables sperm transport towards the uterus and oviducts. There is a pH gradient within the micro-environment of the female reproductive tract such that the pH near the vaginal opening is lower (approximately 5) than the oviducts (approximately 8). The sperm-specific pH-sensitive calcium transport protein called CatSper increases the sperm cell permeability to calcium as it moves further into the reproductive tract. Intracellular calcium influx contributes to sperm capacitation and hyperactivation, causing a more violent and rapid non-linear motility pattern as sperm approach the oocyte. The capacitated spermatozoon and the oocyte meet and interact in the ampulla of the fallopian tube. Rheotaxis, thermotaxis and chemotaxis are known mechanisms that guide sperm towards the egg during the final stage of sperm migration. Spermatozoa respond (see Sperm thermotaxis) to the temperature gradient of ~2 °C between the oviduct and the ampulla, and chemotactic gradients of progesterone have been confirmed as the signal emanating from the cumulus oophorus cells surrounding rabbit and human oocytes. Capacitated and hyperactivated sperm respond to these gradients by changing their behaviour and moving towards the cumulus-oocyte complex. Other chemotactic signals such as formyl Met-Leu-Phe (fMLF) may also guide spermatozoa. | Fertilisation | Wikipedia | 356 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
The zona pellucida, a thick layer of extracellular matrix that surrounds the egg and is similar to the role of the vitelline membrane in sea urchins, binds the sperm. Unlike sea urchins, the sperm binds to the egg before the acrosomal reaction. ZP3, a glycoprotein in the zona pellucida, is responsible for egg/sperm adhesion in humans. The receptor galactosyltransferase (GalT) binds to the N-acetylglucosamine residues on the ZP3 and is important for binding with the sperm and activating the acrosome reaction. ZP3 is sufficient though unnecessary for sperm/egg binding. Two additional sperm receptors exist: a 250kD protein that binds to an oviduct secreted protein, and SED1, which independently binds to the zona. After the acrosome reaction, the sperm is believed to remain bound to the zona pellucida through exposed ZP2 receptors. These receptors are unknown in mice but have been identified in guinea pigs.
In mammals, the binding of the spermatozoon to the GalT initiates the acrosome reaction. This process releases the hyaluronidase that digests the matrix of hyaluronic acid in the vestments around the oocyte. Additionally, heparin-like glycosaminoglycans (GAGs) are released near the oocyte that promote the acrosome reaction. Fusion between the oocyte plasma membranes and sperm follows and allows the sperm nucleus, the typical centriole, and atypical centriole that is attached to the flagellum, but not the mitochondria, to enter the oocyte. The protein CD9 likely mediates this fusion in mice (the binding homolog). The egg "activates" itself upon fusing with a single sperm cell and thereby changes its cell membrane to prevent fusion with other sperm. Zinc atoms are released during this activation.
This process ultimately leads to the formation of a diploid cell called a zygote. The zygote divides to form a blastocyst and, upon entering the uterus, implants in the endometrium, beginning pregnancy. Embryonic implantation not in the uterine wall results in an ectopic pregnancy that can kill the mother. | Fertilisation | Wikipedia | 500 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
In such animals as rabbits, coitus induces ovulation by stimulating the release of the pituitary hormone gonadotropin; this release greatly increases the likelihood of pregnancy.
Humans
Fertilisation in humans is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube, producing a single celled zygote, the first stage of life in the development of a genetically unique organism, and initiating embryonic development. Scientists discovered the dynamics of human fertilisation in the nineteenth century.
The term conception commonly refers to "the process of becoming pregnant involving fertilisation or implantation or both". Its use makes it a subject of semantic arguments about the beginning of pregnancy, typically in the context of the abortion debate.
Upon gastrulation, which occurs around 16 days after fertilisation, the implanted blastocyst develops three germ layers, the endoderm, the ectoderm and the mesoderm, and the genetic code of the father becomes fully involved in the development of the embryo; later twinning is impossible. Additionally, interspecies hybrids survive only until gastrulation and cannot further develop.
However, some human developmental biology literature refers to the conceptus and such medical literature refers to the "products of conception" as the post-implantation embryo and its surrounding membranes. The term "conception" is not usually used in scientific literature because of its variable definition and connotation.
Insects
Insects in different groups, including the Odonata (dragonflies and damselflies) and the Hymenoptera (ants, bees, and wasps) practise delayed fertilisation. Among the Odonata, females may mate with multiple males, and store sperm until the eggs are laid. The male may hover above the female during egg-laying (oviposition) to prevent her from mating with other males and replacing his sperm; in some groups such as the darters, the male continues to grasp the female with his claspers during egg-laying, the pair flying around in tandem. Among social Hymenoptera, honeybee queens mate only on mating flights, in a short period lasting some days; a queen may mate with eight or more drones. She then stores the sperm for the rest of her life, perhaps for five years or more.
Fertilisation in fungi | Fertilisation | Wikipedia | 493 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
In many fungi (except chytrids), as in some protists, fertilisation is a two step process. First, the cytoplasms of the two gamete cells fuse (called plasmogamy), producing a dikaryotic or heterokaryotic cell with multiple nuclei. This cell may then divide to produce dikaryotic or heterokaryotic hyphae. The second step of fertilisation is karyogamy, the fusion of the nuclei to form a diploid zygote.
In chytrid fungi, fertilisation occurs in a single step with the fusion of gametes, as in animals and plants.
Fertilisation in protists
Fertilisation in protozoa
There are three types of fertilisation processes in protozoa:
gametogamy;
autogamy;
gamontogamy.
Fertilisation in algae
Algae, like some land plants, undergo alternation of generations. Some algae are isomorphic, where both the sporophyte (2n) and gameteophyte (n) are the same morphologically. When algae reproduction is described as oogamous, the male and female gametes are different morphologically, where there is a large non-motile egg for female gametes, and the male gamete are uniflagellate (motile). Via the process of syngamy, these will form a new zygote, regenerating the sporophyte generation again.
Fertilisation and genetic recombination
Meiosis results in a random segregation of the genes that each parent contributes. Each parent organism is usually identical save for a fraction of their genes; each gamete is therefore genetically unique. At fertilisation, parental chromosomes combine. In humans, (2²²)² = 17.6x1012 chromosomally different zygotes are possible for the non-sex chromosomes, even assuming no chromosomal crossover. If crossover occurs once, then on average (4²²)² = 309x1024 genetically different zygotes are possible for every couple, not considering that crossover events can take place at most points along each chromosome. The X and Y chromosomes undergo no crossover events and are therefore excluded from the calculation. The mitochondrial DNA is only inherited from the maternal parent. | Fertilisation | Wikipedia | 496 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
The sperm aster and zygote centrosomes
Shortly after the sperm fuse with the egg, the two sperm centrioles form the embryo first centrosome and microtubule aster. The sperm centriole, found near the male pronucleus, recruit egg Pericentriolar material proteins forming the zygote first centrosome. This centrosome nucleates microtubules in the shape of stars called astral microtubules. The microtubules span the whole valium of the egg, allowing the egg pronucleus to use the cables to get to the male pronucleus. As the male and female pronuclei approach each other, the single centrosome split into two centrosomes located in the interphase between the pronuclei. Then the centrosome via the astral microtubules polarises the genome inside the pronuclei.
Parthenogenesis
Organisms that normally reproduce sexually can also reproduce via parthenogenesis, wherein an unfertilised female gamete produces viable offspring. These offspring may be clones of the mother, or in some cases genetically differ from her but inherit only part of her DNA. Parthenogenesis occurs in many plants and animals and may be induced in others through a chemical or electrical stimulus to the egg cell. In 2004, Japanese researchers led by Tomohiro Kono succeeded after 457 attempts to merge the ova of two mice by blocking certain proteins that would normally prevent the possibility; the resulting embryo normally developed into a mouse.
Allogamy and autogamy
Allogamy, which is also known as cross-fertilisation, refers to the fertilisation of an egg cell from one individual with the male gamete of another.
Autogamy which is also known as self-fertilisation, occurs in such hermaphroditic organisms as plants and flatworms; therein, two gametes from one individual fuse.
Other variants of bisexual reproduction
Some relatively unusual forms of reproduction are:
Gynogenesis: A sperm stimulates the egg to develop without fertilisation or syngamy. The sperm may enter the egg.
Hybridogenesis: One genome is eliminated to produce haploid eggs.
Canina meiosis: (sometimes called "permanent odd polyploidy") one genome is transmitted in the Mendelian fashion, others are transmitted clonally.
Benefits of cross-fertilisation | Fertilisation | Wikipedia | 504 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
The major benefit of cross-fertilisation is generally thought to be the avoidance of inbreeding depression. Charles Darwin, in his 1876 book The Effects of Cross and Self Fertilisation in the Vegetable Kingdom (pages 466-467) summed up his findings in the following way.
"It has been shown in the present volume that the offspring from the union of two distinct individuals, especially if their progenitors have been subjected to very different conditions, have an immense advantage in height, weight, constitutional vigour and fertility over the self-fertilised offspring from one of the same parents. And this fact is amply sufficient to account for the development of the sexual elements, that is, for the genesis of the two sexes."
In addition, it is thought by some, that a long-term advantage of out-crossing in nature is increased genetic variability that promotes adaptation or avoidance of extinction (see Genetic variability). | Fertilisation | Wikipedia | 194 | 46828 | https://en.wikipedia.org/wiki/Fertilisation | Biology and health sciences | Health and fitness | null |
Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver. FHSS is used to avoid interference, to prevent eavesdropping, and to enable code-division multiple access (CDMA) communications.
The frequency band is divided into smaller sub-bands. Signals rapidly change ("hop") their carrier frequencies among the center frequencies of these sub-bands in a determined order. Interference at a specific frequency will affect the signal only during a short interval.
FHSS offers four main advantages over a fixed-frequency transmission:
FHSS signals are highly resistant to narrowband interference because the signal hops to a different frequency band.
Signals are difficult to intercept if the frequency-hopping pattern is not known.
Jamming is also difficult if the pattern is unknown; the signal can be jammed only for a single hopping period if the spreading sequence is unknown.
FHSS transmissions can share a frequency band with many types of conventional transmissions with minimal mutual interference. FHSS signals add minimal interference to narrowband communications, and vice versa.
Usage
Military
Spread-spectrum signals are highly resistant to deliberate jamming unless the adversary has knowledge of the frequency-hopping pattern. Military radios generate the frequency-hopping pattern under the control of a secret Transmission Security Key (TRANSEC) that the sender and receiver share in advance. This key is generated by devices such as the KY-57 Speech Security Equipment. United States military radios that use frequency hopping include the JTIDS/MIDS family, the HAVE QUICK Aeronautical Mobile communications system, and the SINCGARS Combat Net Radio, Link-16.
Civilian
In the US, since the Federal Communications Commission (FCC) amended rules to allow FHSS systems in the unregulated 2.4 GHz band, many consumer devices in that band have employed various FHSS modes. eFCC CFR 47 part 15.247 covers the regulations in the US for 902–928 MHz, 2400–2483.5 MHz, and 5725–5850 MHz bands, and the requirements for frequency hopping. | Frequency-hopping spread spectrum | Wikipedia | 451 | 46890 | https://en.wikipedia.org/wiki/Frequency-hopping%20spread%20spectrum | Technology | Telecommunications | null |
Some walkie-talkies that employ FHSS technology have been developed for unlicensed use on the 900 MHz band. FHSS technology is also used in many hobby transmitters and receivers used for radio-controlled model cars, airplanes, and drones. A type of multiple access is achieved allowing hundreds of transmitter/receiver pairs to be operated simultaneously on the same band, in contrast to previous FM or AM radio-controlled systems that had limited simultaneous channels.
Technical considerations
The overall bandwidth required for frequency hopping is much wider than that required to transmit the same information using only one carrier frequency. But because transmission occurs only on a small portion of this bandwidth at any given time, the instantaneous interference bandwidth is really the same. While providing no extra protection against wideband thermal noise, the frequency-hopping approach reduces the degradation caused by narrowband interference sources.
One of the challenges of frequency-hopping systems is to synchronize the transmitter and receiver. One approach is to have a guarantee that the transmitter will use all the channels in a fixed period of time. The receiver can then find the transmitter by picking a random channel and listening for valid data on that channel. The transmitter's data is identified by a special sequence of data that is unlikely to occur over the segment of data for this channel, and the segment can also have a checksum for integrity checking and further identification. The transmitter and receiver can use fixed tables of frequency-hopping patterns, so that once synchronized they can maintain communication by following the table.
In the US, FCC part 15 on unlicensed spread spectrum systems in the 902–928 MHz and 2.4 GHz bands permits more power than is allowed for non-spread-spectrum systems. Both FHSS and direct-sequence spread-spectrum (DSSS) systems can transmit at 1 watt, a thousandfold increase from the 1 milliwatt limit on non-spread-spectrum systems. The FCC also prescribes a minimum number of frequency channels and a maximum dwell time for each channel.
Origins
In 1899, Guglielmo Marconi experimented with frequency-selective reception in an attempt to minimise interference. | Frequency-hopping spread spectrum | Wikipedia | 433 | 46890 | https://en.wikipedia.org/wiki/Frequency-hopping%20spread%20spectrum | Technology | Telecommunications | null |
The earliest mentions of frequency hopping in open literature are in US patent 725,605, awarded to Nikola Tesla on March 17, 1903, and in radio pioneer Jonathan Zenneck's book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck writes that Telefunken had already tried it. Nikola Tesla doesn't mention the phrase "frequency hopping" directly, but certainly alludes to it. Entitled Method of Signaling, the patent describes a system that would enable radio communication without any danger of the signals or messages being disturbed, intercepted, interfered with in any way.
The German military made limited use of frequency hopping for communication between fixed command points in World War I to prevent eavesdropping by British forces, who did not have the technology to follow the sequence. Jonathan Zenneck's book Wireless Telegraphy was originally published in German in 1908, but was translated into English in 1915 as the enemy started using frequency hopping on the front line.
In 1920, Otto B. Blackwell, De Loss K. Martin, and Gilbert S. Vernam filed a patent application for a "Secrecy Communication System", granted as U.S. Patent 1,598,673 in 1926. This patent described a method of transmitting signals on multiple frequencies in a random manner for secrecy, anticipating key features of later frequency hopping systems.
A Polish engineer and inventor, Leonard Danilewicz, claimed to have suggested the concept of frequency hopping in 1929 to the Polish General Staff, but it was rejected.
In 1932, was awarded to Willem Broertjes, named "Method of maintaining secrecy in the transmission of wireless telegraphic messages", which describes a system where "messages are transmitted by means of a group of frequencies... known to the sender and receiver alone, and alternated at will during transmission of the messages".
During World War II, the US Army Signal Corps was inventing a communication system called SIGSALY, which incorporated spread spectrum in a single frequency context. But SIGSALY was a top-secret communications system, so its existence was not known until the 1980s.
In 1942, actress Hedy Lamarr and composer George Antheil received for their "Secret Communications System", an early version of frequency hopping using a piano-roll to switch among 88 frequencies to make radio-guided torpedoes harder for enemies to detect or jam. They then donated the patent to the U.S. Navy. | Frequency-hopping spread spectrum | Wikipedia | 497 | 46890 | https://en.wikipedia.org/wiki/Frequency-hopping%20spread%20spectrum | Technology | Telecommunications | null |
Frequency-hopping ideas may have been rediscovered in the 1950s during patent searches when private companies were independently developing direct-sequence Code Division Multiple Access, a non-frequency-hopping form of spread-spectrum. In 1957, engineers at Sylvania Electronic Systems Division adopted a similar idea, using the recently invented transistor instead of Lamarr's and Antheil's clockwork technology. In 1962, the US Navy utilized Sylvania Electronic Systems Division's work during the Cuban Missile Crisis.
A practical application of frequency hopping was developed by Ray Zinn, co-founder of Micrel Corporation. Zinn developed a method allowing radio devices to operate without the need to synchronize a receiver with a transmitter. Using frequency hopping and sweep modes, Zinn's method is primarily applied in low data rate wireless applications such as utility metering, machine and equipment monitoring and metering, and remote control. In 2006 Zinn received for his "Wireless device and method using frequency hopping and sweep modes."
Variations
Adaptive frequency-hopping spread spectrum (AFH) as used in Bluetooth improves resistance to radio frequency interference by avoiding crowded frequencies in the hopping sequence. This sort of adaptive transmission is easier to implement with FHSS than with DSSS.
The key idea behind AFH is to use only the "good" frequencies and avoid the "bad" ones—those experiencing frequency selective fading, those on which a third party is trying to communicate, or those being actively jammed. Therefore, AFH should be complemented by a mechanism for detecting good and bad channels.
But if the radio frequency interference is itself dynamic, then AFH's strategy of "bad channel removal" may not work well. For example, if there are several colocated frequency-hopping networks (as Bluetooth Piconet), they are mutually interfering and AFH's strategy fails to avoid this interference.
The problem of dynamic interference, gradual reduction of available hopping channels and backward compatibility with legacy Bluetooth devices was resolved in version 1.2 of the Bluetooth Standard (2003). Such a situation can often happen in the scenarios that use unlicensed spectrum.
In addition, dynamic radio frequency interference is expected to occur in the scenarios related to cognitive radio, where the networks and the devices should exhibit frequency-agile operation.
Chirp modulation can be seen as a form of frequency-hopping that simply scans through the available frequencies in consecutive order to communicate. | Frequency-hopping spread spectrum | Wikipedia | 494 | 46890 | https://en.wikipedia.org/wiki/Frequency-hopping%20spread%20spectrum | Technology | Telecommunications | null |
Frequency hopping can be superimposed on other modulations or waveforms to enhance the system performance. | Frequency-hopping spread spectrum | Wikipedia | 20 | 46890 | https://en.wikipedia.org/wiki/Frequency-hopping%20spread%20spectrum | Technology | Telecommunications | null |
Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine. Lutrinae is a branch of the Mustelidae family, which includes weasels, badgers, mink, and wolverines, among other animals.
Otters' habitats include dens known as holts or couches, with their social structure described by terms such as dogs or boars for males, bitches or sows for females, and pups or cubs for offspring. Groups of otters can be referred to as a bevy, family, lodge, romp, or raft when in water, indicating their social and playful characteristics. Otters are known for their distinct feces, termed spraints, which can vary in smell from freshly mown hay to putrefied fish.
Otters exhibit a varied life cycle with a gestation period of about 60–86 days, and offspring typically stay with their family for a year. They can live up to 16 years, with their diet mainly consisting of fish and sometimes frogs, birds, or shellfish, depending on the species. Otters are distinguished by their long, slim bodies, powerful webbed feet for swimming, and their dense fur, which keeps them warm and buoyant in water. They are playful animals, engaging in activities like sliding into water on natural slides and playing with stones.
There are 13 known species of otters, ranging in size and habitat preferences, with some species adapted to cold waters requiring a high metabolic rate for warmth. Otter-human interactions have varied over time, with otters being hunted for their pelts, used in fishing practices in southern Bangladesh, and occasionally attacking humans, though such incidents are rare and often a result of provocation. Otters hold a place in various cultures' mythology and religion, symbolizing different attributes and stories, from Norse mythology to Native American totems and Asian folklore, where they are sometimes believed to possess shapeshifting abilities.
Etymology
The word otter derives from the Old English word or . This and cognate words in other Indo-European languages ultimately stem from the Proto-Indo-European root , which also gave rise to the English word "water". | Otter | Wikipedia | 455 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
Terminology
An otter's den is called a holt, or couch. Male otters are called dogs or boars; females are called bitches or sows; and their offspring are called pups or cubs. The collective nouns for otters are bevy, family, lodge, romp (being descriptive of their often playful nature), or, when in water, raft.
The feces of otters are typically identified by their distinctive aroma, the smell of which has been described as ranging from freshly mown hay to putrefied fish; these are known as spraints.
Life cycle
The gestation period in otters is about 60 to 86 days. The newborn pup is cared for by the bitch, dog, and older offspring. Female otters reach sexual maturity at approximately two years of age and males at approximately three years. The holt is built under tree roots or a rocky cairn, more common in Scotland. It is lined with moss and grass.
After one month, the pup can leave the holt and after two months, it is able to swim. The pup lives with its family for approximately one year. Otters live up to 16 years; they are by nature playful, and frolic in the water with their pups. Its usual source of food is fish, and further downriver, eels, but it may sample frogs and birds.
Description
Otters have long, slim bodies and relatively short limbs. Their most striking anatomical features are the powerful webbed feet used to swim, and their seal-like abilities for holding breath underwater. Most have sharp claws on their feet and all except the sea otter have long, muscular tails. The 13 species range in adult size from in length and in weight. The Asian small-clawed otter is the smallest otter species and the giant otter and sea otter are the largest. They have very soft, insulated underfur, which is protected by an outer layer of long guard hairs. This traps a layer of air which keeps them dry, warm, and somewhat buoyant under water.
Several otter species live in cold waters and have high metabolic rates to help keep them warm. Eurasian otters must eat 15% of their body weight each day, and sea otters 20 to 25%, depending on the temperature. In water as warm as , an otter needs to catch of fish per hour to survive. Most species hunt for three to five hours each day and nursing mothers up to eight hours each day. | Otter | Wikipedia | 497 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
Feeding
For most otters, fish is the staple of their diet. This is often supplemented by frogs, crayfish and crabs. Some otters are experts at opening shellfish, and others will feed on available small mammals or birds. Prey-dependence leaves otters very vulnerable to prey depletion. Sea otters are hunters of clams, sea urchins and other shelled creatures. They are notable for their ability to use stones to break open shellfish on their bellies. This skill must be learned by the young.
Otters are active hunters, chasing prey in the water or searching the beds of rivers, lakes or the seas. Most species live beside water, but river otters usually enter it only to hunt or travel, otherwise spending much of their time on land to prevent their fur becoming waterlogged. Sea otters are considerably more aquatic and live in the ocean for most of their lives.
Otters are playful animals and appear to engage in various behaviors for sheer enjoyment, such as making waterslides and sliding on them into the water. They may also find and play with small stones. Different species vary in their social structure, some being largely solitary, while others live in groups – in a few species these groups may be fairly large.
Species
Extant species
Extinct species
Subfamily Lutrinae
Genus Lutra
†Lutra castiglionis – Corsica, Pleistocene
†Lutra euxena – Malta, Pleistocene
†Japanese otter (Lutra nippon) – Japan, extinct c. 1979 Genus Lutrogale †Lutrogale cretensis Genus Enhydra †Enhydra macrodonta †Enhydra reevei Genus †Algarolutra – Corsica and Sardinia, Pleistocene
Genus †Cyrnaonyx – Europe, Pleistocene
Genus †Enhydriodon – Ethiopia, Late Miocene to Pliocene
Genus †Enhydritherium – North America, Late Miocene to Early Pliocene | Otter | Wikipedia | 391 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
Genus †Lutraeximia – Italy, Pleistocene
Genus †Limnonyx – Germany, Late Miocene
Genus †Megalenhydris – Sardinia, Pleistocene
Genus †Paludolutra – Italy, Late Miocene
Genus †Sardolutra – Sardinia, Pleistocene
Genus †Siamogale – eastern Asia, Late Miocene to Early Pliocene
Genus †Sivaonyx – Asia and Africa, Late Miocene to Early Pliocene
Genus †Teruelictis – Spain, Late Miocene
Genus †Torolutra – Africa, Pliocene
Genus †Tyrrhenolutra – Italy, Late Miocene
Genus †Vishnuonyx – Europe, Asia and Africa, Late Miocene to Early Pliocene
Relation with humans
Hunting
Otters have been hunted for their pelts from at least the 1700s, although it may have begun well before then. Early hunting methods included darts, arrows, nets and snares but later, traps were set on land and guns used.
There has been a long history of otter pelts being worn around the world. In China it was standard for the royalty to wear robes made from them. People that were financially high in status also wore them. The tails of otters were often made into items for men to wear. These included hats and belts. Even some types of mittens for children have been made from the fur of otters.
Otters have also been hunted using dogs, especially the otterhound. From 1958 to 1963, the 11 otter hunts in England and Wales killed 1,065 otters between them. In such hunts, the hunters notched their poles after every kill. The prized trophy that hunters would take from the otters was the baculum, which would be worn as a tie-pin.
Traffic (the wildlife trade monitoring network) reported that otters are at serious risk in Southeast Asia and have disappeared from parts of their former range. This decline in populations is due to hunting to supply the demand for skins.
Fishing for humans
For many generations, fishermen in southern Bangladesh have bred smooth-coated otters and used them to chase fish into their nets. Once a widespread practice, passed down from father to son throughout many communities in Asia, this traditional use of domesticated wild animals is still in practice in the district of Narail, Bangladesh. | Otter | Wikipedia | 466 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
Attacks on humans
A 2011 review by the IUCN/SSC Otter Specialist Group showed that otter attacks reported between 1875 and 2010 occurred most often in Florida, where human and otter populations have substantially increased since 2000, with the majority involving the North American otter. At least 42 instances of attack were found, including one resulting in death and another case of serious injury. Attacking otters had rabies in 36% of anecdotal reports. 80% of otter bite victims do not seek medical treatment.
Animal welfare groups say that, unless threatened, otters rarely attack humans. In November 2021, about 20 otters ambushed a British man in his 60s during an early morning walk in Singapore Botanic Gardens. Despite weighing over 200 pounds, he was trampled and bitten and could not stand up without help from a nearby rescuer. The man speculated that another runner might have stepped on one of the animals earlier, and wished that there could be more lighting installed at that location.
Religion and mythology
Norse mythology tells of the dwarf Ótr habitually taking the form of an otter. The myth of "Otter's Ransom" is the starting point of the Volsunga saga.
In Irish mythology, the character Lí Ban was turned from a woman into a mermaid, half human and half salmon, and given three hundred years of life to roam the oceans. Her lapdog assumed the form of an otter and shared her prolonged lifetime and her extensive wanderings.
In some Native American cultures, otters are considered totem animals.
The otter is held to be a clean animal belonging to Ahura Mazda in Zoroastrian belief, and taboo to kill.
In popular Korean mythology, it is told that people who see an otter (soodal) will attract 'rain clouds' for the rest of their lives.
In the Buddhist Jataka tales, The Otters and The Wolf, two otters agreed to let a wolf settle their dispute in dividing their caught fish but it was taken away by the cunning wolf.
Japanese folklore
In Japanese, otters are called "kawauso" (). In Japanese folklore, they fool humans in the same way as foxes (kitsune) and tanuki. | Otter | Wikipedia | 437 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
In the Noto region, Ishikawa Prefecture, there are stories where they shapeshift into beautiful women or children wearing checker-patterned clothing. If a human attempts to speak to one, they will answer "oraya" and then answer "araya," and if anybody asks them anything, they say cryptic things like "kawai." There are darker stories, such as one from Kaga Province (now Ishikawa Prefecture) in which an otter that lives in the castle's moat shapeshifts into a woman, invites males, and then kills and eats them.
In the kaidan, essays, and legends of the Edo period like the "Urami Kanawa" (), "Taihei Hyaku Monogatari" (), and the "Shifu Goroku" (), there are tales about strange occurrences like otters that shapeshift into beautiful women and kill men.
In the town of Numatachi, Asa District, Hiroshima Prefecture (now Hiroshima), they are called "tomo no kawauso" () and "ato no kawauso" (). It is said that they shapeshift into bōzu (a kind of monk) and appear before passers-by, and if the passer-by tries to get close and look up, its height steadily increases until it becomes a large bōzu.
In the Tsugaru region, Aomori Prefecture, they are said to possess humans. It is said that those possessed by otters lose their stamina as if their soul has been extracted. They are also said to shapeshift into severed heads and get caught in fishing nets.
In the Kashima District and the Hakui District in Ishikawa Prefecture, they are seen as a yōkai under the name kabuso or kawaso. They perform pranks like extinguishing the fire of the paper lanterns of people who walk on roads at night, shapeshifting into a beautiful woman of 18 or 19 years of age and fooling people, or tricking people and making them try to engage in sumo against a rock or a tree stump. It is said that they speak human words, and sometimes people are called and stopped while walking on roads. | Otter | Wikipedia | 461 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
In the Ishikawa and Kochi Prefectures, they are said to be a type of kappa, and there are stories told about how they engage in sumo with otters. In places like the Hokuriku region, Kii, and Shikoku, the otters are seen as a type of kappa. In the Kagakushū, a dictionary from the Muromachi period, an otter that grew old becomes a kappa.
In an Ainu folktale, in Urashibetsu (in Abashiri, Hokkaido), there are stories where monster otters shapeshift into humans, go into homes where there are beautiful girls, and try to kill the girl and make her its wife.
In China, like in Japan, there are stories where otters shapeshift into beautiful women in old books like In Search of the Supernatural and the Zhenyizhi (). | Otter | Wikipedia | 181 | 46916 | https://en.wikipedia.org/wiki/Otter | Biology and health sciences | Carnivora | null |
Caesarean section, also known as C-section, cesarean, or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen. It is often performed because vaginal delivery would put the mother or child at risk. Reasons for the operation include obstructed labor, twin pregnancy, high blood pressure in the mother, breech birth, shoulder presentation, and problems with the placenta or umbilical cord. A caesarean delivery may be performed based upon the shape of the mother's pelvis or history of a previous C-section. A trial of vaginal birth after C-section may be possible. The World Health Organization recommends that caesarean section be performed only when medically necessary.
A C-section typically takes 45 minutes to an hour. It may be done with a spinal block, where the woman is awake, or under general anesthesia. A urinary catheter is used to drain the bladder, and the skin of the abdomen is then cleaned with an antiseptic. An incision of about 15 cm (6 inches) is then typically made through the mother's lower abdomen. The uterus is then opened with a second incision and the baby delivered. The incisions are then stitched closed. A woman can typically begin breastfeeding as soon as she is out of the operating room and awake. Often, several days are required in the hospital to recover sufficiently to return home.
C-sections result in a small overall increase in poor outcomes in low-risk pregnancies. They also typically take about six weeks to heal from, longer than vaginal birth. The increased risks include breathing problems in the baby and amniotic fluid embolism and postpartum bleeding in the mother. Established guidelines recommend that caesarean sections not be used before 39 weeks of pregnancy without a medical reason. The method of delivery does not appear to have an effect on subsequent sexual function. | Caesarean section | Wikipedia | 404 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
In 2012, about 23 million C-sections were done globally. The international healthcare community has previously considered the rate of 10% and 15% to be ideal for caesarean sections. Some evidence finds a higher rate of 19% may result in better outcomes. More than 45 countries globally have C-section rates less than 7.5%, while more than 50 have rates greater than 27%. Efforts are being made to both improve access to and reduce the use of C-section. In the United States as of 2017, about 32% of deliveries are by C-section. The surgery has been performed at least as far back as 715 BC following the death of the mother, with the baby occasionally surviving. A popular idea is that the Roman statesman Julius Caesar was born via caesarean section and is the namesake of the procedure, but if this is the true etymology, it is based on a misconception: until the modern era, C-sections seem to have been invariably fatal to the mother, and Caesar's mother Aurelia not only survived her son's birth but lived for nearly 50 years afterward. There are many ancient and medieval legends, oral histories, and historical records of laws about C-sections around the world, especially in Europe, the Middle East and Asia. The first recorded successful C-section (where both the mother and the infant survived) was performed on a woman in Switzerland in 1500 by her husband, Jakob Nufer, though this was not recorded until 8 decades later. With the introduction of antiseptics and anesthetics in the 19th century, survival of both the mother and baby, and thus the procedure, became significantly more common.
Uses
Caesarean section (C-section) is recommended when vaginal delivery might pose a risk to the mother or baby. C-sections are also carried out for personal and social reasons on maternal request in some countries. | Caesarean section | Wikipedia | 384 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Medical uses
Complications of labor and factors increasing the risk associated with vaginal delivery include:
Abnormal presentation (breech or transverse positions)
Prolonged labor or a failure to progress (obstructed labour, also known as dystocia)
Fetal distress
Cord prolapse
Uterine rupture or an elevated risk thereof
Uncontrolled hypertension, pre-eclampsia, or eclampsia in the mother
Tachycardia in the mother or baby after amniotic rupture (the waters breaking)
Placenta problems (placenta praevia, placental abruption or placenta accreta)
Failed labor induction
Failed instrumental delivery (by forceps or ventouse (Sometimes, a trial of forceps/ventouse delivery is attempted, and if unsuccessful, the baby will need to be delivered by caesarean section.)
Large baby weighing > 4,000 grams (macrosomia)
Umbilical cord abnormalities (vasa previa, multilobate including bilobate and succenturiate-lobed placentas, velamentous insertion)
Other complications of pregnancy, pre-existing conditions, and concomitant disease, include:
Previous (high risk) fetus
HIV infection of the mother with a high viral load (HIV with a low maternal viral load is not necessarily an indication for caesarean section)
An outbreak of genital herpes in the third trimester (which can cause infection in the baby if born vaginally)
Previous classical (longitudinal) caesarean section
Previous uterine rupture
Prior problems with the healing of the perineum (from previous childbirth or Crohn's disease)
Bicornuate uterus
Rare cases of posthumous birth after the death of the mother
Other
Decreasing experience of accoucheurs with the management of breech presentation. Although obstetricians and midwives are extensively trained in proper procedures for breech presentation deliveries using simulation mannequins, there is decreasing experience with actual vaginal breech delivery, which may increase the risk.
Prevention
The prevalence of caesarean section is generally agreed to be higher than needed in many countries, and physicians are encouraged to actively lower the rate, as a caesarean rate higher than 10–15% is not associated with reductions in maternal or infant mortality rates, although some evidence support that a higher rate of 19% may result in better outcomes. | Caesarean section | Wikipedia | 485 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Some of these efforts are: emphasizing a long latent phase of labor is not abnormal and not a justification for C-section; a new definition of the start of active labor from a cervical dilatation of 4 cm to a dilatation of 6 cm; and allowing women who have previously given birth to push for at least 2 hours, with 3 hours of pushing for women who have not previously given birth, before labor arrest is considered. Physical exercise during pregnancy decreases the risk. Additionally, results from a 2021 systematic review of the evidence on outpatient cervical ripening found that in women with low-risk pregnancies, the risk of cesarean delivery with harms to the mother or child were not significantly different from when done in an inpatient setting.
Risks
Adverse outcomes in low-risk pregnancies occur in 8.6% of vaginal deliveries and 9.2% of caesarean section deliveries.
Mother
In those who are low risk, the risk of death for caesarean sections is 13 per 100,000 vs. for vaginal birth 3.5 per 100,000 in the developed world. The United Kingdom National Health Service gives the risk of death for the mother as three times that of a vaginal birth.
In Canada, the difference in serious morbidity or mortality for the mother (e.g. cardiac arrest, wound hematoma, or hysterectomy) was 1.8 additional cases per 100. The difference in in-hospital maternal death was not significant.
A caesarean section is associated with risks of postoperative adhesions, incisional hernias (which may require surgical correction), and wound infections. If a caesarean is performed in an emergency, the risk of the surgery may be increased due to a number of factors. The patient's stomach may not be empty, increasing the risk of anaesthesia. Other risks include severe blood loss (which may require a blood transfusion) and post-dural-puncture spinal- headaches.
Wound infections occur after caesarean sections at a rate of 3–15%. The presence of chorioamnionitis and obesity predisposes the woman to develop a surgical site infection. | Caesarean section | Wikipedia | 448 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Women who had caesarean sections are more likely to have problems with later pregnancies, and women who want larger families should not seek an elective caesarean unless medical indications to do so exist. The risk of placenta accreta, a potentially life-threatening condition which is more likely to develop where a woman has had a previous caesarean section, is 0.13% after two caesarean sections, but increases to 2.13% after four and then to 6.74% after six or more. Along with this is a similar rise in the risk of emergency hysterectomies at delivery.
Mothers can experience an increased incidence of postnatal depression, and can experience significant psychological trauma and ongoing birth-related post-traumatic stress disorder after obstetric intervention during the birthing process. Factors like pain in the first stage of labor, feelings of powerlessness, intrusive emergency obstetric intervention are important in the subsequent development of psychological issues related to labor and delivery.
Subsequent pregnancies
Women who have had a caesarean for any reason are somewhat less likely to become pregnant again as compared to women who have previously delivered only vaginally.
Women who had just one previous caesarean section are more likely to have problems with their second birth. Delivery after previous caesarean section is by either of two main options:
Vaginal birth after caesarean section (VBAC)
Elective repeat caesarean section (ERCS)
Both have higher risks than a vaginal birth with no previous caesarean section. A vaginal birth after caesarean section (VBAC) confers a higher risk of uterine rupture (5 per 1,000), blood transfusion or endometritis (10 per 1,000), and perinatal death of the child (0.25 per 1,000). Furthermore, 20% to 40% of planned VBAC attempts end in caesarean section being needed, with greater risks of complications in an emergency repeat caesarean section than in an elective repeat caesarean section. On the other hand, VBAC confers less maternal morbidity and a decreased risk of complications in future pregnancies than elective repeat caesarean section.
Adhesions | Caesarean section | Wikipedia | 455 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
There are several steps that can be taken during abdominal or pelvic surgery to minimize postoperative complications, such as the formation of adhesions. Such techniques and principles may include:
Handling all tissue with absolute care
Using powder-free surgical gloves
Controlling bleeding
Choosing sutures and implants carefully
Keeping tissue moist
Preventing infection with antibiotics given intravenously to the mother before skin incision
Despite these proactive measures, adhesion formation is a recognized complication of any abdominal or pelvic surgery. To prevent adhesions from forming after caesarean section, adhesion barrier can be placed during surgery to minimize the risk of adhesions between the uterus and ovaries, the small bowel, and almost any tissue in the abdomen or pelvis. This is not current UK practice, as there is no compelling evidence to support the benefit of this intervention.
Adhesions can cause long-term problems, such as:
Infertility, which may end when adhesions distort the tissues of the ovaries and tubes, impeding the normal passage of the egg (ovum) from the ovary to the uterus. One in five infertility cases may be adhesion related (stoval)
Chronic pelvic pain, which may result when adhesions are present in the pelvis. Almost 50% of chronic pelvic pain cases are estimated to be adhesion related (stoval)
Small bowel obstruction: the disruption of normal bowel flow, which can result when adhesions twist or pull the small bowel.
The risk of adhesion formation is one reason why vaginal delivery is usually considered safer than elective caesarean section where there is no medical indication for section for either maternal or fetal reasons.
Child
Non-medically indicated (elective) childbirth before 39 weeks gestation "carry significant risks for the baby with no known benefit to the mother." Newborn mortality at 37 weeks may be up to 3 times the number at 40 weeks, and is elevated compared to 38 weeks gestation. These early term births were associated with more death during infancy, compared to those occurring at 39 to 41 weeks (full term). Researchers in one study and another review found many benefits to going full term, but no adverse effects in the health of the mothers or babies. | Caesarean section | Wikipedia | 471 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
The American Congress of Obstetricians and Gynecologists and medical policy makers review research studies and find more incidence of suspected or proven sepsis, RDS, hypoglycemia, need for respiratory support, need for NICU admission, and need for hospitalization > 4–5 days. In the case of caesarean sections, rates of respiratory death were 14 times higher in pre-labor at 37 compared with 40 weeks gestation, and 8.2 times higher for pre-labor caesarean at 38 weeks. In this review, no studies found decreased neonatal morbidity due to non-medically indicated (elective) delivery before 39 weeks.
For otherwise healthy twin pregnancies where both twins are head down a trial of vaginal delivery is recommended at between 37 and 38 weeks. Vaginal delivery, in this case, does not worsen the outcome for either infant as compared with caesarean section. There is some controversy on the best method of delivery where the first twin is head first and the second is not, but most obstetricians will recommend normal delivery unless there are other reasons to avoid vaginal birth. When the first twin is not head down, a caesarean section is often recommended. Regardless of whether the twins are delivered by section or vaginally, the medical literature recommends delivery of dichorionic twins at 38 weeks, and monochorionic twins (identical twins sharing a placenta) by 37 weeks due to the increased risk of stillbirth in monochorionic twins who remain in utero after 37 weeks. The consensus is that late preterm delivery of monochorionic twins is justified because the risk of stillbirth for post-37-week delivery is significantly higher than the risks posed by delivering monochorionic twins near term (i.e., 36–37 weeks).
The consensus concerning monoamniotic twins (identical twins sharing an amniotic sac), the highest risk type of twins, is that they should be delivered by caesarean section at or shortly after 32 weeks, since the risks of intrauterine death of one or both twins is higher after this gestation than the risk of complications of prematurity.
In a research study widely publicized, singleton children born earlier than 39 weeks may have developmental problems, including slower learning in reading and math. | Caesarean section | Wikipedia | 479 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Other risks include:
Wet lung (Transient Tachypnea of the Newborn): Failure to pass through the birth canal does not expose the baby to cortisol and epinephrine which typically would reverse the potassium/sodium pumps in the baby's lung. This causes fluid to remain in the lung.
Potential for early delivery and complications: Preterm delivery may be inadvertently carried out if the due-date calculation is inaccurate. One study found an increased complication risk if a repeat elective caesarean section is performed even a few days before the recommended 39 weeks.
Higher infant mortality risk: In caesarean sections performed with no indicated medical risk (singleton at full term in a head-down position with no other obstetric or medical complications), the risk of death in the first 28 days of life has been cited as 1.77 per 1,000 live births among women who had caesarean sections, compared to 0.62 per 1,000 for women who delivered vaginally.
Birth by caesarean section also seems to be associated with worse health outcomes later in life, including overweight or obesity, problems in the immune system, and poor digestive system. However, caesarean deliveries are found to not affect a newborn's risk of developing food allergy. This finding contradicts a previous study that claims babies born via caesarean section have lower levels of Bacteroides that is linked to peanut allergy in infants.
Classification
Caesarean sections have been classified in various ways by different perspectives. One way to discuss all classification systems is to group them by their focus either on the urgency of the procedure (most common), characteristics of the mother, or as a group based on other, less commonly discussed factors.
By urgency
Conventionally, caesarean sections are classified as being either an elective surgery or an emergency operation. Classification is used to help communication between the obstetric, midwifery and anaesthetic team for discussion of the most appropriate method of anaesthesia. The decision whether to perform general anesthesia or regional anesthesia (spinal or epidural anaesthetic) is important and is based on many indications, including how urgent the delivery needs to be as well as the medical and obstetric history of the woman. Regional anaesthetic is almost always safer for the woman and the baby but sometimes general anaesthetic is safer for one or both, and the classification of urgency of the delivery is an important issue affecting this decision. | Caesarean section | Wikipedia | 499 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
A planned caesarean (or elective/scheduled caesarean), arranged ahead of time, is most commonly arranged for medical indications which have developed before or during the pregnancy, and ideally after 39 weeks of gestation. In the UK, this is classified as a 'grade 4' section (delivery timed to suit the mother or hospital staff) or as a 'grade 3' section (no maternal or fetal compromise but early delivery needed).
Emergency caesarean sections are performed in pregnancies in which a vaginal delivery was planned initially, but an indication for caesarean delivery has since developed. In the UK they are further classified as grade 2 (delivery required within 90 minutes of the decision but no immediate threat to the life of the woman or the fetus) or grade 1 (delivery required within 30 minutes of the decision: immediate threat to the life of the mother or the baby or both.)
Elective caesarean sections may be performed on the basis of an obstetrical or medical indication, or because of a medically non-indicated maternal request. Among women in the United Kingdom, Sweden and Australia, about 7% preferred caesarean section as a method of delivery. In cases without medical indications the American Congress of Obstetricians and Gynecologists and the UK Royal College of Obstetricians and Gynaecologists recommend a planned vaginal delivery. The National Institute for Health and Care Excellence recommends that if after a woman has been provided information on the risk of a planned caesarean section and she still insists on the procedure it should be provided. If provided this should be done at 39 weeks of gestation or later. There is no evidence that ECS can reduce mother-to-child hepatitis B and hepatitis C virus transmission.
By characteristics of the mother
Caesarean delivery on maternal request | Caesarean section | Wikipedia | 367 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Caesarean delivery on maternal request (CDMR) is a medically unnecessary caesarean section, where the conduct of a childbirth via a caesarean section is requested by the pregnant patient even though there is not a medical indication to have the surgery. Systematic reviews have found no strong evidence about the impact of caesareans for nonmedical reasons. Recommendations encourage counseling to identify the reasons for the request, addressing anxieties and information, and encouraging vaginal birth. Elective caesareans at 38 weeks in some studies showed increased health complications in the newborn. For this reason ACOG and NICE recommend that elective caesarean sections should not be scheduled before 39 weeks gestation unless there is a medical reason. Planned caesarean sections may be scheduled earlier if there is a medical reason.
After previous caesarean
Mothers who have previously had a caesarean section are more likely to have a caesarean section for future pregnancies than mothers who have never had a caesarean section. There is discussion about the circumstances under which women should have a vaginal birth after a previous caesarean.
Vaginal birth after caesarean (VBAC) is the practice of birthing a baby vaginally after a previous baby has been delivered by caesarean section (surgically). According to the American College of Obstetricians and Gynecologists (ACOG), successful VBAC is associated with decreased maternal morbidity and a decreased risk of complications in future pregnancies. According to the American Pregnancy Association, 90% of women who have undergone caesarean deliveries are candidates for VBAC. Approximately 60–80% of women opting for VBAC will successfully give birth vaginally, which is comparable to the overall vaginal delivery rate in the United States in 2010.
Twins
For otherwise healthy twin pregnancies where both twins are head down a trial of vaginal delivery is recommended at between 37 and 38 weeks. Vaginal delivery in this case does not worsen the outcome for either infant as compared with caesarean section. There is controversy on the best method of delivery where the first twin is head first and the second is not. When the first twin is not head down at the point of labor starting, a caesarean section should be recommended. Although the second twin typically has a higher frequency of problems, it is not known if a planned caesarean section affects this. It is estimated that 75% of twin pregnancies in the United States were delivered by caesarean section in 2008.
Breech birth | Caesarean section | Wikipedia | 510 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
A breech birth is the birth of a baby from a breech presentation, in which the baby exits the pelvis with the buttocks or feet first as opposed to the normal head-first presentation. In breech presentation, fetal heart sounds are heard just above the umbilicus.
Babies are usually born head first. If the baby is in another position the birth may be complicated. In a 'breech presentation', the unborn baby is bottom-down instead of head-down. Babies born bottom-first are more likely to be harmed during a normal (vaginal) birth than those born head-first. For instance, the baby might not get enough oxygen during the birth. Having a planned caesarean may reduce these problems. A review looking at planned caesarean section for singleton breech presentation with planned vaginal birth, concludes that in the short term, births with a planned caesarean were safer for babies than vaginal births. Fewer babies died or were seriously hurt when they were born by caesarean. There was tentative evidence that children who were born by caesarean had more health problems at age two. Caesareans caused some short-term problems for mothers such as more abdominal pain. They also had some benefits, such as less urinary incontinence and less perineal pain.
The bottom-down position presents some hazards to the baby during the process of birth, and the mode of delivery (vaginal versus caesarean) is controversial in the fields of obstetrics and midwifery.
Though vaginal birth is possible for the breech baby, certain fetal and maternal factors influence the safety of vaginal breech birth. The majority of breech babies born in the United States and the UK are delivered by caesarean section as studies have shown increased risks of morbidity and mortality for vaginal breech delivery, and most obstetricians counsel against planned vaginal breech birth for this reason. As a result of reduced numbers of actual vaginal breech deliveries, obstetricians and midwives are at risk of de-skilling in this important skill. All those involved in delivery of obstetric and midwifery care in the UK undergo mandatory training in conducting breech deliveries in the simulation environment (using dummy pelvises and mannequins to allow practice of this important skill) and this training is carried out regularly to keep skills up to date.
Resuscitative hysterotomy | Caesarean section | Wikipedia | 498 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
A resuscitative hysterotomy, also known as a peri-mortem caesarean delivery, is an emergency caesarean delivery carried out where maternal cardiac arrest has occurred, to assist in resuscitation of the mother by removing the aortocaval compression generated by the gravid uterus. Unlike other forms of caesarean section, the welfare of the fetus is a secondary priority only, and the procedure may be performed even prior to the limit of fetal viability if it is judged to be of benefit to the mother.
Other ways, including the surgery technique
There are several types of caesarean section (CS). An important distinction lies in the type of incision (longitudinal or transverse) made on the uterus, apart from the incision on the skin: the vast majority of skin incisions are a transverse suprapubic approach known as a Pfannenstiel incision but there is no way of knowing from the skin scar which way the uterine incision was conducted.
The classical caesarean section involves a longitudinal midline incision on the uterus which allows a larger space to deliver the baby. It is performed at very early gestations where the lower segment of the uterus is unformed as it is safer in this situation for the baby: but it is rarely performed other than at these early gestations, as the operation is more prone to complications than a low transverse uterine incision. Any woman who has had a classical section will be recommended to have an elective repeat section in subsequent pregnancies as the vertical incision is much more likely to rupture in labor than the transverse incision.
The lower uterine segment section is the procedure most commonly used today; it involves a transverse cut just above the edge of the bladder. It results in less blood loss and has fewer early and late complications for the mother, as well as allowing her to consider a vaginal birth in the next pregnancy.
A caesarean hysterectomy consists of a caesarean section followed by the removal of the uterus. This may be done in cases of intractable bleeding or when the placenta cannot be separated from the uterus.
The EXIT procedure is a specialized surgical delivery procedure used to deliver babies who have airway compression. | Caesarean section | Wikipedia | 467 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
The Misgav Ladach method is a modified caesarean section which has been used nearly all over the world since the 1990s. It was described by Michael Stark, the president of the New European Surgical Academy, at the time he was the director of Misgav Ladach, a general hospital in Jerusalem. The method was presented during a FIGO conference in Montréal in 1994 and then distributed by the University of Uppsala, Sweden, in more than 100 countries. This method is based on minimalistic principles. He examined all steps in caesarean sections in use, analyzed them for their necessity and, if found necessary, for their optimal way of performance. For the abdominal incision he used the modified Joel Cohen incision and compared the longitudinal abdominal structures to strings on musical instruments. As blood vessels and muscles have lateral sway, it is possible to stretch rather than cut them. The peritoneum is opened by repeat stretching, no abdominal swabs are used, the uterus is closed in one layer with a big needle to reduce the amount of foreign body as much as possible, the peritoneal layers remain unsutured and the abdomen is closed with two layers only. Women undergoing this operation recover quickly and can look after the newborns soon after surgery. There are many publications showing the advantages over traditional caesarean section methods. There is also an increased risk of abruptio placentae and uterine rupture in subsequent pregnancies for women who underwent this method in prior deliveries.
Since 2015, the World Health Organization has endorsed the Robson classification as a holistic means of comparing childbirth rates between different settings, with a view to allowing more accurate comparison of caesarean section rates.
Technique
Antibiotic prophylaxis is used before an incision. The uterus is incised, and this incision is extended with blunt pressure along a cephalad-caudad axis. The infant is delivered, and the placenta is then removed. The surgeon then makes a decision about uterine exteriorization. Single-layer uterine closure is used when the mother does not want a future pregnancy. When subcutaneous tissue is 2 cm thick or more, surgical suture is used. Discouraged practices include manual cervical dilation, any subcutaneous drain, or supplemental oxygen therapy with intent to prevent infection. | Caesarean section | Wikipedia | 467 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Caesarean section can be performed with single or double layer suturing of the uterine incision. Single layer closure compared with double layer closure has been observed to result in reduced blood loss during the surgery. It is uncertain whether this is the direct effect of the suturing technique or if other factors such as the type and site of abdominal incision contribute to reduced blood loss. Standard procedure includes the closure of the peritoneum. Research questions whether this is needed, with some studies indicating peritoneal closure is associated with longer operative time and hospital stay. The Misgav Ladach method is a surgery technical that may have fewer secondary complications and faster healing, due to the insertion into the muscle.
Anesthesia
Both general and regional anaesthesia (spinal, epidural or combined spinal and epidural anaesthesia) are acceptable for use during caesarean section. Evidence does not show a difference between regional anaesthesia and general anaesthesia with respect to major outcomes in the mother or baby. Regional anaesthesia may be preferred as it allows the mother to be awake and interact immediately with her baby. Compared to general anaesthesia, regional anaesthesia is better at preventing persistent postoperative pain 3 to 8 months after caesarean section. Other advantages of regional anesthesia may include the absence of typical risks of general anesthesia: pulmonary aspiration (which has a relatively high incidence in patients undergoing anesthesia in late pregnancy) of gastric contents and esophageal intubation. One trial found no difference in satisfaction when general anaesthesia was compared with either spinal anaesthesia.
Regional anaesthesia is used in 95% of deliveries, with spinal and combined spinal and epidural anaesthesia being the most commonly used regional techniques in scheduled caesarean section. Regional anaesthesia during caesarean section is different from the analgesia (pain relief) used in labor and vaginal delivery. The pain that is experienced because of surgery is greater than that of labor and therefore requires a more intense nerve block.
General anesthesia may be necessary because of specific risks to mother or child. Patients with heavy, uncontrolled bleeding may not tolerate the hemodynamic effects of regional anesthesia. General anesthesia is also preferred in very urgent cases, such as severe fetal distress, when there is no time to perform a regional anesthesia.
Prevention of complications | Caesarean section | Wikipedia | 472 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Postpartum infection is one of the main causes of maternal death and may account for 10% of maternal deaths globally. A caesarean section greatly increases the risk of infection and associated morbidity, estimated to be between 5 and 20 times as high, and routine use of antibiotic prophylaxis to prevent infections was found by a meta-analysis to substantially reduce the incidence of febrile morbidity. Infection can occur in around 8% of women who have caesareans, largely endometritis, urinary tract infections and wound infections. The use of preventative antibiotics in women undergoing caesarean section decreased wound infection, endometritis, and serious infectious complications by about 65%. Side effects and effect on the baby is unclear.
Women who have caesareans can recognize the signs of fever that indicate the possibility of wound infection. Taking antibiotics before skin incision rather than after cord clamping reduces the risk for the mother, without increasing adverse effects for the baby. Moderate certainty evidence suggest that chlorhexidine gluconate as a skin preparation is slightly more effective in prevention surgical site infections than povidone-iodine but further research is needed.
Some doctors believe that during a caesarean section, mechanical cervical dilation with a finger or forceps will prevent the obstruction of blood and lochia drainage, and thereby benefit the mother by reducing the risk of death. The evidence neither supported nor refuted this practice for reducing postoperative morbidity, pending further large studies.
Hypotension (low blood pressure) is common in women who have spinal anaesthesia; intravenous fluids such as crystalloids, or compressing the legs with bandages, stockings, or inflatable devices may help to reduce the risk of hypotension but the evidence is still uncertain about their effectiveness.
Skin-to-skin contact
The WHO and UNICEF recommend that infants born by Caesarean section should have skin-to-skin contact (SSC) as soon as the mother is alert and responsive. Immediate SSC following a spinal or epidural anesthetic is possible because the mother remains alert; however, after a general anesthetic the father or other family member may provide SSC until the mother is able. | Caesarean section | Wikipedia | 460 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
It is known that during the hours of labor before a vaginal birth a woman's body begins to produce oxytocin which aids in the bonding process, and it is thought that SSC can trigger its production as well. Indeed, women have reported that they felt that SSC had helped them to feel close to and bond with their infant. A review of literature also found that immediate or early SSC increased the likelihood of successful breastfeeding and that newborns were found to cry less and relax quicker when they had SSC with their father as well.
Recovery
It is common for women who undergo caesarean section to have reduced or absent bowel movements for hours to days. During this time, women may experience abdominal cramps, nausea and vomiting. This usually resolves without treatment. Poorly controlled pain following non-emergent caesarean section occurs in between 13% and 78% of women. Following caesarean delivery, complementary and alternative therapies (e.g., acupuncture) may help to relieve pain, though evidence supporting the efficacy of such treatments is extremely limited. Abdominal, wound and back pain can continue for months after a caesarean section. Non-steroidal anti-inflammatory drugs can be helpful. For the first couple of weeks after a caesarean, women should avoid lifting anything heavier than their baby. To minimize pain during breastfeeding, women should experiment with different breastfeeding holds including the football hold and side-lying hold. Women who have had a caesarean are more likely to experience pain that interferes with their usual activities than women who have vaginal births, although by six months there is generally no longer a difference. Pain during sexual intercourse is less likely than after vaginal birth; by six months there is no difference.
There may be a somewhat higher incidence of postnatal depression in the first weeks after childbirth for women who have caesarean sections, but this difference does not persist. Some women who have had caesarean sections, especially emergency caesareans, experience post-traumatic stress disorder.
A woman who undergoes caesarean section has 18.3% chance of chronic surgical pain at three months and 6.8% chance of surgical pain at 12 months. | Caesarean section | Wikipedia | 448 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
In recent meta-analyses, caesarean section has been associated to a lower risk of urinary incontinence and pelvic organ prolapse compared to vaginal delivery. Women who have vaginal births, after a previous caesarean, are more than twice as likely to subsequently have pelvic floor surgery as those who have another caesarean.
Frequency
Global rates of caesarean section are increasing. It doubled from 2003 to 2018 to reach 21%, and is increasing annually by 4%. The trend towards increasing rates is particularly strong in middle and high income countries. In southern Africa, the cesarean rate is less than 5%; while the rate is almost 60% in some parts of Latin America. The Canadian rate was 26% in 2005–2006. Australia has a high caesarean section rate, at 31% in 2007. At one time a rate of 10% to 15% was thought to be ideal; a rate of 19% may result in better outcomes. The World Health Organization officially withdrew its previous recommendation of a 15% C-section rate in June 2010. Their official statement read, "There is no empirical evidence for an optimum percentage. What matters most is that all women who need caesarean sections receive them."
More than 50 nations have rates greater than 27%. Another 45 countries have rates less than 7.5%. There are efforts to both improve access to and reduce the use of C-section. Globally, 1% of all caesarean deliveries are carried out without medical need. Overall, the caesarean section rate was 25.7% for 2004–2008.
There is no significant difference in caesarean rates when comparing midwife continuity care to conventional fragmented care. More emergency caesareans—about 66%—are performed during the day rather than the night.
The rate has risen to 46% in China and to levels of 25% and above in many Asian, European and Latin American countries. In Brazil and Iran the caesarean section rate is greater than 40%. Brazil has one of the highest caesarean section rates in the world, with rates in the public sector of 35–45%, and 80–90% in the private sector.
Europe
Across Europe, there are differences between countries: in Italy the caesarean section rate is 40%, while in the Nordic countries it is 14%. In the United Kingdom, in 2008, the rate was 24%. In Ireland the rate was 26.1% in 2009. | Caesarean section | Wikipedia | 501 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
In Italy, the incidence of caesarean sections is particularly high, although it varies from region to region. In Campania, 60% of 2008 births reportedly occurred via caesarean sections. In the Rome region, the mean incidence is around 44%, but can reach as high as 85% in some private clinics.
United States
In the United States, cesarean deliveries began rising in the 1960s and started becoming routine in the 1960s and 1970s.
In the United States the rate of C-section is around 33%, varying from 23% to 40% depending on the state. One of three women who gave birth in the US delivered by caesarean in 2011. In 2012, close to 23 million C-sections were carried out globally.
With nearly 1.3 million stays, caesarean section was one of the most common procedures performed in U.S. hospitals in 2011. It was the second-most common procedure performed for people ages 18 to 44 years old. Caesarean rates in the U.S. have risen considerably since 1996. The rate has increased in the United States, to 33% of all births in 2012, up from 21% in 1996. In 2010, the caesarean delivery rate was 32.8% of all births (a slight decrease from 2009's high of 32.9% of all births). A study found that in 2011, women covered by private insurance were 11% more likely to have a caesarean section delivery than those covered by Medicaid. The increase in use has not resulted in improved outcomes, resulting in the position that C-sections may be done too frequently. It is believed that the high rate of induced deliveries has also led to the high rate of c-sections because they are twice as likely to lead to one. | Caesarean section | Wikipedia | 357 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Hospitals and doctors make more money from C-section births than vaginal deliveries. Economists have calculated that hospitals may make a few thousand dollars more and doctors a few hundred. It has been found that for-profit hospitals do more c-sections than non-profit hospitals. One study looked at the rate of c-sections done for women who were themselves doctors. It found that there was a 10 percent decrease to the rate of c-sections vs the general population. But if the hospital paid their doctors a flat salary removing the incentive to do the surgical procedures, which take more time, the rate of c-sections done on women who were themselves physicians exceeded that of the procedure done on non-medically knowledgeable mothers, suggesting that some women who actually needed c-sections were not getting them.
Concerned over the rising number of cesarean deliveries and hospital costs, in 2009 Minnesota introduced a blended payment rate for either vaginal or cesarean uncomplicated births (i.e., a similar payment regardless of delivery mode). As a result, the prepolicy cesarean rate of 22.8% dropped 3.24 percentage points. The cost of childbirth hospitalizations in Minnesota dropped by $425.80 at the time the policy was initiated and continued to drop by $95.04 per quarter with no significant effects on maternal morbidity.
The rise of cesarean births in the United States has coincided with counter-movements emphasizing natural childbirth with a lesser degree of medical intervention.
China
The rate of cesarean sections began to sharply increase in China in the 1990s. This increase was driven by the expansion of China's modern hospital infrastructure, and occurred first in urban areas. The rise in cesarean deliveries has also resulted in social critique of the medical establishment over the medical necessity of performing cesarean sections.
History
Historically, caesarean sections performed upon a live woman usually resulted in the death of the mother. It was considered an extreme measure, performed only when the mother was already dead or considered to be beyond help. By way of comparison, see the resuscitative hysterotomy or perimortem caesarean section.
According to the ancient Chinese Records of the Grand Historian, Luzhong (), a sixth-generation descendant of the mythical Yellow Emperor, had six sons, all born by "cutting open the body". The sixth son Jilian founded the House of Mi that ruled the State of Chu (–223 BC). | Caesarean section | Wikipedia | 495 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
The Sanskrit medical treatise Sushruta Samhita, composed in the early 1st millennium CE, mentions post-mortem caesarean sections. The first available non-mythical record of a C-section is the mother of Bindusara (born , ruled 298 – ), the second Mauryan Samrat (emperor) of India, accidentally consumed poison and died when she was close to delivering him. Chanakya, Chandragupta's teacher and adviser, made up his mind that the baby should survive. He cut open the belly of the queen and took out the baby, thus saving the baby's life.
An early account of caesarean section in Iran (Persia) is mentioned in the book of Shahnameh, written around 1000 AD, and relates to the birth of Rostam, the legendary hero of that country. According to the Shahnameh, the Simurgh instructed Zal upon how to perform a caesarean section, thus saving Rudaba and the child Rostam. In Persian literature caesarean section is known as Rostamina ().
In the Irish mythological text the Ulster Cycle, the character Furbaide Ferbend is said to have been born by posthumous caesarean section, after his mother was murdered by his evil aunt Medb.
The Babylonian Talmud, an ancient Jewish religious text, mentions a procedure similar to the caesarean section. The procedure is termed . It also discusses at length the permissibility of performing a C-section on a dying or dead mother. There is also some basis for supposing that Jewish women regularly survived the operation in Roman times (as early as the 2nd century AD).
Pliny the Elder theorized that Julius Caesar's (born 100 BC) name came from an ancestor who was born by caesarean section, but the truth of this is debated (see the discussion of the etymology of Caesar). Some popular misconceptions involve Caesar himself being born from the procedure; which is considered false because the procedure was lethal to mothers in ancient Rome and Caesar's mother Aurelia Cotta lived until he was an adult. The Ancient Roman caesarean section was first performed to remove a baby from the womb of a mother who died during childbirth, a practice sometimes called the Caesarean law.
The Spanish saint Raymond Nonnatus (1204–1240) received his surname—from the Latin ('not born')—because he was born by caesarean section. His mother died while giving birth to him. | Caesarean section | Wikipedia | 509 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
There is some indirect evidence that the first caesarean section that was survived by both the mother and child was performed in Prague in 1337. The mother was Beatrice of Bourbon, the second wife of the King of Bohemia John of Luxembourg. Beatrice gave birth to the king's son Wenceslaus I, later the duke of Luxembourg, Brabant, and Limburg, and who became the half brother of the later King of Bohemia and Holy Roman Emperor, Charles IV.
In an account from the 1580s, Jakob Nufer, a veterinarian in Siegershausen, Switzerland, is supposed to have performed the operation on his wife after a prolonged labour, with her surviving. His wife allegedly bore five more children, including twins, and the baby delivered by caesarean section purportedly lived to the age of 77.
For most of the time since the 16th century, the procedure had a high mortality rate by modern standards. Key steps in reducing mortality were:
Introduction of the transverse incision technique to minimize bleeding by Ferdinand Adolf Kehrer in 1881 is thought to be first modern CS performed.
The introduction of uterine suturing by Max Sänger in 1882
Modification by Hermann Johannes Pfannenstiel in 1900, see Pfannenstiel incision
Extraperitoneal CS and then moving to low transverse incision (Krönig, 1912)
Adherence to principles of asepsis
Anesthesia advances
Blood transfusion
Antibiotics
Indigenous people in the Great Lakes region of Africa, including Rwanda and Uganda, performed caesarean sections which in one account by Robert William Felkin from 1879 resulted in the survival of both mother and child. Banana wine was used, although the site of the incision was then also washed with water and, post operation, covered with a paste made by chewing two different roots. From the well-developed nature of the medical procedures employed he concluded that these procedures had been employed for some time. James Barry was the first European doctor to carry out a successful caesarean in Africa, while posted to Cape Town between 1817 and 1828.
The first successful caesarean section to be performed in the United States took place in Rockingham County, Virginia in 1794. The procedure was performed by Dr. Jesse Bennett on his wife Elizabeth.
Caesarius of Terracina | Caesarean section | Wikipedia | 454 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
The patron saint of caesarean section is Caesarius, a young deacon martyred at Terracina, who has replaced and Christianized the pagan figure of Caesar. The martyr (Saint Cesareo in Italian) is invoked for the success of this surgical procedure, because it was considered the new "Christian Caesar" – as opposed to the "pagan Caesar" – in the Middle Ages it began to be invoked by pregnant women to wish a physiological birth, for the success of the expulsion of the baby from the uterus and, therefore, for their salvation and that of the unborn. The practice continues, in fact the martyr Caesarius is invoked by the future mothers who, due to health problems or that of the baby, must give birth to their child by caesarean section.
Etymology
The origin of the term is not definitively known. Roman Lex Regia (royal law), later the (imperial law), of Numa Pompilius (715–673 BC), required the child of a mother who had died during childbirth to be cut from her womb.
There was a cultural taboo that mothers should not be buried pregnant, that may have reflected a way of saving some fetuses. Roman practice required a living mother to be in her tenth month of pregnancy before resorting to the procedure, reflecting the knowledge that she could not survive the delivery. | Caesarean section | Wikipedia | 275 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Speculations that the Roman dictator Julius Caesar was born by the method now known as C-section are false. Although caesarean sections were performed in Roman times, no classical source records a mother surviving such a delivery, while Caesar's mother lived for years after his birth. As late as the 12th century, scholar and physician Maimonides expresses doubt over the possibility of a woman's surviving this procedure and again becoming pregnant. The term has also been explained as deriving from the verb caedere, 'to cut', with children delivered this way referred to as . Pliny the Elder refers to a certain Julius Caesar (an ancestor of the famous Roman statesman) as , 'cut from the womb' giving this as an explanation for the cognomen Caesar which was then carried by his descendants. Nonetheless, the false etymology has been widely repeated until recently. For example, the first (1888) and second (1989) editions of the Oxford English Dictionary say that caesarean birth "was done in the case of Julius Cæsar". More recent dictionaries are more diffident: the online edition of the OED (2021) mentions "the traditional belief that Julius Cæsar was delivered this way", and Merriam-Webster's Collegiate Dictionary (2003) says "from the legendary association of such a delivery with the Roman cognomen Caesar".
The word Caesar, meaning either Julius Caesar or an emperor in general, is also borrowed or calqued in the name of the procedure in many other languages in Europe and beyond.
Finally, the Roman praenomen (given name) Caeso was said to be given to children who were born via C-section. While this was probably just folk etymology made popular by Pliny the Elder, it was well known by the time the term came into common use.
Spelling
The term caesarean is spelled in various accepted ways, as discussed at Wiktionary. The Medical Subject Headings (MeSH) of the United States National Library of Medicine (NLM) uses cesarean section, while some other American medical works, e.g. Saunders Comprehensive Veterinary Dictionary, use caesarean, as do most British works. The online versions of the US-published Merriam-Webster Dictionary and American Heritage Dictionary list cesarean first and other spellings as "variants".
Society and culture | Caesarean section | Wikipedia | 478 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Court cases
In re A.C., 573 A.2d 1235 (1990), was a District of Columbia Court of Appeals case. It was the first American appellate court case decided against a forced Caesarean section, although the decision was issued after the fatal procedure was performed. Physicians performed a Caesarean section upon patient Angela Carder (née Stoner) without informed consent in an unsuccessful attempt to save the life of her baby. The case stands as a landmark in United States case law establishing the rights of informed consent and bodily integrity for pregnant women.
In Illinois, In re Baby Boy Doe, 632 N.E.2d 326 (Ill. App. Ct. 1994) was a court case holding that courts may not balance whatever rights a fetus may have against the rights of a competent woman, whose choice to refuse medical treatment as invasive as a Cesarean section must be honored even if the choice may be harmful to the fetus. | Caesarean section | Wikipedia | 192 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Pemberton v. Tallahassee Memorial Regional Center, 66 F. Supp. 2d 1247 (N.D. Fla. 1999), is a case in the United States regarding reproductive rights. Pemberton had a previous Caesarean section (vertical incision), and with her second child attempted to have a VBAC (vaginal birth after c-section). When a doctor she had approached about a related issue at the Tallahassee Memorial Regional Center found out, he and the hospital sued to force her to get a c-section. The court held that the rights of the fetus at or near birth outweighed the rights of Pemberton to determine her own medical care. She was physically forced to stop laboring, and taken to the hospital, where a c-section was performed. Her suit against the hospital was dismissed. The court held that a cesarean section at the end of a full-term pregnancy was here deemed to be medically necessary by doctors to avoid a substantial risk that the fetus would die during delivery due to uterine rupture, a risk of 4–6% according to the hospital's doctors and 2% according to Pemberton's doctors. Furthermore, the court held that a state's interest in preserving the life of an unborn child outweighed the mother's constitutional interest of bodily integrity. The court held that Roe v. Wade was not applicable, because bearing an unwanted child is a greater intrusion on the mother's constitutional interests than undergoing a cesarean section to deliver a child that the mother affirmatively desires to deliver. The court further distinguished In re A.C. by stating that it left open the possibility that a non-consenting patient's interest would yield to a more compelling countervailing interest in an "extremely rare and truly exceptional case." The court then held this case to be such.
Presence of father
In many hospitals, the mother's partner is encouraged to attend the surgery to support her and share the experience. While traditionally there has been an opaque surgical drape obstructing the parents' view, some patients and doctors are opting for a "gentle C-section" using a clear drape, allowing the parents to watch the delivery and see their infant immediately. | Caesarean section | Wikipedia | 469 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
Special cases
In Judaism, there is a dispute among the poskim (Rabbinic authorities) as to whether the first-born son from a caesarean section has the laws of a bechor. Traditionally, a male child delivered by caesarean is not eligible for the Pidyon HaBen dedication ritual.
In rare cases, caesarean sections can be used to remove a dead fetus; otherwise, the woman has to labour and deliver a baby known to be a stillbirth. A late-term abortion using caesarean section procedures is termed a hysterotomy abortion and is very rarely performed.
The mother may perform a caesarean section on herself; there have been successful cases, such as Inés Ramírez Pérez of Mexico who, on 5 March 2000, took this action. She survived, as did her son, Orlando Ruiz Ramírez.
In 2024, a female western lowland gorilla had a successful cesarean section after zoo veterinarians diagnosed her with pre-eclampsia. The premature gorilla infant survived, as a result of similar methods used with human infants. | Caesarean section | Wikipedia | 219 | 46924 | https://en.wikipedia.org/wiki/Caesarean%20section | Biology and health sciences | Surgery | Health |
The Koch snowflake (also known as the Koch curve, Koch star, or Koch island) is a fractal curve and one of the earliest fractals to have been described. It is based on the Koch curve, which appeared in a 1904 paper titled "On a Continuous Curve Without Tangents, Constructible from Elementary Geometry" by the Swedish mathematician Helge von Koch.
The Koch snowflake can be built up iteratively, in a sequence of stages. The first stage is an equilateral triangle, and each successive stage is formed by adding outward bends to each side of the previous stage, making smaller equilateral triangles. The areas enclosed by the successive stages in the construction of the snowflake converge to times the area of the original triangle, while the perimeters of the successive stages increase without bound. Consequently, the snowflake encloses a finite area, but has an infinite perimeter.
The Koch snowflake has been constructed as an example of a continuous curve where drawing a tangent line to any point is impossible. Unlike the earlier Weierstrass function where the proof was purely analytical, the Koch snowflake was created to be possible to geometrically represent at the time, so that this property could also be seen through "naive intuition".
Origin and history
There is no doubt that the snowflake curve is based on the von Koch curve and its iterative construction. However, the picture of the snowflake does not appear in either the original article published in 1904 nor in the extended 1906 memoir. So one can ask who is the man who constructed the snowflake figure first. An investigation of this question suggests that the snowflake curve is due to the American mathematician Edward Kasner.
Construction
The Koch snowflake can be constructed by starting with an equilateral triangle, then recursively altering each line segment as follows:
divide the line segment into three segments of equal length.
draw an equilateral triangle that has the middle segment from step 1 as its base and points outward.
remove the line segment that is the base of the triangle from step 2.
The first iteration of this process produces the outline of a hexagram.
The Koch snowflake is the limit approached as the above steps are followed indefinitely. The Koch curve originally described by Helge von Koch is constructed using only one of the three sides of the original triangle. In other words, three Koch curves make a Koch snowflake. | Koch snowflake | Wikipedia | 503 | 46959 | https://en.wikipedia.org/wiki/Koch%20snowflake | Mathematics | Other | null |
A Koch curve–based representation of a nominally flat surface can similarly be created by repeatedly segmenting each line in a sawtooth pattern of segments with a given angle.
Properties
Perimeter of the Koch snowflake
Each iteration multiplies the number of sides in the Koch snowflake by four, so the number of sides after iterations is given by:
If the original equilateral triangle has sides of length , the length of each side of the snowflake after iterations is:
an inverse power of three multiple of the original length.
The perimeter of the snowflake after iterations is:
The Koch curve has an infinite length, because the total length of the curve increases by a factor of with each iteration. Each iteration creates four times as many line segments as in the previous iteration, with the length of each one being the length of the segments in the previous stage. Hence, the length of the curve after iterations will be times the original triangle perimeter and is unbounded, as tends to infinity.
Limit of perimeter
As the number of iterations tends to infinity, the limit of the perimeter is:
since .
An -dimensional measure exists, but has not been calculated so far. Only upper and lower bounds have been invented.
Area of the Koch snowflake
In each iteration a new triangle is added on each side of the previous iteration, so the number of new triangles added in iteration is:
The area of each new triangle added in an iteration is of the area of each triangle added in the previous iteration, so the area of each triangle added in iteration is:
where is the area of the original triangle. The total new area added in iteration is therefore:
The total area of the snowflake after iterations is:
Collapsing the geometric sum gives:
Limits of area
The limit of the area is:
since .
Thus, the area of the Koch snowflake is of the area of the original triangle. Expressed in terms of the side length of the original triangle, this is:
Solid of revolution
The volume of the solid of revolution of the Koch snowflake about an axis of symmetry of the initiating equilateral triangle of unit side is
Other properties
The Koch snowflake is self-replicating with six smaller copies surrounding one larger copy at the center. Hence, it is an irrep-7 irrep-tile (see Rep-tile for discussion). | Koch snowflake | Wikipedia | 484 | 46959 | https://en.wikipedia.org/wiki/Koch%20snowflake | Mathematics | Other | null |
The fractal dimension of the Koch curve is . This is greater than that of a line () but less than that of Peano's space-filling curve ().
It is impossible to draw a tangent line to any point of the curve.
Representation as a de Rham curve
The Koch curve arises as a special case of a de Rham curve. The de Rham curves are mappings of Cantor space into the plane, usually arranged so as to form a continuous curve. Every point on a continuous de Rham curve corresponds to a real number in the unit interval. For the Koch curve, the tips of the snowflake correspond to the dyadic rationals: each tip can be uniquely labeled with a distinct dyadic rational.
Tessellation of the plane
It is possible to tessellate the plane by copies of Koch snowflakes in two different sizes. However, such a tessellation is not possible using only snowflakes of one size. Since each Koch snowflake in the tessellation can be subdivided into seven smaller snowflakes of two different sizes, it is also possible to find tessellations that use more than two sizes at once. Koch snowflakes and Koch antisnowflakes of the same size may be used to tile the plane.
Thue–Morse sequence and turtle graphics
A turtle graphic is the curve that is generated if an automaton is programmed with a sequence.
If the Thue–Morse sequence members are used in order to select program states:
If , move ahead by one unit,
If , rotate counterclockwise by an angle of ,
the resulting curve converges to the Koch snowflake.
Representation as Lindenmayer system
The Koch curve can be expressed by the following rewrite system (Lindenmayer system):
Alphabet : F
Constants : +, −
Axiom : F
Production rules : F → F+F--F+F
Here, F means "draw forward", - means "turn right 60°", and + means "turn left 60°".
To create the Koch snowflake, one would use F--F--F (an equilateral triangle) as the axiom.
Variants of the Koch curve
Following von Koch's concept, several variants of the Koch curve were designed, considering right angles (quadratic), other angles (Cesàro), circles and polyhedra and their extensions to higher dimensions (Sphereflake and Kochcube, respectively) | Koch snowflake | Wikipedia | 510 | 46959 | https://en.wikipedia.org/wiki/Koch%20snowflake | Mathematics | Other | null |
Squares can be used to generate similar fractal curves. Starting with a unit square and adding to each side at each iteration a square with dimension one third of the squares in the previous iteration, it can be shown that both the length of the perimeter and the total area are determined by geometric progressions. The progression for the area converges to while the progression for the perimeter diverges to infinity, so as in the case of the Koch snowflake, we have a finite area bounded by an infinite fractal curve. The resulting area fills a square with the same center as the original, but twice the area, and rotated by radians, the perimeter touching but never overlapping itself.
The total area covered at the th iteration is:
while the total length of the perimeter is:
which approaches infinity as increases.
Functionalisation
In addition to the curve, the paper by Helge von Koch that has established the Koch curve shows a variation of the curve as an example of a continuous everywhere yet nowhere differentiable function that was possible to represent geometrically at the time. From the base straight line, represented as AB, the graph can be drawn by recursively applying the following on each line segment:
Divide the line segment (XY) into three parts of equal length, divided by dots C and E.
Draw a line DM, where M is the middle point of CE, and DM is perpendicular to the initial base of AB, having the length of .
Draw the lines CD and DE and erase the lines CE and DM.
Each point of AB can be shown to converge to a single height. If is defined as the distance of that point to the initial base, then as a function is continuous everywhere and differentiable nowhere. | Koch snowflake | Wikipedia | 351 | 46959 | https://en.wikipedia.org/wiki/Koch%20snowflake | Mathematics | Other | null |
A sleep disorder, or somnipathy, is a medical disorder affecting an individual's sleep patterns, sometimes impacting physical, mental, social, and emotional functioning. Polysomnography and actigraphy are tests commonly ordered for diagnosing sleep disorders.
Sleep disorders are broadly classified into dyssomnias, parasomnias, circadian rhythm sleep disorders involving the timing of sleep, and other disorders, including those caused by medical or psychological conditions. When a person struggles to fall asleep or stay asleep without any obvious cause, it is referred to as insomnia, which is the most common sleep disorder. Other sleep disorders include sleep apnea, narcolepsy, hypersomnia (excessive sleepiness at inappropriate times), sleeping sickness (disruption of the sleep cycle due to infection), sleepwalking, and night terrors.
Sleep disruptions can be caused by various issues, including teeth grinding (bruxism) and night terrors. Managing sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on addressing the underlying conditions.
Sleep disorders are common in both children and adults. However, there is a significant lack of awareness about sleep disorders in children, with many cases remaining unidentified. Several common factors involved in the onset of a sleep disorder include increased medication use, age-related changes in circadian rhythms, environmental changes, lifestyle changes, pre-diagnosed physiological problems, or stress. Among the elderly, the risk of developing sleep-disordered breathing, periodic limb movements, restless legs syndrome, REM sleep behavior disorders, insomnia, and circadian rhythm disturbances is especially high.
Causes
A systematic review found that traumatic childhood experiences, such as family conflict or sexual trauma, significantly increase the risk of several sleep disorders in adulthood, including sleep apnea, narcolepsy, and insomnia.
An evidence-based synopsis suggests that idiopathic REM sleep behavior disorder (iRBD) may have a hereditary component. A total of 632 participants, half with iRBD and half without, completed self-report questionnaires. The study results suggest that people with iRBD are more likely to report having a first-degree relative with the same sleep disorder than people of the same age and sex who do not have the disorder. More research is needed to further understand the hereditary nature of sleep disorders. | Sleep disorder | Wikipedia | 481 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
A population susceptible to the development of sleep disorders includes people who have experienced a traumatic brain injury (TBI). Due to the significant research focus on this issue, a systematic review was conducted to synthesize the findings. The results indicate that individuals who have experienced a TBI are most disproportionately at risk for developing narcolepsy, obstructive sleep apnea, excessive daytime sleepiness, and insomnia.
Sleep disorders and neurodegenerative diseases
Neurodegenerative diseases are often associated with sleep disorders, particularly when characterized by the abnormal accumulation of alpha-synuclein, as seen in multiple system atrophy (MSA), Parkinson's disease (PD), and Lewy body disease (LBD). For example, individuals diagnosed with PD frequently experience various sleep issues, such as insomnia (affecting approximately 70% of the PD population), hypersomnia (over 50%), and REM sleep behavior disorder (RBD) (around 40%), which is linked to increased motor symptoms. Moreover, RBD has been identified as a significant precursor for the future development of these neurodegenerative diseases over several years, presenting a promising opportunity for improving treatments.
Neurodegenerative conditions are commonly related to structural brain impairments, which may disrupt sleep and wakefulness, circadian rhythm, and motor or non-motor functioning. Conversely, sleep disturbances are often linked to worsening patients' cognitive functioning, emotional state, and quality of life. Additionally, these abnormal behavioral symptoms can place a significant burden on their relatives and caregivers. The limited research in this area, coupled with increasing life expectancy, highlights the need for a deeper understanding of the relationship between sleep disorders and neurodegenerative diseases. | Sleep disorder | Wikipedia | 367 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Sleep disturbances and Alzheimer's disease
Sleep disturbances have also been observed in Alzheimer's disease (AD), affecting about 45% of its population. When based on caregiver reports, this percentage increases to about 70%. As in the PD population, insomnia and hypersomnia are frequently recognized in AD patients. These disturbances have been associated with the accumulation of beta-amyloid, circadian rhythm sleep disorders (CRSD), and melatonin alteration. Additionally, changes in sleep architecture are observed in AD. Although sleep architecture seems to naturally change with age, its development appears aggravated in AD patients. Slow-wave sleep (SWS) potentially decreases (and is sometimes absent), spindles and the length of time spent in REM sleep are also reduced, while its latency increases. Poor sleep onset in AD has been associated with dream-related hallucinations, increased restlessness, wandering, and agitation related to sundowning—a typical chronobiological phenomenon in the disease.
In Alzheimer's disease, in addition to cognitive decline and memory impairment, there are also significant sleep disturbances with modified sleep architecture. These disturbances may consist of sleep fragmentation, reduced sleep duration, insomnia, increased daytime napping, decreased quantity of some sleep stages, and a growing resemblance between some sleep stages (N1 and N2). More than 65% of people with Alzheimer's disease experience this type of sleep disturbance.
One factor that could explain this change in sleep architecture is a disruption in the circadian rhythm, which regulates sleep. This disruption can lead to sleep disturbances. Some studies show that people with Alzheimer's disease have a delayed circadian rhythm, whereas in normal aging, an advanced circadian rhythm is present.
In addition to these psychological symptoms, there are two main neurological symptoms of Alzheimer's disease. The first is the accumulation of beta-amyloid waste, forming aggregate "plaques". The second is the accumulation of tau protein.
It has been shown that the sleep-wake cycle influences the beta-amyloid burden, a central component found in Alzheimer's disease (AD). As individuals awaken, the production of beta-amyloid protein becomes more consistent compared to its production during sleep. This phenomenon can be explained by two factors. First, metabolic activity is higher during waking hours, resulting in greater secretion of beta-amyloid protein. Second, oxidative stress increases during waking hours, which leads to greater beta-amyloid production. | Sleep disorder | Wikipedia | 507 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
On the other hand, it is during sleep that beta-amyloid residues are degraded to prevent plaque formation. The glymphatic system is responsible for this through the phenomenon of glymphatic clearance. Thus, during wakefulness, the AB burden is greater because the metabolic activity and oxidative stress are higher, and there is no protein degradation by the glymphatic clearance. During sleep, the burden is reduced as there is less metabolic activity and oxidative stress (in addition to the glymphatic clearance that occurs).
Glymphatic clearance occurs during the NREM SWS sleep. This sleep stage decreases in normal aging, resulting in less glymphatic clearance and increased AB burden that will form AB plaques. Therefore, sleep disturbances in individuals with AD will amplify this phenomenon.
The decrease in the quantity and quality of the NREM SWS, as well as the disturbances of sleep will therefore increase the AB plaques. This initially occurs in the hippocampus, which is a brain structure integral in long-term memory formation. Hippocampus cell death occurs, which contributes to diminished memory performance and cognitive decline found in AD.
Although the causal relationship is unclear, the development of AD correlates with the development of prominent sleep disorders. In the same way, sleep disorders exacerbate disease progression, forming a positive feedback relationship. As a result, sleep disturbances are no longer only a symptom of AD; the relationship between sleep disturbances and AD is bidirectional.
At the same time, it has been shown that memory consolidation in long-term memory (which depends on the hippocampus) occurs during NREM sleep. This indicates that a decrease in the NREM sleep will result in less consolidation, resulting in poorer memory performances in hippocampal-dependent long-term memory. This drop in performance is one of the central symptoms of AD.
Recent studies have also linked sleep disturbances, neurogenesis and AD. The subgranular zone and the subventricular zone continued to produce new neurons in adult brains. These new cells are then incorporated into neuronal circuits and the subgranular zone, which is found in the hippocampus. These new cells contribute to learning and memory, playing an essential role in hippocampal-dependent memory. | Sleep disorder | Wikipedia | 482 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
However, recent studies have shown that several factors can interrupt neurogenesis, including stress and prolonged sleep deprivation (more than one day). The sleep disturbances encountered in AD could therefore suppress neurogenesis—and thus impair hippocampal functions. This would contribute to diminished memory performances and the progression of AD, and the progression of AD would aggravate sleep disturbances.
Changes in sleep architecture found in patients with AD occur during the preclinical phase of AD. These changes could be used to detect those most at risk of developing AD. However, this is still only theoretical.
While the exact mechanisms and the causal relationship between sleep disturbances and AD remains unclear, these findings already provide a better understanding and offer possibilities to improve targeting of at-risk populations—and the implementation of treatments to curb the cognitive decline of AD patients.
Sleep disorder symptoms in psychiatric illnesses
Schizophrenia
In individuals with psychiatric illnesses sleep disorders may include a variety of clinical symptoms, including but not limited to: excessive daytime sleepiness, difficulty falling asleep, difficulty staying asleep, nightmares, sleep talking, sleepwalking, and poor sleep quality. Sleep disturbances - insomnia, hypersomnia and delayed sleep-phase disorder - are quite prevalent in severe mental illnesses such as psychotic disorders. In those with schizophrenia, sleep disorders contribute to cognitive deficits in learning and memory. Sleep disturbances often occur before the onset of psychosis.
Sleep deprivation can also produce hallucinations, delusions and depression. A 2019 study investigated the three above-mentioned sleep disturbances in schizophrenia-spectrum (SCZ) and bipolar (BP) disorders in 617 SCZ individuals, 440 BP individuals, and 173 healthy controls (HC). Sleep disturbances were identified using the Inventory for Depressive Symptoms - clinician rated scale (IDS-C). Results suggested that at least one type of sleep disturbance was reported in 78% of the SCZ population, in 69% individuals with BD, and in 39% of healthy controls. The SCZ group reported the most number of sleep disturbances compared to the BD and HC groups; specifically, hypersomnia was more frequent among individuals with SCZ, and delayed sleep phase disorder was three times more common in the SCZ group compared to the BD group. Insomnias were the most frequently reported sleep disturbance across all three groups. | Sleep disorder | Wikipedia | 470 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Bipolar disorder
One of the main behavioral symptoms of bipolar disorder is abnormal sleep. Studies have suggested that 23-78% of individuals with bipolar disorders consistently report symptoms of excessive time spent sleeping, or hypersomnia. The pathogenesis of bipolar disorder, including the higher risk of suicidal ideation, could possibly be linked to circadian rhythm variability, and sleep disturbances are a good predictor of mood swings. The most common sleep-related symptom of bipolar disorder is insomnia, in addition to hypersomnia, nightmares, poor sleep quality, OSA, extreme daytime sleepiness, etc. Moreover, animal models have shown that sleep debt can induce episodes of bipolar mania in laboratory mice, but these models are still limited in their potential to explain bipolar disease in humans with all its multifaceted symptoms, including those related to sleep disturbances.
Major depressive disorder (MDD)
Sleep disturbances (insomnia or hypersomnia) are not a necessary diagnostic criterion—but one of the most frequent symptoms of individuals with major depressive disorder (MDD). Among individuals with MDD, insomnia and hypersomnia have prevalence estimates of 88% and 27%, respectively, whereas individuals with insomnia have a threefold increased risk of developing MDD. Depressed mood and sleep efficiency strongly co-vary, and while sleep regulation problems may precede depressive episodes, such depressive episodes may also precipitate sleep deprivation. Fatigue, as well as sleep disturbances such as irregular and excessive sleepiness, are linked to symptoms of depression. Recent research has even pointed to sleep problems and fatigues as potential driving forces bridging MDD symptoms to those of co-occurring generalized anxiety disorder.
Treatment
Treatments for sleep disorders generally can be grouped into four categories:
Behavioral and psychotherapeutic treatment
Rehabilitation and management
Medication
Other somatic treatment
None of these general approaches are sufficient for all patients with sleep disorders. Rather, the choice of a specific treatment depends on the patient's diagnosis, medical and psychiatric history, and preferences, as well as the expertise of the treating clinician. Often, behavioral/psychotherapeutic and pharmacological approaches may be compatible, and can effectively be combined to maximize therapeutic benefits. | Sleep disorder | Wikipedia | 451 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders should focus on the underlying conditions. Medications and somatic treatments may provide the most rapid symptomatic relief from certain disorders, such as narcolepsy, which is best treated with prescription drugs such as modafinil. Others, such as chronic and primary insomnia, may be more amenable to behavioral interventions—with more durable results.
Chronic sleep disorders in childhood, which affect some 70% of children with developmental or psychological disorders, are under-reported and under-treated. Sleep-phase disruption is also common among adolescents, whose school schedules are often incompatible with their natural circadian rhythm. Effective treatment begins with careful diagnosis using sleep diaries and perhaps sleep studies. Modifications in sleep hygiene may resolve the problem, but medical treatment is often warranted.
Special equipment may be required for treatment of several disorders such as obstructive apnea, circadian rhythm disorders and bruxism. In severe cases, it may be necessary for individuals to accept living with the disorder, however well managed.
Some sleep disorders have been found to compromise glucose metabolism.
Allergy treatment
Histamine plays a role in wakefulness in the brain. An allergic reaction over produces histamine, causing wakefulness and inhibiting sleep. Sleep problems are common in people with allergic rhinitis. A study from the N.I.H. found that sleep is dramatically impaired by allergic symptoms, and that the degree of impairment is related to the severity of those symptoms. Treatment of allergies has also been shown to help sleep apnea.
Acupuncture
A review of the evidence in 2012 concluded that current research is not rigorous enough to make recommendations around the use of acupuncture for insomnia. The pooled results of two trials on acupuncture showed a moderate likelihood that there may be some improvement to sleep quality for individuals with insomnia. This form of treatment for sleep disorders is generally studied in adults, rather than children. Further research would be needed to study the effects of acupuncture on sleep disorders in children. | Sleep disorder | Wikipedia | 430 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Hypnosis
Research suggests that hypnosis may be helpful in alleviating some types and manifestations of sleep disorders in some patients. "Acute and chronic insomnia often respond to relaxation and hypnotherapy approaches, along with sleep hygiene instructions." Hypnotherapy has also helped with nightmares and sleep terrors. There are several reports of successful use of hypnotherapy for parasomnias specifically for head and body rocking, bedwetting and sleepwalking.
Hypnotherapy has been studied in the treatment of sleep disorders in both adults and children.
Music therapy
Although more research should be done to increase the reliability of this method of treatment, research suggests that music therapy can improve sleep quality in acute and chronic sleep disorders. In one particular study, participants (18 years or older) who had experienced acute or chronic sleep disorders were put in a randomly controlled trial, and their sleep efficiency, in the form of overall time asleep, was observed. In order to assess sleep quality, researchers used subjective measures (i.e. questionnaires) and objective measures (i.e. polysomnography). The results of the study suggest that music therapy did improve sleep quality in subjects with acute or chronic sleep disorders, though only when tested subjectively. Although these results are not fully conclusive and more research should be conducted, it still provides evidence that music therapy can be an effective treatment for sleep disorders.
In another study specifically looking to help people with insomnia, similar results were seen. The participants that listened to music experienced better sleep quality than those who did not listen to music. Listening to slower pace music before bed can help decrease the heart rate, making it easier to transition into sleep. Studies have indicated that music helps induce a state of relaxation that shifts an individual's internal clock towards the sleep cycle. This is said to have an effect on children and adults with various cases of sleep disorders. Music is most effective before bed once the brain has been conditioned to it, helping to achieve sleep much faster. | Sleep disorder | Wikipedia | 421 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Melatonin
Research suggests that melatonin is useful in helping people fall asleep faster (decreased sleep latency), stay asleep longer, and experience improved sleep quality. To test this, a study was conducted that compared subjects who had taken melatonin to subjects with primary sleep disorders who had taken a placebo. Researchers assessed sleep onset latency, total minutes slept, and overall sleep quality in the melatonin and placebo groups to note the differences. In the end, researchers found that melatonin decreased sleep onset latency and increased total sleep time but had an insignificant and inconclusive impact on the quality of sleep compared to the placebo group.
Sleep medicine
Due to rapidly increasing knowledge and understanding of sleep in the 20th century, including the discovery of REM sleep in the 1950s and circadian rhythm disorders in the 70s and 80s, the medical importance of sleep was recognized. By the 1970s in the US, clinics and laboratories devoted to the study of sleep and sleep disorders had been founded, and a need for standards arose. The medical community began paying more attention to primary sleep disorders, such as sleep apnea, as well as the role and quality of sleep in other conditions.
Specialists in sleep medicine were originally and continue to be certified by the American Board of Sleep Medicine. Those passing the Sleep Medicine Specialty Exam received the designation "diplomate of the ABSM". Sleep medicine is now a recognized subspecialty within internal medicine, family medicine, pediatrics, otolaryngology, psychiatry and neurology in the United States. Certification in Sleep medicine shows that the specialist:
Competence in sleep medicine requires an understanding of a myriad of very diverse disorders. Many of which present with similar symptoms such as excessive daytime sleepiness, which, in the absence of volitional sleep deprivation, "is almost inevitably caused by an identifiable and treatable sleep disorder", such as sleep apnea, narcolepsy, idiopathic hypersomnia, Kleine–Levin syndrome, menstrual-related hypersomnia, idiopathic recurrent stupor, or circadian rhythm disturbances. Another common complaint is insomnia, a set of symptoms which can have a great many different causes, physical and mental. Management in the varying situations differs greatly and cannot be undertaken without a correct diagnosis. | Sleep disorder | Wikipedia | 468 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Sleep dentistry (bruxism, snoring and sleep apnea), while not recognized as one of the nine dental specialties, qualifies for board-certification by the American Board of Dental Sleep Medicine (ABDSM). The qualified dentists collaborate with sleep physicians at accredited sleep centers, and can provide oral appliance therapy and upper airway surgery to treat or manage sleep-related breathing disorders. The resulting diplomate status is recognized by the American Academy of Sleep Medicine (AASM), and these dentists are organized in the Academy of Dental Sleep Medicine (USA).
Occupational therapy is an area of medicine that can also address a diagnosis of sleep disorder, as rest and sleep is listed in the Occupational Therapy Practice Framework (OTPF) as its own occupation of daily living. Rest and sleep are described as restorative in order to support engagement in other occupational therapy occupations. In the OTPF, the occupation of rest and sleep is broken down into rest, sleep preparation, and sleep participation. Occupational therapists have been shown to help improve restorative sleep through the use of assistive devices/equipment, cognitive behavioral therapy for Insomnia, therapeutic activities, and lifestyle interventions.
In the UK, knowledge of sleep medicine and possibilities for diagnosis and treatment seem to lag. The Imperial College Healthcare shows attention to obstructive sleep apnea syndrome (OSA) and very few other sleep disorders. Some NHS trusts have specialist clinics for respiratory and neurological sleep medicine.
Epidemiology
Children and young adults
According to one meta-analysis of sleep disorders in children, confusional arousals and sleepwalking are the two most common sleep disorders among children. An estimated 17.3% of kids between 3 and 13 years old experience confusional arousals. About 17% of children sleepwalk, with the disorder being more common among boys than girls, the peak ages of sleepwalking are from 8 to 12 years old.
A different systematic review offers a high range of prevalence rates of sleep bruxism for children. Parasomnias like sleepwalking and talking typically occur during the first part of an individual's sleep cycle, the first slow wave of sleep During the first slow wave of sleep period of the sleep cycle the mind and body slow down causing one to feel drowsy and relaxed. At this stage it is the easiest to wake up, therefore many children do not remember what happened during this time. | Sleep disorder | Wikipedia | 493 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Nightmares are also considered a parasomnia among children, who typically remember what took place during the nightmare. However, nightmares only occur during the last stage of sleep - Rapid Eye Movement (REM) sleep. REM is the deepest stage of sleep, it is named for the host of neurological and physiological responses an individual can display during this period of the sleep cycle which are similar to being awake.
Between 15.29% and 38.6% of preschoolers grind their teeth at least one night a week. All but one of the included studies reports decreasing bruxist prevalence as age increased, as well as a higher prevalence among boys than girls.
Another systematic review noted 7-16% of young adults have delayed sleep phase disorder. This disorder reaches peak prevalence when people are in their 20s. Between 20 and 26% of adolescents report a sleep onset latency of greater than 30 minutes. Also, 7-36% have difficulty initiating sleep. Asian teens tend to have a higher prevalence of all of these adverse sleep outcomes—than their North American and European counterparts.
By adulthood, parasomnias can normally be resolved due to a person's growth; however, 4% of people have recurring symptoms.
Effects of Untreated Sleep Disorders
Children and young adults who do not get enough sleep due to sleep disorders also have many other health problems such as obesity and physical problems where it could interfere with everyday life. It is recommended that children and young adults stick to the hours of sleep recommended by the CDC, as it helps increase mental health, physical health, and more.
Insomnia
Insomnia is a prevalent form of sleep deprivation. Individuals with insomnia may have problems falling asleep, staying asleep, or a combination of both resulting in hyposomnia - i.e. insufficient quantity and poor quality of sleep.
Combining results from 17 studies on insomnia in China, a pooled prevalence of 15.0% is reported for the country. This result is consistent among other East Asian countries; however, this is considerably lower than a series of Western countries (50.5% in Poland, 37.2% in France and Italy, 27.1% in USA). Men and women residing in China experience insomnia at similar rates. | Sleep disorder | Wikipedia | 457 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
A separate meta-analysis focusing on this sleeping disorder in the elderly mentions that those with more than one physical or psychiatric malady experience it at a 60% higher rate than those with one condition or less. It also notes a higher prevalence of insomnia in women over the age of 50 than their male counterparts.
A study that was resulted from a collaboration between Massachusetts General Hospital and Merck describes the development of an algorithm to identify patients with sleep disorders using electronic medical records. The algorithm that incorporated a combination of structured and unstructured variables identified more than 36,000 individuals with physician-documented insomnia.
Insomnia can start off at the basic level but about 40% of people who struggle with insomnia have worse symptoms. There are treatments that can help with insomnia and that includes medication, planning out a sleep schedule, limiting oneself from caffeine intake, and cognitive behavioral therapy.
Obstructive sleep apnea
Obstructive sleep apnea (OSA) affects around 4% of men and 2% of women in the United States. In general, this disorder is more prevalent among men. However, this difference tends to diminish with age. Women experience the highest risk for OSA during pregnancy, and tend to report experiencing depression and insomnia in conjunction with obstructive sleep apnea.
In a meta-analysis of the various Asian countries, India and China present the highest prevalence of the disorder. Specifically, about 13.7% of the Indian population and 7% of Hong Kong's population is estimated to have OSA. The two groups in the study experience daytime OSA symptoms such as difficulties concentrating, mood swings, or high blood pressure, at similar rates (prevalence of 3.5% and 3.57%, respectively). | Sleep disorder | Wikipedia | 364 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Obesity and Sleep Apnea
The worldwide incidence of obstructive sleep apnea (OSA) is on the rise, largely due to the increasing prevalence of obesity in society. In individuals who are obese, excess fat deposits in the upper respiratory tract can lead to breathing difficulties during sleep, giving rise to OSA. There is a strong connection between obesity and OSA, making it essential to screen obese individuals for OSA and related disorders. Moreover, both obesity and OSA patients are at higher risk of developing metabolic syndrome. Implementing dietary control in obese individuals can have a positive impact on sleep problems and can help alleviate associated issues such as depression, anxiety, and insomnia. Obesity can influence the disturbance in sleep patterns resulting in OSA. Obesity is a risk factor for OSA because it can affect the upper respiratory system by accumulating fat deposition around the muscles surrounding the lungs. Additionally, OSA can irritate the obesity by prolonging sleepiness throughout the day leading to reduces physical activity and an inactive lifestyle.
Sleep paralysis
A systematic review states 7.6% of the general population experiences sleep paralysis at least once in their lifetime. Its prevalence among men is 15.9%, while 18.9% of women experience it.
When considering specific populations, 28.3% of students and 31.9% of psychiatric patients have experienced this phenomenon at least once in their lifetime. Of those psychiatric patients, 34.6% have panic disorder. Sleep paralysis in students is slightly more prevalent for those of Asian descent (39.9%) than other ethnicities (Hispanic: 34.5%, African descent: 31.4%, Caucasian 30.8%).
Restless legs syndrome
According to one meta-analysis, the average prevalence rate for North America, and Western Europe is estimated to be 14.5±8.0%. Specifically in the United States, the prevalence of restless legs syndrome is estimated to be between 5% and 15.7% when using strict diagnostic criteria. RLS is over 35% more prevalent in American women than their male counterparts. Restless Leg Syndrome (RLS) is a sensorimotor disorder characterized by discomfort in the lower limbs. Typically, symptoms worsen in the evening, improve with movement, and exacerbate when at rest. | Sleep disorder | Wikipedia | 467 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
List of conditions
There are a numerous sleep disorders. The following list includes some of them:
Bruxism, involuntary grinding or clenching of the teeth while sleeping
Catathrenia, nocturnal groaning during prolonged exhalation
Delayed sleep phase disorder (DSPD), inability to awaken and fall asleep at socially acceptable times but no problem with sleep maintenance, a disorder of circadian rhythms. Other such disorders are advanced sleep phase disorder (ASPD), non-24-hour sleep–wake disorder (non-24) in the sighted or in the blind, and irregular sleep wake rhythm, all much less common than DSPD, as well as the situational shift work sleep disorder.
Fatal familial insomnia, an extremely rare and universally-fatal prion disease that causes a complete cessation of sleep.
Hypopnea syndrome, abnormally shallow breathing or slow respiratory rate while sleeping
Idiopathic hypersomnia, a primary, neurologic cause of long-sleeping, sharing many similarities with narcolepsy
Insomnia disorder (primary insomnia), chronic difficulty in falling asleep or maintaining sleep when no other cause is found for these symptoms. Insomnia can also be comorbid with or secondary to other disorders.
Kleine–Levin syndrome, a rare disorder characterized by persistent episodic hypersomnia and cognitive or mood changes
Narcolepsy, characterized by excessive daytime sleepiness (EDS) and so-called "sleep attacks", relatively sudden-onset, irresistible urges to sleep, which may interfere with occupational and social commitments. About 70% of those who have narcolepsy also have cataplexy, a sudden weakness in the motor muscles that can result in collapse to the floor while retaining full conscious awareness.
Night terror, Pavor nocturnus, sleep terror disorder, an abrupt awakening from sleep with behavior consistent with terror
Nocturia, a frequent need to get up and urinate at night. It differs from enuresis, or bed-wetting, in which the person does not arouse from sleep, but the bladder nevertheless empties.
Parasomnias, disruptive sleep-related events involving inappropriate actions during sleep, for example sleepwalking, night-terrors and catathrenia. | Sleep disorder | Wikipedia | 463 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
Periodic limb movements in sleep (PLMS), sudden involuntary movement of the arms or legs during sleep. In the absence of other sleep disorders, PLMS may cause sleep disruption and impair sleep quality, leading to periodic limb movement disorder (PLMD).
Other limb movements in sleep, including hypneic jerks and nocturnal myoclonus.
Rapid eye movement sleep behavior disorder (RBD), acting out violent or dramatic dreams while in REM sleep, sometimes injuring bed partner or self (REM sleep disorder or RSD)
Restless legs syndrome (RLS), an irresistible urge to move legs.
Shift work sleep disorder (SWSD), a situational circadian rhythm sleep disorder. (Jet lag was previously included as a situational circadian rhythm sleep disorder, but it does not appear in DSM-5, see Diagnostic and Statistical Manual of Mental Disorders for more).
Sleep apnea, obstructive sleep apnea, obstruction of the airway during sleep, causing lack of sufficient deep sleep, often accompanied by snoring. Other forms of sleep apnea are less common. Obstructive sleep apnea (OSA) is a medical disorder that is caused by repetitive collapse of the upper airway (back of the throat) during sleep. For the purposes of sleep studies, episodes of full upper airway collapse for at least ten seconds are called apneas.
Sleep paralysis, characterized by temporary paralysis of the body shortly before or after sleep. Sleep paralysis may be accompanied by visual, auditory or tactile hallucinations. It is not a disorder unless severe, and is often seen as part of narcolepsy.
Sleepwalking or somnambulism, engaging in activities normally associated with wakefulness (such as eating or dressing), which may include walking, without the conscious knowledge of the subject.
Somniphobia, one cause of sleep deprivation, a dread/ fear of falling asleep or going to bed. Signs of the illness include anxiety and panic attacks before and during attempts to sleep. | Sleep disorder | Wikipedia | 417 | 46966 | https://en.wikipedia.org/wiki/Sleep%20disorder | Biology and health sciences | Mental disorders | Health |
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