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9401
symbols is an important clue to the nature of an unknown script. The Armenian alphabet ( ' or ') is a graphically unique alphabetical writing system that has been used to write the Armenian language. It was introduced by Mesrob Mashdots around 405 AD, an Armenian linguist and ecclesiastical leader, and originally contained 36 letters. Two more letters, օ (o) and ֆ (f), were added in the Middle Ages. During the 1920s orthography reform, a new letter և (capital ԵՎ) was added, which was a ligature before ե+ւ, while the letter Ւ ւ was discarded and reintroduced as part of
Alphabet
[ -0.07243227958679199, 0.5894803404808044, -0.23077090084552765, -0.4725562632083893, -0.3228764832019806, 1.0709788799285889, 0.5910466313362122, -0.04826774448156357, -0.25095850229263306, -0.4781495928764343, -0.0858277976512909, -0.14210984110832214, -0.8122024536132812, 0.0638213455677...
9402
a new letter ՈՒ ու (which was a digraph before). The Armenian word for "alphabet" is "" (), named after the first two letters of the Armenian alphabet Ա այբ ayb and Բ բեն ben. The Armenian script's directionality is horizontal left-to-right, like the Latin and Greek alphabets. Alphabets often come to be associated with a standard ordering of their letters, which can then be used for purposes of collation—namely for the listing of words and other items in what is called "alphabetical order". The basic ordering of the Latin alphabet (A B C D E F G H I
Alphabet
[ -0.15307210385799408, 0.45045894384384155, 0.10739053785800934, -0.503628671169281, -0.3165976405143738, 0.5635986328125, 0.5219415426254272, 0.012752866372466087, -0.48115187883377075, -0.8174532651901245, -0.2513865530490875, -0.009511184878647327, -0.5351922512054443, 0.1355291157960891...
9403
J K L M N O P Q R S T U V W X Y Z), which is derived from the Northwest Semitic "Abgad" order, is well established, although languages using this alphabet have different conventions for their treatment of modified letters (such as the French "é", "à", and "ô") and of certain combinations of letters (multigraphs). In French, these are not considered to be additional letters for the purposes of collation. However, in Icelandic, the accented letters such as "á", "í", and "ö" are considered distinct letters representing different vowel sounds from the sounds represented by their unaccented
Alphabet
[ -0.09488026797771454, 0.2171081006526947, 0.13257992267608643, -0.5419437289237976, -0.13744625449180603, 0.42726466059684753, 0.5698013305664062, 0.19172462821006775, -0.47882142663002014, -0.8796703219413757, -0.15799522399902344, 0.04019581899046898, -0.2611386477947235, -0.147875994443...
9404
counterparts. In Spanish, "ñ" is considered a separate letter, but accented vowels such as "á" and "é" are not. The "ll" and "ch" were also considered single letters, but in 1994 the Real Academia Española changed the collating order so that "ll" is between "lk" and "lm" in the dictionary and "ch" is between "cg" and "ci", and in 2010 the tenth congress of the Association of Spanish Language Academies changed it so they were no longer letters at all. In German, words starting with "sch-" (which spells the German phoneme ) are inserted between words with initial "sca-" and
Alphabet
[ -0.0957297682762146, 0.04251287505030632, 0.2419053167104721, -0.21774479746818542, -0.007018657401204109, 0.32683882117271423, 0.056999024003744125, 0.5524611473083496, -0.18903638422489166, -0.7057331800460815, -0.15963348746299744, 0.10089269280433655, 0.046425752341747284, 0.0332976914...
9405
"sci-" (all incidentally loanwords) instead of appearing after initial "sz", as though it were a single letter—in contrast to several languages such as Albanian, in which "dh-", "ë-", "gj-", "ll-", "rr-", "th-", "xh-" and "zh-" (all representing phonemes and considered separate single letters) would follow the letters "d", "e", "g", "l", "n", "r", "t", "x" and "z" respectively, as well as Hungarian and Welsh. Further, German words with umlaut are collated ignoring the umlaut—contrary to Turkish that adopted the graphemes ö and ü, and where a word like "tüfek", would come after "tuz", in the dictionary. An exception is the
Alphabet
[ -0.1322951763868332, 0.08221735805273056, 0.10735613852739334, -0.35018664598464966, -0.05597889423370361, 0.5276003479957581, 0.42138659954071045, 0.3932853639125824, -0.1628626585006714, -0.7997035384178162, -0.2646898925304413, -0.01880302093923092, -0.32867714762687683, 0.0819732099771...
9406
German telephone directory where umlauts are sorted like "ä" = "ae" since names as "Jäger" appear also with the spelling "Jaeger", and are not distinguished in the spoken language. The Danish and Norwegian alphabets end with "æ"—"ø"—"å", whereas the Swedish and Finnish ones conventionally put "å"—"ä"—"ö" at the end. It is unknown whether the earliest alphabets had a defined sequence. Some alphabets today, such as the Hanuno'o script, are learned one letter at a time, in no particular order, and are not used for collation where a definite order is required. However, a dozen Ugaritic tablets from the fourteenth century
Alphabet
[ -0.3012651205062866, 0.18397660553455353, 0.16240942478179932, -0.3001079261302948, -0.35381922125816345, 0.43875208497047424, 0.6757559776306152, 0.2582733631134033, -0.10737311094999313, -0.6186448931694031, -0.09067881107330322, -0.055907681584358215, -0.14982986450195312, 0.07767796516...
9407
BC preserve the alphabet in two sequences. One, the "ABCDE" order later used in Phoenician, has continued with minor changes in Hebrew, Greek, Armenian, Gothic, Cyrillic, and Latin; the other, "HMĦLQ," was used in southern Arabia and is preserved today in Ethiopic. Both orders have therefore been stable for at least 3000 years. Runic used an unrelated Futhark sequence, which was later simplified. Arabic uses its own sequence, although Arabic retains the traditional abjadi order for numbering. The Brahmic family of alphabets used in India use a unique order based on phonology: The letters are arranged according to how and
Alphabet
[ 0.3677191138267517, 0.3410375416278839, -0.07407376915216446, -0.46434128284454346, -0.3312244117259979, 0.45440682768821716, 0.5198530554771423, 0.13641521334648132, -0.22017528116703033, -0.46757742762565613, -0.19378316402435303, -0.32014793157577515, -0.369228333234787, 0.2599281072616...
9408
where they are produced in the mouth. This organization is used in Southeast Asia, Tibet, Korean hangul, and even Japanese kana, which is not an alphabet. The Phoenician letter names, in which each letter was associated with a word that begins with that sound (acrophony), continue to be used to varying degrees in Samaritan, Aramaic, Syriac, Hebrew, Greek and Arabic. The names were abandoned in Latin, which instead referred to the letters by adding a vowel (usually e) before or after the consonant; the two exceptions were Y and Z, which were borrowed from the Greek alphabet rather than Etruscan,
Alphabet
[ -0.13332204520702362, 0.19200986623764038, -0.33719131350517273, -0.5210989117622375, -0.1343121975660324, 0.6736275553703308, 0.4163123369216919, 0.435317724943161, -0.24077944457530975, -0.8119015097618103, -0.10336357355117798, 0.053027138113975525, -0.25694823265075684, 0.2142036110162...
9409
and were known as "Y Graeca" "Greek Y" (pronounced "I Graeca" "Greek I") and "zeta" (from Greek)—this discrepancy was inherited by many European languages, as in the term "zed" for Z in all forms of English other than American English. Over time names sometimes shifted or were added, as in "double U" for W ("double V" in French), the English name for Y, and American "zee" for Z. Comparing names in English and French gives a clear reflection of the Great Vowel Shift: A, B, C and D are pronounced /eɪ, biː, siː, diː/ in today's English, but in contemporary
Alphabet
[ -0.05359026417136192, -0.1575767546892166, -0.18339863419532776, -0.2231024205684662, -0.15106843411922455, 0.5774502754211426, 0.40961307287216187, 0.4081589877605438, -0.18672652542591095, -0.8427208065986633, 0.04236997291445732, -0.05219437554478645, -0.18590714037418365, 0.35737785696...
9410
French they are /a, be, se, de/. The French names (from which the English names are derived) preserve the qualities of the English vowels from before the Great Vowel Shift. By contrast, the names of F, L, M, N and S (/ɛf, ɛl, ɛm, ɛn, ɛs/) remain the same in both languages, because "short" vowels were largely unaffected by the Shift. In Cyrillic originally the letters were given names based on Slavic words; this was later abandoned as well in favor of a system similar to that used in Latin. When an alphabet is adopted or developed to represent a
Alphabet
[ -0.15346753597259521, 0.09586402773857117, -0.0756484791636467, -0.36680853366851807, -0.04888289421796799, 0.7634987831115723, 0.3460119962692261, 0.472038209438324, -0.42792439460754395, -0.9549283385276794, -0.09090641140937805, 0.10362203419208527, -0.07164989411830902, -0.015810159966...
9411
given language, an orthography generally comes into being, providing rules for the spelling of words in that language. In accordance with the principle on which alphabets are based, these rules will generally map letters of the alphabet to the phonemes (significant sounds) of the spoken language. In a perfectly phonemic orthography there would be a consistent one-to-one correspondence between the letters and the phonemes, so that a writer could predict the spelling of a word given its pronunciation, and a speaker would always know the pronunciation of a word given its spelling, and vice versa. However this ideal is not
Alphabet
[ 0.015119112096726894, 0.16213783621788025, 0.008793594315648079, -0.21178176999092102, 0.12495092302560806, 0.2771354913711548, 0.501419186592102, 0.1320466548204422, -0.06794378906488419, -1.2057874202728271, -0.1788523644208908, 0.12985751032829285, -0.025844614952802658, -0.142418846487...
9412
usually achieved in practice; some languages (such as Spanish and Finnish) come close to it, while others (such as English) deviate from it to a much larger degree. The pronunciation of a language often evolves independently of its writing system, and writing systems have been borrowed for languages they were not designed for, so the degree to which letters of an alphabet correspond to phonemes of a language varies greatly from one language to another and even within a single language. Languages may fail to achieve a one-to-one correspondence between letters and sounds in any of several ways: National languages
Alphabet
[ 0.08169084042310715, 0.0752018615603447, -0.14777562022209167, -0.07157880812883377, 0.12191633880138397, 0.21595853567123413, 0.7933446764945984, 0.29915690422058105, -0.18140648305416107, -0.9761417508125305, -0.20584367215633392, 0.050098393112421036, -0.17587754130363464, -0.0709585174...
9413
sometimes elect to address the problem of dialects by simply associating the alphabet with the national standard. Some national languages like Finnish, Turkish, Russian, Serbo-Croatian (Serbian, Croatian and Bosnian) and Bulgarian have a very regular spelling system with a nearly one-to-one correspondence between letters and phonemes. Strictly speaking, these national languages lack a word corresponding to the verb "to spell" (meaning to split a word into its letters), the closest match being a verb meaning to split a word into its syllables. Similarly, the Italian verb corresponding to 'spell (out)', "compitare", is unknown to many Italians because spelling is usually
Alphabet
[ 0.14145874977111816, 0.07843510806560516, -0.12656718492507935, -0.3240852952003479, -0.24367032945156097, 0.322238028049469, 0.5450268983840942, 0.1963680386543274, -0.3942544460296631, -0.7262471914291382, -0.10706594586372375, -0.12956567108631134, -0.41448262333869934, 0.02171162329614...
9414
trivial, as Italian spelling is highly phonemic. In standard Spanish, one can tell the pronunciation of a word from its spelling, but not vice versa, as certain phonemes can be represented in more than one way, but a given letter is consistently pronounced. French, with its silent letters and its heavy use of nasal vowels and elision, may seem to lack much correspondence between spelling and pronunciation, but its rules on pronunciation, though complex, are actually consistent and predictable with a fair degree of accuracy. At the other extreme are languages such as English, where the pronunciations of many words
Alphabet
[ -0.05600569024682045, -0.08106759190559387, -0.14686740934848785, -0.0859166830778122, 0.03886880353093147, 0.19878104329109192, 0.37901824712753296, 0.4289216697216034, -0.2896919250488281, -0.9935113787651062, -0.07000695914030075, 0.2002153992652893, -0.10873765498399734, -0.17017118632...
9415
simply have to be memorized as they do not correspond to the spelling in a consistent way. For English, this is partly because the Great Vowel Shift occurred after the orthography was established, and because English has acquired a large number of loanwords at different times, retaining their original spelling at varying levels. Even English has general, albeit complex, rules that predict pronunciation from spelling, and these rules are successful most of the time; rules to predict spelling from the pronunciation have a higher failure rate. Sometimes, countries have the written language undergo a spelling reform to realign the writing
Alphabet
[ -0.02543136663734913, 0.12672464549541473, -0.13256488740444183, -0.19653990864753723, 0.09429498761892319, 0.056494567543268204, 0.5646292567253113, 0.27818775177001953, -0.18802045285701752, -0.9127249717712402, -0.1299818903207779, -0.01840232126414776, -0.19733846187591553, 0.038603764...
9416
with the contemporary spoken language. These can range from simple spelling changes and word forms to switching the entire writing system itself, as when Turkey switched from the Arabic alphabet to a Latin-based Turkish alphabet. The standard system of symbols used by linguists to represent sounds in any language, independently of orthography, is called the International Phonetic Alphabet. Alphabet An alphabet is a standard set of letters (basic written symbols or graphemes) that represent the phonemes (basic significant sounds) of any spoken language it is used to write. This is in contrast to other types of writing systems, such as
Alphabet
[ 0.2640922963619232, 0.29130131006240845, -0.022315528243780136, -0.35198429226875305, 0.0194674264639616, 0.2614251971244812, 0.4810149371623993, 0.11412414908409119, -0.06470708549022675, -0.9534475803375244, -0.35197028517723083, 0.004827824421226978, -0.2744618058204651, 0.0359452553093...
9417
Atomic number The atomic number or proton number (symbol "Z") of a chemical element is the number of protons found in the nucleus of an atom. It is identical to the charge number of the nucleus. The atomic number uniquely identifies a chemical element. In an uncharged atom, the atomic number is also equal to the number of electrons. The sum of the atomic number "Z" and the number of neutrons, "N", gives the mass number "A" of an atom. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes)
"Atomic number"
[ 0.15634870529174805, 0.3940888047218323, -0.15793199837207794, 0.04615592211484909, -0.25192418694496155, -0.04906383901834488, 0.07714783400297165, -0.2752344310283661, 0.0678512379527092, -0.21145425736904144, -0.19492165744304657, -0.1561996042728424, -0.4193313717842102, 0.816748738288...
9418
and the mass defect of nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in unified atomic mass units (making a quantity called the "relative isotopic mass"), is within 1% of the whole number "A". Atoms with the same atomic number "Z" but different neutron numbers "N", and hence different atomic masses, are known as isotopes. A little more than three-quarters of naturally occurring elements exist as a mixture of isotopes (see monoisotopic elements), and the average isotopic mass of an isotopic mixture for an element (called the relative atomic mass)
"Atomic number"
[ 0.23309682309627533, 0.43780285120010376, -0.21020625531673431, 0.028772879391908646, -0.26944905519485474, -0.16928744316101074, 0.32442453503608704, 0.02080114744603634, 0.052068840712308884, -0.34834733605384827, -0.2885608971118927, -0.2079387903213501, -0.30468833446502686, 0.70855504...
9419
in a defined environment on Earth, determines the element's standard atomic weight. Historically, it was these atomic weights of elements (in comparison to hydrogen) that were the quantities measurable by chemists in the 19th century. The conventional symbol "Z" comes from the German word meaning "number", which, before the modern synthesis of ideas from chemistry and physics, merely denoted an element's numerical place in the periodic table, whose order is approximately, but not completely, consistent with the order of the elements by atomic weights. Only after 1915, with the suggestion and evidence that this "Z" number was also the nuclear
"Atomic number"
[ 0.2811359167098999, 0.2885410487651825, -0.25399643182754517, 0.21565327048301697, -0.15071982145309448, -0.11333425343036652, 0.22312331199645996, -0.04527006298303604, 0.013592815957963467, -0.1502283215522766, -0.11512409895658493, -0.06635725498199463, -0.038543809205293655, 0.93168842...
9420
charge and a physical characteristic of atoms, did the word (and its English equivalent "atomic number") come into common use in this context. Loosely speaking, the existence or construction of a periodic table of elements creates an ordering of the elements, and so they can be numbered in order. Dmitri Mendeleev claimed that he arranged his first periodic tables (first published on March 6th, 1869) in order of atomic weight ("Atomgewicht"). However, in consideration of the elements' observed chemical properties, he changed the order slightly and placed tellurium (atomic weight 127.6) ahead of iodine (atomic weight 126.9). This placement is
"Atomic number"
[ 0.013198423199355602, 0.30959928035736084, -0.18863515555858612, 0.021807022392749786, -0.22715891897678375, 0.2787879407405853, 0.008242459036409855, -0.3057011365890503, -0.22072267532348633, -0.10502234101295471, 0.00690448097884655, -0.26627039909362793, -0.3901480436325073, 0.93353915...
9421
consistent with the modern practice of ordering the elements by proton number, "Z", but that number was not known or suspected at the time. A simple numbering based on periodic table position was never entirely satisfactory, however. Besides the case of iodine and tellurium, later several other pairs of elements (such as argon and potassium, cobalt and nickel) were known to have nearly identical or reversed atomic weights, thus requiring their placement in the periodic table to be determined by their chemical properties. However the gradual identification of more and more chemically similar lanthanide elements, whose atomic number was not
"Atomic number"
[ 0.3821614384651184, 0.37204059958457947, -0.1125698983669281, 0.06607641279697418, -0.40399324893951416, -0.0092024439945817, 0.13055981695652008, -0.1283358931541443, -0.10133127868175507, -0.1625698357820511, -0.007619832642376423, -0.2636009752750397, -0.5178581476211548, 0.995885670185...
9422
obvious, led to inconsistency and uncertainty in the periodic numbering of elements at least from lutetium (element 71) onward (hafnium was not known at this time). In 1911, Ernest Rutherford gave a model of the atom in which a central core held most of the atom's mass and a positive charge which, in units of the electron's charge, was to be approximately equal to half of the atom's atomic weight, expressed in numbers of hydrogen atoms. This central charge would thus be approximately half the atomic weight (though it was almost 25% different from the atomic number of gold ,
"Atomic number"
[ 0.028481123968958855, 0.31622791290283203, -0.09955938905477524, 0.062441252171993256, -0.3394124209880829, 0.10968048870563507, -0.049831002950668335, -0.28544744849205017, -0.23602059483528137, 0.05105413496494293, 0.019541960209608078, -0.23628312349319458, -0.3111122250556946, 1.025289...
9423
), the single element from which Rutherford made his guess). Nevertheless, in spite of Rutherford's estimation that gold had a central charge of about 100 (but was element on the periodic table), a month after Rutherford's paper appeared, Antonius van den Broek first formally suggested that the central charge and number of electrons in an atom was "exactly" equal to its place in the periodic table (also known as element number, atomic number, and symbolized "Z"). This proved eventually to be the case. The experimental position improved dramatically after research by Henry Moseley in 1913. Moseley, after discussions with Bohr
"Atomic number"
[ 0.05554567649960518, 0.28077712655067444, -0.005632973276078701, 0.02152128703892231, -0.35556289553642273, 0.15364015102386475, 0.04513150826096535, -0.5626237392425537, -0.06022404506802559, 0.06356566399335861, 0.018336722627282143, 0.029657140374183655, -0.4432920217514038, 0.928705930...
9424
who was at the same lab (and who had used Van den Broek's hypothesis in his Bohr model of the atom), decided to test Van den Broek's and Bohr's hypothesis directly, by seeing if spectral lines emitted from excited atoms fitted the Bohr theory's postulation that the frequency of the spectral lines be proportional to the square of "Z". To do this, Moseley measured the wavelengths of the innermost photon transitions (K and L lines) produced by the elements from aluminum ("Z" = 13) to gold ("Z" = 79) used as a series of movable anodic targets inside an x-ray
"Atomic number"
[ 0.4214812219142914, 0.03310197964310646, -0.11164049804210663, 0.04637206345796585, -0.3793606162071228, 0.04332701861858368, -0.1336018145084381, -0.4971054494380951, -0.18680837750434875, -0.14240576326847076, -0.02178102917969227, 0.11114397644996643, -0.38133129477500916, 0.86154514551...
9425
tube. The square root of the frequency of these photons increased from one target to the next in an arithmetic progression. This led to the conclusion (Moseley's law) that the atomic number does closely correspond (with an offset of one unit for K-lines, in Moseley's work) to the calculated electric charge of the nucleus, i.e. the element number "Z". Among other things, Moseley demonstrated that the lanthanide series (from lanthanum to lutetium inclusive) must have 15 members—no fewer and no more—which was far from obvious from the chemistry at that time. After Moseley's death in 1915, the atomic numbers of
"Atomic number"
[ 0.460971862077713, 0.28930217027664185, 0.0371037982404232, 0.048743490129709244, -0.34186503291130066, 0.07896725833415985, 0.06479859352111816, -0.4509389400482178, -0.29104816913604736, 0.040389906615018845, -0.1122865229845047, -0.13215044140815735, -0.5838791728019714, 1.2107093334197...
9426
all known elements from hydrogen to uranium ("Z" = 92) were examined by his method. There were seven elements (with "Z" < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and 91. From 1918 to 1947, all seven of these missing elements were discovered. By this time the first four transuranium elements had also been discovered, so that the periodic table was complete with no gaps as far as curium ("Z" = 96). In 1915 the reason for nuclear charge being quantized in units of "Z", which
"Atomic number"
[ 0.4162653088569641, 0.272794246673584, -0.33026108145713806, 0.19156230986118317, -0.2841688394546509, 0.039151113480329514, 0.21486550569534302, -0.045663006603717804, -0.13910269737243652, 0.37470725178718567, 0.09343697875738144, 0.053212013095617294, -0.423825204372406, 1.0836329460144...
9427
were now recognized to be the same as the element number, was not understood. An old idea called Prout's hypothesis had postulated that the elements were all made of residues (or "protyles") of the lightest element hydrogen, which in the Bohr-Rutherford model had a single electron and a nuclear charge of one. However, as early as 1907 Rutherford and Thomas Royds had shown that alpha particles, which had a charge of +2, were the nuclei of helium atoms, which had a mass four times that of hydrogen, not two times. If Prout's hypothesis were true, something had to be neutralizing
"Atomic number"
[ 0.14071446657180786, 0.36236444115638733, -0.12245748937129974, -0.038822125643491745, -0.4631057381629944, -0.1969989538192749, 0.15212540328502655, -0.4695355296134949, -0.10870026797056198, 0.022449148818850517, 0.013321400620043278, -0.3231327533721924, -0.6112663149833679, 0.705664157...
9428
some of the charge of the hydrogen nuclei present in the nuclei of heavier atoms. In 1917 Rutherford succeeded in generating hydrogen nuclei from a nuclear reaction between alpha particles and nitrogen gas, and believed he had proven Prout's law. He called the new heavy nuclear particles protons in 1920 (alternate names being proutons and protyles). It had been immediately apparent from the work of Moseley that the nuclei of heavy atoms have more than twice as much mass as would be expected from their being made of hydrogen nuclei, and thus there was required a hypothesis for the neutralization
"Atomic number"
[ -0.019647402688860893, 0.18295036256313324, -0.023423464968800545, -0.191199392080307, -0.4712368845939636, 0.008067101240158081, 0.04133424907922745, -0.31066974997520447, -0.178517684340477, 0.07756482809782028, -0.17933432757854462, -0.25852516293525696, -0.3954203724861145, 0.830248415...
9429
of the extra protons presumed present in all heavy nuclei. A helium nucleus was presumed to be composed of four protons plus two "nuclear electrons" (electrons bound inside the nucleus) to cancel two of the charges. At the other end of the periodic table, a nucleus of gold with a mass 197 times that of hydrogen, was thought to contain 118 nuclear electrons in the nucleus to give it a residual charge of + 79, consistent with its atomic number. All consideration of nuclear electrons ended with James Chadwick's discovery of the neutron in 1932. An atom of gold now
"Atomic number"
[ 0.11737805604934692, 0.45400598645210266, -0.22846440970897675, -0.08200111985206604, -0.2603960633277893, -0.04043860360980034, 0.17423203587532043, -0.409587562084198, -0.26479312777519226, 0.1314181685447693, -0.18852442502975464, -0.10299505293369293, -0.6160985231399536, 0.76638716459...
9430
was seen as containing 118 neutrons rather than 118 nuclear electrons, and its positive charge now was realized to come entirely from a content of 79 protons. After 1932, therefore, an element's atomic number "Z" was also realized to be identical to the proton number of its nuclei. The conventional symbol "Z" possibly comes from the German word (atomic number). However, prior to 1915, the word "Zahl" (simply "number") was used for an element's assigned number in the periodic table. Each element has a specific set of chemical properties as a consequence of the number of electrons present in the
"Atomic number"
[ 0.22721342742443085, 0.3504451513290405, -0.11331743746995926, 0.1728486716747284, -0.2873801589012146, -0.04179837927222252, 0.14292871952056885, -0.2414570301771164, -0.06876756995916367, -0.008096418343484402, -0.24960340559482574, -0.1194687932729721, -0.2870136797428131, 0.93114036321...
9431
neutral atom, which is "Z" (the atomic number). The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element's electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. Hence, it is the atomic number alone that determines the chemical properties of an element; and it is for this reason that an element can be defined as consisting of "any" mixture of atoms with a given atomic number. The quest for new elements is usually described using atomic numbers. As of 2010, all elements with
"Atomic number"
[ 0.3089462220668793, 0.49984288215637207, -0.025213507935404778, -0.19466441869735718, 0.025935012847185135, -0.1995549201965332, 0.050979405641555786, -0.49269038438796997, 0.12847502529621124, -0.29403042793273926, -0.2628017067909241, 0.0810966044664383, -0.5255643129348755, 0.6260695457...
9432
atomic numbers 1 to 118 have been observed. Synthesis of new elements is accomplished by bombarding target atoms of heavy elements with ions, such that the sum of the atomic numbers of the target and ion elements equals the atomic number of the element being created. In general, the half-life becomes shorter as atomic number increases, though an "island of stability" may exist for undiscovered isotopes with certain numbers of protons and neutrons. Atomic number The atomic number or proton number (symbol "Z") of a chemical element is the number of protons found in the nucleus of an atom. It
"Atomic number"
[ 0.26085665822029114, 0.3329969644546509, -0.2153732031583786, 0.03139635547995567, -0.11528435349464417, -0.20939187705516815, 0.2679700255393982, -0.18247611820697784, 0.006524794269353151, -0.15398800373077393, -0.2326262891292572, -0.07263968139886856, -0.26963210105895996, 0.7437989115...
9433
Anatomy Anatomy (Greek anatomē, "dissection") is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is generated over immediate (embryology) and long (evolution) timescales. Anatomy and physiology, which study (respectively) the structure and function of organisms and their parts, make a natural pair of
Anatomy
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9434
related disciplines, and they are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine. The discipline of anatomy is divided into macroscopic and microscopic anatomy. Macroscopic anatomy, or gross anatomy, is the examination of an animal's body parts using unaided eyesight. Gross anatomy also includes the branch of superficial anatomy. Microscopic anatomy involves the use of optical instruments in the study of the tissues of various structures, known as histology, and also in the study of cells. The history of anatomy is characterized by a progressive understanding of the functions of the
Anatomy
[ 0.7488653659820557, 0.06885272264480591, -0.11407218873500824, 0.150396928191185, 0.07961006462574005, 0.5845215916633606, 0.3433564305305481, 0.22911109030246735, -0.02147224172949791, -1.1213114261627197, -0.13565269112586975, 0.8111198544502258, 0.12572742998600006, 0.2324724942445755, ...
9435
organs and structures of the human body. Methods have also improved dramatically, advancing from the examination of animals by dissection of carcasses and cadavers (corpses) to 20th century medical imaging techniques including X-ray, ultrasound, and magnetic resonance imaging. Derived from the Greek "anatomē" "dissection" (from "anatémnō" "I cut up, cut open" from ἀνά "aná" "up", and τέμνω "témnō" "I cut"), anatomy is the scientific study of the structure of organisms including their systems, organs and tissues. It includes the appearance and position of the various parts, the materials from which they are composed, their locations and their relationships with other
Anatomy
[ 0.6209034323692322, 0.1266859620809555, -0.6111186146736145, 0.08137627691030502, -0.06826569139957428, 0.7694841027259827, 0.3717706501483917, 0.20375950634479523, -0.09952493011951447, -0.991467297077179, -0.0600847564637661, 0.4605884552001953, 0.17165660858154297, 0.3312673568725586, ...
9436
parts. Anatomy is quite distinct from physiology and biochemistry, which deal respectively with the functions of those parts and the chemical processes involved. For example, an anatomist is concerned with the shape, size, position, structure, blood supply and innervation of an organ such as the liver; while a physiologist is interested in the production of bile, the role of the liver in nutrition and the regulation of bodily functions. The discipline of anatomy can be subdivided into a number of branches including gross or macroscopic anatomy and microscopic anatomy. Gross anatomy is the study of structures large enough to be
Anatomy
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9437
seen with the naked eye, and also includes superficial anatomy or surface anatomy, the study by sight of the external body features. Microscopic anatomy is the study of structures on a microscopic scale, along with histology (the study of tissues), and embryology (the study of an organism in its immature condition). Anatomy can be studied using both invasive and non-invasive methods with the goal of obtaining information about the structure and organization of organs and systems. Methods used include dissection, in which a body is opened and its organs studied, and endoscopy, in which a video camera-equipped instrument is inserted
Anatomy
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9438
through a small incision in the body wall and used to explore the internal organs and other structures. Angiography using X-rays or magnetic resonance angiography are methods to visualize blood vessels. The term "anatomy" is commonly taken to refer to human anatomy. However, substantially the same structures and tissues are found throughout the rest of the animal kingdom and the term also includes the anatomy of other animals. The term "zootomy" is also sometimes used to specifically refer to non-human animals. The structure and tissues of plants are of a dissimilar nature and they are studied in plant anatomy. The
Anatomy
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9439
kingdom Animalia contains multicellular organisms that are heterotrophic and motile (although some have secondarily adopted a sessile lifestyle). Most animals have bodies differentiated into separate tissues and these animals are also known as eumetazoans. They have an internal digestive chamber, with one or two openings; the gametes are produced in multicellular sex organs, and the zygotes include a blastula stage in their embryonic development. Metazoans do not include the sponges, which have undifferentiated cells. Unlike plant cells, animal cells have neither a cell wall nor chloroplasts. Vacuoles, when present, are more in number and much smaller than those in the
Anatomy
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9440
plant cell. The body tissues are composed of numerous types of cell, including those found in muscles, nerves and skin. Each typically has a cell membrane formed of phospholipids, cytoplasm and a nucleus. All of the different cells of an animal are derived from the embryonic germ layers. Those simpler invertebrates which are formed from two germ layers of ectoderm and endoderm are called diploblastic and the more developed animals whose structures and organs are formed from three germ layers are called triploblastic. All of a triploblastic animal's tissues and organs are derived from the three germ layers of the
Anatomy
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9441
embryo, the ectoderm, mesoderm and endoderm. Animal tissues can be grouped into four basic types: connective, epithelial, muscle and nervous tissue. Connective tissues are fibrous and made up of cells scattered among inorganic material called the extracellular matrix. Connective tissue gives shape to organs and holds them in place. The main types are loose connective tissue, adipose tissue, fibrous connective tissue, cartilage and bone. The extracellular matrix contains proteins, the chief and most abundant of which is collagen. Collagen plays a major part in organizing and maintaining tissues. The matrix can be modified to form a skeleton to support or
Anatomy
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9442
protect the body. An exoskeleton is a thickened, rigid cuticle which is stiffened by mineralization, as in crustaceans or by the cross-linking of its proteins as in insects. An endoskeleton is internal and present in all developed animals, as well as in many of those less developed. Epithelial tissue is composed of closely packed cells, bound to each other by cell adhesion molecules, with little intercellular space. Epithelial cells can be squamous (flat), cuboidal or columnar and rest on a basal lamina, the upper layer of the basement membrane, the lower layer is the reticular lamina lying next to the
Anatomy
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9443
connective tissue in the extracellular matrix secreted by the epithelial cells. There are many different types of epithelium, modified to suit a particular function. In the respiratory tract there is a type of ciliated epithelial lining; in the small intestine there are microvilli on the epithelial lining and in the large intestine there are intestinal villi. Skin consists of an outer layer of keratinized stratified squamous epithelium that covers the exterior of the vertebrate body. Keratinocytes make up to 95% of the cells in the skin. The epithelial cells on the external surface of the body typically secrete an extracellular
Anatomy
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9444
matrix in the form of a cuticle. In simple animals this may just be a coat of glycoproteins. In more advanced animals, many glands are formed of epithelial cells. Muscle cells (myocytes) form the active contractile tissue of the body. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle is formed of contractile filaments and is separated into three main types; smooth muscle, skeletal muscle and cardiac muscle. Smooth muscle has no striations when examined microscopically. It contracts slowly but maintains contractibility over a wide range of stretch lengths. It is found
Anatomy
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9445
in such organs as sea anemone tentacles and the body wall of sea cucumbers. Skeletal muscle contracts rapidly but has a limited range of extension. It is found in the movement of appendages and jaws. Obliquely striated muscle is intermediate between the other two. The filaments are staggered and this is the type of muscle found in earthworms that can extend slowly or make rapid contractions. In higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets. Smooth muscle is found in the walls of the uterus, bladder, intestines, stomach,
Anatomy
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9446
oesophagus, respiratory airways, and blood vessels. Cardiac muscle is found only in the heart, allowing it to contract and pump blood round the body. Nervous tissue is composed of many nerve cells known as neurons which transmit information. In some slow-moving radially symmetrical marine animals such as ctenophores and cnidarians (including sea anemones and jellyfish), the nerves form a nerve net, but in most animals they are organized longitudinally into bundles. In simple animals, receptor neurons in the body wall cause a local reaction to a stimulus. In more complex animals, specialized receptor cells such as chemoreceptors and photoreceptors are
Anatomy
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9447
found in groups and send messages along neural networks to other parts of the organism. Neurons can be connected together in ganglia. In higher animals, specialized receptors are the basis of sense organs and there is a central nervous system (brain and spinal cord) and a peripheral nervous system. The latter consists of sensory nerves that transmit information from sense organs and motor nerves that influence target organs. The peripheral nervous system is divided into the somatic nervous system which conveys sensation and controls voluntary muscle, and the autonomic nervous system which involuntarily controls smooth muscle, certain glands and internal
Anatomy
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9448
organs, including the stomach. All vertebrates have a similar basic body plan and at some point in their lives, mostly in the embryonic stage, share the major chordate characteristics; a stiffening rod, the notochord; a dorsal hollow tube of nervous material, the neural tube; pharyngeal arches; and a tail posterior to the anus. The spinal cord is protected by the vertebral column and is above the notochord and the gastrointestinal tract is below it. Nervous tissue is derived from the ectoderm, connective tissues are derived from mesoderm, and gut is derived from the endoderm. At the posterior end is a
Anatomy
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9449
tail which continues the spinal cord and vertebrae but not the gut. The mouth is found at the anterior end of the animal, and the anus at the base of the tail. The defining characteristic of a vertebrate is the vertebral column, formed in the development of the segmented series of vertebrae. In most vertebrates the notochord becomes the nucleus pulposus of the intervertebral discs. However, a few vertebrates, such as the sturgeon and the coelacanth retain the notochord into adulthood. Jawed vertebrates are typified by paired appendages, fins or legs, which may be secondarily lost. The limbs of vertebrates
Anatomy
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9450
are considered to be homologous because the same underlying skeletal structure was inherited from their last common ancestor. This is one of the arguments put forward by Charles Darwin to support his theory of evolution. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in cartilaginous fish, or bone in bony fish. The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The
Anatomy
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9451
ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays, which with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. The heart has two chambers and pumps the blood through the respiratory surfaces of the gills and on round the body in a single circulatory loop. The eyes are adapted for seeing underwater and have only local vision. There
Anatomy
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9452
is an inner ear but no external or middle ear. Low frequency vibrations are detected by the lateral line system of sense organs that run along the length of the sides of fish, and these respond to nearby movements and to changes in water pressure. Sharks and rays are basal fish with numerous primitive anatomical features similar to those of ancient fish, including skeletons composed of cartilage. Their bodies tend to be dorso-ventrally flattened, they usually have five pairs of gill slits and a large mouth set on the underside of the head. The dermis is covered with separate dermal
Anatomy
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9453
placoid scales. They have a cloaca into which the urinary and genital passages open, but not a swim bladder. Cartilaginous fish produce a small number of large, yolky eggs. Some species are ovoviviparous and the young develop internally but others are oviparous and the larvae develop externally in egg cases. The bony fish lineage shows more derived anatomical traits, often with major evolutionary changes from the features of ancient fish. They have a bony skeleton, are generally laterally flattened, have five pairs of gills protected by an operculum, and a mouth at or near the tip of the snout. The
Anatomy
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9454
dermis is covered with overlapping scales. Bony fish have a swim bladder which helps them maintain a constant depth in the water column, but not a cloaca. They mostly spawn a large number of small eggs with little yolk which they broadcast into the water column. Amphibians are a class of animals comprising frogs, salamanders and caecilians. They are tetrapods, but the caecilians and a few species of salamander have either no limbs or their limbs are much reduced in size. Their main bones are hollow and lightweight and are fully ossified and the vertebrae interlock with each other and
Anatomy
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9455
have articular processes. Their ribs are usually short and may be fused to the vertebrae. Their skulls are mostly broad and short, and are often incompletely ossified. Their skin contains little keratin and lacks scales, but contains many mucous glands and in some species, poison glands. The hearts of amphibians have three chambers, two atria and one ventricle. They have a urinary bladder and nitrogenous waste products are excreted primarily as urea. Amphibians breathe by means of buccal pumping, a pump action in which air is first drawn into the buccopharyngeal region through the nostrils. These are then closed and
Anatomy
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9456
the air is forced into the lungs by contraction of the throat. They supplement this with gas exchange through the skin which needs to be kept moist. In frogs the pelvic girdle is robust and the hind legs are much longer and stronger than the forelimbs. The feet have four or five digits and the toes are often webbed for swimming or have suction pads for climbing. Frogs have large eyes and no tail. Salamanders resemble lizards in appearance; their short legs project sideways, the belly is close to or in contact with the ground and they have a long
Anatomy
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9457
tail. Caecilians superficially resemble earthworms and are limbless. They burrow by means of zones of muscle contractions which move along the body and they swim by undulating their body from side to side. Reptiles are a class of animals comprising turtles, tuataras, lizards, snakes and crocodiles. They are tetrapods, but the snakes and a few species of lizard either have no limbs or their limbs are much reduced in size. Their bones are better ossified and their skeletons stronger than those of amphibians. The teeth are conical and mostly uniform in size. The surface cells of the epidermis are modified
Anatomy
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9458
into horny scales which create a waterproof layer. Reptiles are unable to use their skin for respiration as do amphibians and have a more efficient respiratory system drawing air into their lungs by expanding their chest walls. The heart resembles that of the amphibian but there is a septum which more completely separates the oxygenated and deoxygenated bloodstreams. The reproductive system has evolved for internal fertilization, with a copulatory organ present in most species. The eggs are surrounded by amniotic membranes which prevents them from drying out and are laid on land, or develop internally in some species. The bladder
Anatomy
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9459
is small as nitrogenous waste is excreted as uric acid. Turtles are notable for their protective shells. They have an inflexible trunk encased in a horny carapace above and a plastron below. These are formed from bony plates embedded in the dermis which are overlain by horny ones and are partially fused with the ribs and spine. The neck is long and flexible and the head and the legs can be drawn back inside the shell. Turtles are vegetarians and the typical reptile teeth have been replaced by sharp, horny plates. In aquatic species, the front legs are modified into
Anatomy
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9460
flippers. Tuataras superficially resemble lizards but the lineages diverged in the Triassic period. There is one living species, "Sphenodon punctatus". The skull has two openings (fenestrae) on either side and the jaw is rigidly attached to the skull. There is one row of teeth in the lower jaw and this fits between the two rows in the upper jaw when the animal chews. The teeth are merely projections of bony material from the jaw and eventually wear down. The brain and heart are more primitive than those of other reptiles, and the lungs have a single chamber and lack bronchi.
Anatomy
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9461
The tuatara has a well-developed parietal eye on its forehead. Lizards have skulls with only one fenestra on each side, the lower bar of bone below the second fenestra having been lost. This results in the jaws being less rigidly attached which allows the mouth to open wider. Lizards are mostly quadrupeds, with the trunk held off the ground by short, sideways-facing legs, but a few species have no limbs and resemble snakes. Lizards have moveable eyelids, eardrums are present and some species have a central parietal eye. Snakes are closely related to lizards, having branched off from a common
Anatomy
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9462
ancestral lineage during the Cretaceous period, and they share many of the same features. The skeleton consists of a skull, a hyoid bone, spine and ribs though a few species retain a vestige of the pelvis and rear limbs in the form of pelvic spurs. The bar under the second fenestra has also been lost and the jaws have extreme flexibility allowing the snake to swallow its prey whole. Snakes lack moveable eyelids, the eyes being covered by transparent "spectacle" scales. They do not have eardrums but can detect ground vibrations through the bones of their skull. Their forked tongues
Anatomy
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9463
are used as organs of taste and smell and some species have sensory pits on their heads enabling them to locate warm-blooded prey. Crocodilians are large, low-slung aquatic reptiles with long snouts and large numbers of teeth. The head and trunk are dorso-ventrally flattened and the tail is laterally compressed. It undulates from side to side to force the animal through the water when swimming. The tough keratinized scales provide body armour and some are fused to the skull. The nostrils, eyes and ears are elevated above the top of the flat head enabling them to remain above the surface
Anatomy
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9464
of the water when the animal is floating. Valves seal the nostrils and ears when it is submerged. Unlike other reptiles, crocodilians have hearts with four chambers allowing complete separation of oxygenated and deoxygenated blood. Birds are tetrapods but though their hind limbs are used for walking or hopping, their front limbs are wings covered with feathers and adapted for flight. Birds are endothermic, have a high metabolic rate, a light skeletal system and powerful muscles. The long bones are thin, hollow and very light. Air sac extensions from the lungs occupy the centre of some bones. The sternum is
Anatomy
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9465
wide and usually has a keel and the caudal vertebrae are fused. There are no teeth and the narrow jaws are adapted into a horn-covered beak. The eyes are relatively large, particularly in nocturnal species such as owls. They face forwards in predators and sideways in ducks. The feathers are outgrowths of the epidermis and are found in localized bands from where they fan out over the skin. Large flight feathers are found on the wings and tail, contour feathers cover the bird's surface and fine down occurs on young birds and under the contour feathers of water birds. The
Anatomy
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9466
only cutaneous gland is the single uropygial gland near the base of the tail. This produces an oily secretion that waterproofs the feathers when the bird preens. There are scales on the legs, feet and claws on the tips of the toes. Mammals are a diverse class of animals, mostly terrestrial but some are aquatic and others have evolved flapping or gliding flight. They mostly have four limbs but some aquatic mammals have no limbs or limbs modified into fins and the forelimbs of bats are modified into wings. The legs of most mammals are situated below the trunk, which
Anatomy
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9467
is held well clear of the ground. The bones of mammals are well ossified and their teeth, which are usually differentiated, are coated in a layer of prismatic enamel. The teeth are shed once (milk teeth) during the animal's lifetime or not at all, as is the case in cetaceans. Mammals have three bones in the middle ear and a cochlea in the inner ear. They are clothed in hair and their skin contains glands which secrete sweat. Some of these glands are specialized as mammary glands, producing milk to feed the young. Mammals breathe with lungs and have a
Anatomy
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9468
muscular diaphragm separating the thorax from the abdomen which helps them draw air into the lungs. The mammalian heart has four chambers and oxygenated and deoxygenated blood are kept entirely separate. Nitrogenous waste is excreted primarily as urea. Mammals are amniotes, and most are viviparous, giving birth to live young. The exception to this are the egg-laying monotremes, the platypus and the echidnas of Australia. Most other mammals have a placenta through which the developing foetus obtains nourishment, but in marsupials, the foetal stage is very short and the immature young is born and finds its way to its mother's
Anatomy
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9469
pouch where it latches on to a nipple and completes its development. Humans have the overall body plan of a mammal. Humans have a head, neck, trunk (which includes the thorax and abdomen), two arms and hands, and two legs and feet. Generally, students of certain biological sciences, paramedics, prosthetists and orthotists, physiotherapists, occupational therapists, nurses, podiatrists, and medical students learn gross anatomy and microscopic anatomy from anatomical models, skeletons, textbooks, diagrams, photographs, lectures and tutorials, and in addition, medical students generally also learn gross anatomy through practical experience of dissection and inspection of cadavers. The study of microscopic anatomy
Anatomy
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9470
(or histology) can be aided by practical experience examining histological preparations (or slides) under a microscope. Human anatomy, physiology and biochemistry are complementary basic medical sciences, which are generally taught to medical students in their first year at medical school. Human anatomy can be taught regionally or systemically; that is, respectively, studying anatomy by bodily regions such as the head and chest, or studying by specific systems, such as the nervous or respiratory systems. The major anatomy textbook, Gray's Anatomy, has been reorganized from a systems format to a regional format, in line with modern teaching methods. A thorough working
Anatomy
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9471
knowledge of anatomy is required by physicians, especially surgeons and doctors working in some diagnostic specialties, such as histopathology and radiology. Academic anatomists are usually employed by universities, medical schools or teaching hospitals. They are often involved in teaching anatomy, and research into certain systems, organs, tissues or cells. Invertebrates constitute a vast array of living organisms ranging from the simplest unicellular eukaryotes such as "Paramecium" to such complex multicellular animals as the octopus, lobster and dragonfly. They constitute about 95% of the animal species. By definition, none of these creatures has a backbone. The cells of single-cell protozoans have
Anatomy
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9472
the same basic structure as those of multicellular animals but some parts are specialized into the equivalent of tissues and organs. Locomotion is often provided by cilia or flagella or may proceed via the advance of pseudopodia, food may be gathered by phagocytosis, energy needs may be supplied by photosynthesis and the cell may be supported by an endoskeleton or an exoskeleton. Some protozoans can form multicellular colonies. Metazoans are multicellular organism, different groups of cells of which have separate functions. The most basic types of metazoan tissues are epithelium and connective tissue, both of which are present in nearly
Anatomy
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9473
all invertebrates. The outer surface of the epidermis is normally formed of epithelial cells and secretes an extracellular matrix which provides support to the organism. An endoskeleton derived from the mesoderm is present in echinoderms, sponges and some cephalopods. Exoskeletons are derived from the epidermis and is composed of chitin in arthropods (insects, spiders, ticks, shrimps, crabs, lobsters). Calcium carbonate constitutes the shells of molluscs, brachiopods and some tube-building polychaete worms and silica forms the exoskeleton of the microscopic diatoms and radiolaria. Other invertebrates may have no rigid structures but the epidermis may secrete a variety of surface coatings such
Anatomy
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9474
as the pinacoderm of sponges, the gelatinous cuticle of cnidarians (polyps, sea anemones, jellyfish) and the collagenous cuticle of annelids. The outer epithelial layer may include cells of several types including sensory cells, gland cells and stinging cells. There may also be protrusions such as microvilli, cilia, bristles, spines and tubercles. Marcello Malpighi, the father of microscopical anatomy, discovered that plants had tubules similar to those he saw in insects like the silk worm. He observed that when a ring-like portion of bark was removed on a trunk a swelling occurred in the tissues above the ring, and he unmistakably
Anatomy
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9475
interpreted this as growth stimulated by food coming down from the leaves, and being captured above the ring. Arthropods comprise the largest phylum in the animal kingdom with over a million known invertebrate species. Insects possess segmented bodies supported by a hard-jointed outer covering, the exoskeleton, made mostly of chitin. The segments of the body are organized into three distinct parts, a head, a thorax and an abdomen. The head typically bears a pair of sensory antennae, a pair of compound eyes, one to three simple eyes (ocelli) and three sets of modified appendages that form the mouthparts. The thorax
Anatomy
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9476
has three pairs of segmented legs, one pair each for the three segments that compose the thorax and one or two pairs of wings. The abdomen is composed of eleven segments, some of which may be fused and houses the digestive, respiratory, excretory and reproductive systems. There is considerable variation between species and many adaptations to the body parts, especially wings, legs, antennae and mouthparts. Spiders a class of arachnids have four pairs of legs; a body of two segments—a cephalothorax and an abdomen. Spiders have no wings and no antennae. They have mouthparts called chelicerae which are often connected
Anatomy
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9477
to venom glands as most spiders are venomous. They have a second pair of appendages called pedipalps attached to the cephalothorax. These have similar segmentation to the legs and function as taste and smell organs. At the end of each male pedipalp is a spoon-shaped cymbium that acts to support the copulatory organ. In 1600 BCE, the Edwin Smith Papyrus, an Ancient Egyptian medical text, described the heart, its vessels, liver, spleen, kidneys, hypothalamus, uterus and bladder, and showed the blood vessels diverging from the heart. The Ebers Papyrus (c. 1550 BCE) features a "treatise on the heart", with vessels
Anatomy
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9478
carrying all the body's fluids to or from every member of the body. Ancient Greek anatomy and physiology underwent great changes and advances throughout the early medieval world. Over time, this medical practice expanded by a continually developing understanding of the functions of organs and structures in the body. Phenomenal anatomical observations of the human body were made, which have contributed towards the understanding of the brain, eye, liver, reproductive organs and the nervous system. The Hellenistic Egyptian city of Alexandria was the stepping-stone for Greek anatomy and physiology. Alexandria not only housed the biggest library for medical records and
Anatomy
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9479
books of the liberal arts in the world during the time of the Greeks, but was also home to many medical practitioners and philosophers. Great patronage of the arts and sciences from the Ptolemy rulers helped raise Alexandria up, further rivalling the cultural and scientific achievements of other Greek states. Some of the most striking advances in early anatomy and physiology took place in Hellenistic Alexandria. Two of the most famous anatomists and physiologists of the third century were Herophilus and Erasistratus. These two physicians helped pioneer human dissection for medical research. They also conducted vivisections on the cadavers of
Anatomy
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9480
condemned criminals, which was considered taboo until the Renaissance – Herophilus was recognized as the first person to perform systematic dissections. Herophilus became known for his anatomical works making impressing contributions to many branches of anatomy and many other aspects of medicine. Some of the works included classifying the system of the pulse, the discovery that human arteries had thicker walls then veins, and that the atria were parts of the heart. Herophilus's knowledge of the human body has provided vital input towards understanding the brain, eye, liver, reproductive organs and nervous system, and characterizing the course of disease. Erasistratus
Anatomy
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9481
accurately described the structure of the brain, including the cavities and membranes, and made a distinction between its cerebrum and cerebellum During his study in Alexandria, Erasistratus was particularly concerned with studies of the circulatory and nervous systems. He was able to distinguish the sensory and the motor nerves in the human body and believed that air entered the lungs and heart, which was then carried throughout the body. His distinction between the arteries and veins – the arteries carrying the air through the body, while the veins carried the blood from the heart was a great anatomical discovery. Erasistratus
Anatomy
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9482
was also responsible for naming and describing the function of the epiglottis and the valves of the heart, including the tricuspid. During the third century, Greek physicians were able to differentiate nerves from blood vessels and tendons and to realize that the nerves convey neural impulses. It was Herophilus who made the point that damage to motor nerves induced paralysis. Herophilus named the meninges and ventricles in the brain, appreciated the division between cerebellum and cerebrum and recognized that the brain was the "seat of intellect" and not a "cooling chamber" as propounded by Aristotle Herophilus is also credited with
Anatomy
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9483
describing the optic, oculomotor, motor division of the trigeminal, facial, vestibulocochlear and hypoglossal nerves. Great feats were made during the third century in both the digestive and reproductive systems. Herophilus was able to discover and describe not only the salivary glands, but the small intestine and liver. He showed that the uterus is a hollow organ and described the ovaries and uterine tubes. He recognized that spermatozoa were produced by the testes and was the first to identify the prostate gland. The anatomy of the muscles and skeleton is described in the "Hippocratic Corpus", an Ancient Greek medical work written
Anatomy
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9484
by unknown authors. Aristotle described vertebrate anatomy based on animal dissection. Praxagoras identified the difference between arteries and veins. Also in the 4th century BCE, Herophilos and Erasistratus produced more accurate anatomical descriptions based on vivisection of criminals in Alexandria during the Ptolemaic dynasty. In the 2nd century, Galen of Pergamum, an anatomist, clinician, writer and philosopher, wrote the final and highly influential anatomy treatise of ancient times. He compiled existing knowledge and studied anatomy through dissection of animals. He was one of the first experimental physiologists through his vivisection experiments on animals. Galen's drawings, based mostly on dog anatomy,
Anatomy
[ 0.3892316520214081, 0.051420100033283234, -0.6163983941078186, 0.2032639980316162, -0.0816059410572052, 1.0392385721206665, 0.31719425320625305, -0.12532182037830353, -0.07752326130867004, -1.0327337980270386, 0.23689384758472443, 0.5531945824623108, -0.10863755643367767, 0.113116338849067...
9485
became effectively the only anatomical textbook for the next thousand years. His work was known to Renaissance doctors only through Islamic Golden Age medicine until it was translated from the Greek some time in the 15th century. Anatomy developed little from classical times until the sixteenth century; as the historian Marie Boas writes, "Progress in anatomy before the sixteenth century is as mysteriously slow as its development after 1500 is startlingly rapid". Between 1275 and 1326, the anatomists Mondino de Luzzi, Alessandro Achillini and Antonio Benivieni at Bologna carried out the first systematic human dissections since ancient times. Mondino's "Anatomy"
Anatomy
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9486
of 1316 was the first textbook in the medieval rediscovery of human anatomy. It describes the body in the order followed in Mondino's dissections, starting with the abdomen, then the thorax, then the head and limbs. It was the standard anatomy textbook for the next century. Leonardo da Vinci (1452–1519) was trained in anatomy by Andrea del Verrocchio. He made use of his anatomical knowledge in his artwork, making many sketches of skeletal structures, muscles and organs of humans and other vertebrates that he dissected. Andreas Vesalius (1514–1564) (Latinized from Andries van Wezel), professor of anatomy at the University of
Anatomy
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9487
Padua, is considered the founder of modern human anatomy. Originally from Brabant, Vesalius published the influential book "De humani corporis fabrica" ("the structure of the human body"), a large format book in seven volumes, in 1543. The accurate and intricately detailed illustrations, often in allegorical poses against Italianate landscapes, are thought to have been made by the artist Jan van Calcar, a pupil of Titian. In England, anatomy was the subject of the first public lectures given in any science; these were given by the Company of Barbers and Surgeons in the 16th century, joined in 1583 by the Lumleian
Anatomy
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9488
lectures in surgery at the Royal College of Physicians. In the United States, medical schools began to be set up towards the end of the 18th century. Classes in anatomy needed a continual stream of cadavers for dissection and these were difficult to obtain. Philadelphia, Baltimore and New York were all renowned for body snatching activity as criminals raided graveyards at night, removing newly buried corpses from their coffins. A similar problem existed in Britain where demand for bodies became so great that grave-raiding and even anatomy murder were practised to obtain cadavers. Some graveyards were in consequence protected with
Anatomy
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9489
watchtowers. The practice was halted in Britain by the Anatomy Act of 1832, while in the United States, similar legislation was enacted after the physician William S. Forbes of Jefferson Medical College was found guilty in 1882 of "complicity with resurrectionists in the despoliation of graves in Lebanon Cemetery". The teaching of anatomy in Britain was transformed by Sir John Struthers, Regius Professor of Anatomy at the University of Aberdeen from 1863 to 1889. He was responsible for setting up the system of three years of "pre-clinical" academic teaching in the sciences underlying medicine, including especially anatomy. This system lasted
Anatomy
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9490
until the reform of medical training in 1993 and 2003. As well as teaching, he collected many vertebrate skeletons for his museum of comparative anatomy, published over 70 research papers, and became famous for his public dissection of the Tay Whale. From 1822 the Royal College of Surgeons regulated the teaching of anatomy in medical schools. Medical museums provided examples in comparative anatomy, and were often used in teaching. Ignaz Semmelweis investigated puerperal fever and he discovered how it was caused. He noticed that the frequently fatal fever occurred more often in mothers examined by medical students than by midwives.
Anatomy
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9491
The students went from the dissecting room to the hospital ward and examined women in childbirth. Semmelweis showed that when the trainees washed their hands in chlorinated lime before each clinical examination, the incidence of puerperal fever among the mothers could be reduced dramatically. Before the modern medical era, the main means for studying the internal structures of the body were dissection of the dead and inspection, palpation and auscultation of the living. It was the advent of microscopy that opened up an understanding of the building blocks that constituted living tissues. Technical advances in the development of achromatic lenses
Anatomy
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9492
increased the resolving power of the microscope and around 1839, Matthias Jakob Schleiden and Theodor Schwann identified that cells were the fundamental unit of organization of all living things. Study of small structures involved passing light through them and the microtome was invented to provide sufficiently thin slices of tissue to examine. Staining techniques using artificial dyes were established to help distinguish between different types of tissue. Advances in the fields of histology and cytology began in the late 19th century along with advances in surgical techniques allowing for the painless and safe removal of biopsy specimens. The invention of
Anatomy
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9493
the electron microscope brought a great advance in resolution power and allowed research into the ultrastructure of cells and the organelles and other structures within them. About the same time, in the 1950s, the use of X-ray diffraction for studying the crystal structures of proteins, nucleic acids and other biological molecules gave rise to a new field of molecular anatomy. Equally important advances have occurred in "non-invasive" techniques for examining the interior structures of the body. X-rays can be passed through the body and used in medical radiography and fluoroscopy to differentiate interior structures that have varying degrees of opaqueness.
Anatomy
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9494
Magnetic resonance imaging, computed tomography, and ultrasound imaging have all enabled examination of internal structures in unprecedented detail to a degree far beyond the imagination of earlier generations. Anatomy Anatomy (Greek anatomē, "dissection") is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is
Anatomy
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9495
Affirming the consequent Affirming the consequent, sometimes called converse error, fallacy of the converse, or confusion of necessity and sufficiency, is a formal fallacy of taking a true conditional statement (e.g., "If the lamp were broken, then the room would be dark,") and invalidly inferring its converse ("The room is dark, so the lamp is broken,") even though the converse may not be true. This arises when a consequent ("the room would be dark") has one or more "other" antecedents (for example, "the lamp is not plugged in" or "the lamp is in working order, but is switched off"). Converse
"Affirming the consequent"
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9496
errors are common in everyday thinking and communication and can result from, among other causes, communication issues, misconceptions about logic, and failure to consider other causes. Affirming the consequent is the action of taking a true statement formula_1 and invalidly concluding its converse formula_2. The name "affirming the consequent" derives from using the consequent, "Q", of formula_1, to conclude the antecedent "P". This illogic can be summarized formally as formula_4 or, alternatively, formula_5. The root cause of such a logic error is sometimes failure to realize that just because "P" is a "possible" condition for "Q", "P" may not be
"Affirming the consequent"
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9497
the "only" condition for "Q", i.e. "Q" may follow from another condition as well. Affirming the consequent can also result from overgeneralizing the experience of many statements "having" true converses. If "P" and "Q" are "equivalent" statements, i.e. formula_6, it "is" possible to infer "P" under the condition "Q". For example, the statements "It is August 13, so it is my birthday" formula_1 and "It is my birthday, so it is August 13" formula_2 are equivalent and both true consequences of the statement "August 13 is my birthday" (an abbreviated form of formula_6). Using one statement to conclude the other
"Affirming the consequent"
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9498
is "not" an example of affirming the consequent, but some person misapply the approach. It may be worth noting that formula_1 "does" imply its contrapositive, formula_11, where formula_12 symbolize the negations of "Q" and "P", respectively. For example, the statement "If the lamp were broken, then the room would be dark," (formula_1) does imply its contrapositive, "The room is "not" dark, so the lamp is "not" broken," (formula_11). Example 1 One way to demonstrate the invalidity of this argument form is with a counterexample with true premises but an obviously false conclusion. For example: Owning Fort Knox is not the
"Affirming the consequent"
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9499
"only" way to be rich. Any number of other ways to be rich exist. However, one can affirm with certainty that "if someone is not rich" ("non-Q"), then "this person does not own Fort Knox" ("non-P"). This is the contrapositive of the first statement, and it must be true if and only if the original statement is true. Example 2 Here is another useful, obviously-fallacious example, but one that does not require familiarity with who Bill Gates is and what Fort Knox is: Here, it is immediately intuitive that any number of other antecedents ("If an animal is a deer...",
"Affirming the consequent"
[ 0.21171346306800842, 0.18500542640686035, 0.17841105163097382, 0.1136486604809761, 0.11813149601221085, -0.2926758825778961, 0.4622868001461029, 0.13965536653995514, -0.03575323894619942, -0.04873603582382202, -0.1972024142742157, 0.6435967683792114, -0.5145281553268433, 0.1551223248243332...
9500
"If an animal is an elephant...", "If an animal is a moose...", etc.) can give rise to the consequent ("then it has four legs"), and that it is preposterous to suppose that having four legs must imply that the animal is a dog and nothing else. This is useful as a teaching example since most people can immediately recognize that the conclusion reached must be wrong (intuitively, a cat cannot be a dog), and that the method by which it was reached must therefore be fallacious. Example 3 Arguments of the same form can sometimes seem superficially convincing, as in
"Affirming the consequent"
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