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Normally, the respiratory centers of the brain maintain a consistent, rhythmic breathing cycle. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high ...	{ "Header 1": "22.7 \| Embryonic Development of the Respiratory System", "Header 3": "[22.6 Modifications in Respiratory Functions](#page-1024-0)", "token_count": 339, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The development of the respiratory system in the fetus begins at about 4 weeks and continues into childhood. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx. At about this same time, an protru...	{ "Header 1": "22.7 \| Embryonic Development of the Respiratory System", "Header 3": "[22.7 Embryonic Development of the Respiratory System](#page-1025-0)", "token_count": 357, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - List and describe the functional anatomy of the organs and accessory organs of the digestive system - Discuss the processes and control of ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation - Discuss the roles of the liver, p...	{ "Header 1": "Introduction", "Header 2": "Chapter Objectives", "token_count": 281, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Identify the organs of the alimentary canal from proximal to distal, and briefly state their function - Identify the accessory digestive organs and briefly state their function - Describe the four fundamental tissue layers of the alimentary canal - Contrast the contr...	{ "Header 1": "23.1 \| Overview of the Digestive System", "token_count": 488, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Throughout its length, the alimentary tract is composed of the same four tissue layers; the details of their structural arrangements vary to fit their specific functions. Starting from the lumen and moving outwards, these layers are the mucosa, submucosa, muscularis, and serosa, which is continuous with the mesentery (...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Histology of the Alimentary Canal", "token_count": 1063, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As soon as food enters the mouth, it is detected by receptors that send impulses along the sensory neurons of cranial nerves. Without these nerves, not only would your food be without taste, but you would also be unable to feel either the food or the structures of your mouth, and you would be unable to avoid biting you...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Nerve Supply", "token_count": 374, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The blood vessels serving the digestive system have two functions. They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen. Lipids are absorbed via lacteals, tiny structures of the lymphatic system. The blood vessels' second function is to supply the organs of...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Blood Supply", "token_count": 277, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which ...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "The Peritoneum", "token_count": 204, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Inflammation of the peritoneum is called peritonitis. Chemical peritonitis can develop any time the wall of the alimentary canal is breached, allowing the contents of the lumen entry into the peritoneal cavity. For example, when an ulcer perforates the stomach wall, gastric juices spill into the peritoneal cavity. Hemo...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Digestive System: Peritonitis", "token_count": 478, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation. The first of these processes, ingestion, refers to the entry of food into the alimentary canal through the mouth. There, the food is chewed and mixed with sal...	{ "Header 1": "23.2 \| Digestive System Processes and Regulation", "Header 3": "Digestive Processes", "token_count": 764, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Age-related changes in the digestive system begin in the mouth and can affect virtually every aspect of the digestive system. Taste buds become less sensitive, so food isn't as appetizing as it once was. A slice of pizza is a challenge, not a treat, when you have lost teeth, your gums are diseased, and your salivary gl...	{ "Header 1": "23.2 \| Digestive System Processes and Regulation", "Header 3": "Digestive System: From Appetite Suppression to Constipation", "token_count": 393, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The walls of the alimentary canal contain a variety of sensors that help regulate digestive functions. These include mechanoreceptors, chemoreceptors, and osmoreceptors, which are capable of detecting mechanical, chemical, and osmotic stimuli, respectively. For example, these receptors can sense when the presence of fo...	{ "Header 1": "23.2 \| Digestive System Processes and Regulation", "Header 3": "Neural Controls", "token_count": 408, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The cheeks, tongue, and palate frame the mouth, which is also called the oral cavity (or buccal cavity). The structures of the mouth are illustrated in [Figure 23.7](#page-1049-0). At the entrance to the mouth are the lips, or labia (singular = labium). Their outer covering is skin, which transitions to a...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Mouth", "token_count": 857, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Perhaps you have heard it said that the tongue is the strongest muscle in the body. Those who stake this claim cite its strength proportionate to its size. Although it is difficult to quantify the relative strength of different muscles, it remains indisputable that the tongue is a workhorse, facilitating ingestion,...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Tongue", "token_count": 783, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Saliva is essentially (95.5 percent) water. The remaining 4.5 percent is a complex mixture of ions, glycoproteins, enzymes, growth factors, and waste products. Perhaps the most important ingredient in salvia from the perspective of digestion is the enzyme salivary amylase, which initiates the breakdown of carbo...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Saliva", "token_count": 405, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Infections of the nasal passages and pharynx can attack any salivary gland. The parotid glands are the usual site of infection with the virus that causes mumps (paramyxovirus). Mumps manifests by enlargement and inflammation of the parotid glands, causing a characteristic swelling between the ears and the jaw. Symptoms...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Parotid Glands: Mumps", "token_count": 207, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The autonomic nervous system regulates salivation (the secretion of saliva). In the absence of food, parasympathetic stimulation keeps saliva flowing at just the right level for comfort as you speak, swallow, sleep, and generally go about life. Over-salivation can occur, for example, if you are stimulated by the sm...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Regulation of Salivation", "token_count": 335, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
During the course of your lifetime, you have two sets of teeth (one set of teeth is a dentition). Your 20 deciduous teeth, or baby teeth, first begin to appear at about 6 months of age. Between approximately age 6 and 12, these teeth are replaced by 32 permanent teeth. Moving from the center of the mouth to...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Types of Teeth", "token_count": 390, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The teeth are secured in the alveolar processes (sockets) of the maxilla and the mandible. Gingivae (commonly called the gums) are soft tissues that line the alveolar processes and surround the necks of the teeth. Teeth are also held in their sockets by a connective tissue called the periodontal ligament. The two...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Anatomy of a Tooth", "token_count": 760, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pharynx (throat) is involved in both digestion and respiration. It receives food and air from the mouth, and air from the nasal cavities. When food enters the pharynx, involuntary muscle contractions close off the air passageways. A short tube of skeletal muscle lined with a mucous membrane, the pharynx runs ...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Pharynx", "token_count": 543, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The upper esophageal sphincter, which is continuous with the inferior pharyngeal constrictor, controls the movement of food from the pharynx into the esophagus. The upper two-thirds of the esophagus consists of both smooth and skeletal muscle fibers, with the latter fading out in the bottom third of the esophagus. ...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Passage of Food through the Esophagus", "token_count": 371, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The mucosa of the esophagus is made up of an epithelial lining that contains non-keratinized, stratified squamous epithelium, with a layer of basal and parabasal cells. This epithelium protects against erosion from food particles. The mucosa's lamina propria contains mucus-secreting glands. The muscularis layer changes...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Histology of the Esophagus", "token_count": 357, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Deglutition is another word for swallowing—the movement of food from the mouth to the stomach. The entire process takes about 4 to 8 seconds for solid or semisolid food, and about 1 second for very soft food and liquids. Although this sounds quick and effortless, deglutition is, in fact, a complex process that invo...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Deglutition", "token_count": 216, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of peristalsis. As in the previous phase, the complex neuromuscular actions are controlled by the medulla oblongata. Peristalsis propels the bolus through the esophagus and toward the stomach. The circular...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Esophageal Phase", "token_count": 306, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Label on a diagram the four main regions of the stomach, its curvatures, and its sphincter - Identify the four main types of secreting cells in gastric glands, and their important products - Explain why the stomach does not digest itself - Describe the mechanical and...	{ "Header 1": "23.4 \| The Stomach", "token_count": 472, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
There are four main regions in the stomach: the cardia, fundus, body, and pylorus ([Figure 23.15](#page-1059-0)). The cardia (or cardiac region) is the point where the esophagus connects to the stomach and through which food passes into the stomach. Located inferior to the diaphragm, above and to the left o...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Structure", "token_count": 376, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The wall of the stomach is made of the same four layers as most of the rest of the alimentary canal, but with adaptations to the mucosa and muscularis for the unique functions of this organ. In addition to the typical circular and longitudinal smooth muscle layers, the muscularis has an inner oblique smooth muscle laye...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Histology", "token_count": 1210, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The secretion of gastric juice is controlled by both nerves and hormones. Stimuli in the brain, stomach, and small intestine activate or inhibit gastric juice production. This is why the three phases of gastric secretion are called the cephalic, gastric, and intestinal phases (Figure 23.17). However, once gastric secre...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Gastric Secretion", "token_count": 608, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As effective as the mucosal barrier is, it is not a "fail-safe" mechanism. Sometimes, gastric juice eats away at the superficial lining of the stomach mucosa, creating erosions, which mostly heal on their own. Deeper and larger erosions are called ulcers. Why does the mucosal barrier break down? A number of factors c...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Ulcers: When the Mucosal Barrier Breaks Down", "token_count": 228, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Within a few moments after food after enters your stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave is a unique type of peristalsis that mixes and softens the food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed b...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Mechanical Digestion", "token_count": 329, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The fundus plays an important role, because it stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Chemical Digestion", "token_count": 397, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Compare and contrast the location and gross anatomy of the small and large intestines - Identify three main adaptations of the small intestine wall that increase its absorptive capacity - Describe the mechanical and chemical digestion of chyme upon its release into t...	{ "Header 1": "23.5 \| The Small and Large Intestines", "token_count": 200, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Chyme released from the stomach enters the small intestine, which is the primary digestive organ in the body. Not only is this where most digestion occurs, it is also where practically all absorption occurs. The longest part of the alimentary canal, the small intestine is about 3.05 meters (10 feet) long in a livin...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "The Small Intestine", "token_count": 232, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The coiled tube of the small intestine is subdivided into three regions. From proximal (at the stomach) to distal, these are the duodenum, jejunum, and ileum ([Figure 23.18](#page-1065-0)). The shortest region is the 25.4-cm (10-in) duodenum, which begins at the pyloric sphincter. Just past the pyloric sphinc...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Structure", "token_count": 668, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The wall of the small intestine is composed of the same four layers typically present in the alimentary system. However, three features of the mucosa and submucosa are unique. These features, which increase the absorptive surface area of the small intestine more than 600-fold, include circular folds, villi, and microvi...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Histology", "token_count": 262, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In addition to the three specialized absorptive features just discussed, the mucosa between the villi is dotted with deep crevices that each lead into a tubular intestinal gland (crypt of Lieberkühn), which is formed by cells that line the crevices (see [Figure 23.19](#page-1066-0)). These produce **intestinal ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Intestinal Glands", "token_count": 545, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The lamina propria of the small intestine mucosa is studded with quite a bit of MALT. In addition to solitary lymphatic nodules, aggregations of intestinal MALT, which are typically referred to as Peyer's patches, are concentrated in the distal ileum, and serve to keep bacteria from entering the bloodstream. Peyer's pa...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Intestinal MALT", "token_count": 235, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The movement of intestinal smooth muscles includes both segmentation and a form of peristalsis called migrating motility complexes. The kind of peristaltic mixing waves seen in the stomach are not observed here. If you could see into the small intestine when it was going through segmentation, it would look as if the ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Mechanical Digestion in the Small Intestine", "token_count": 599, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The digestion of proteins and carbohydrates, which partially occurs in the stomach, is completed in the small intestine with the aid of intestinal and pancreatic juices. Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancre...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Chemical Digestion in the Small Intestine", "token_count": 309, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Lactose intolerance is a condition characterized by indigestion caused by dairy products. It occurs when the absorptive cells of the small intestine do not produce enough lactase, the enzyme that digests the milk sugar lactose. In most mammals, lactose intolerance increases with age. In contrast, some human populations...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Small Intestine: Lactose Intolerance", "token_count": 275, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The first part of the large intestine is the cecum, a sac-like structure that is suspended inferior to the ileocecal valve. It is about 6 cm (2.4 in) long, receives the contents of the ileum, and continues the absorption of water and salts. The appendix (or vermiform appendix) is a winding tube that attaches to...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Cecum", "token_count": 212, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The cecum blends seamlessly with the colon. Upon entering the colon, the food residue first travels up the ascending colon on the right side of the abdomen. At the inferior surface of the liver, the colon bends to form the right colic flexure (hepatic flexure) and becomes the transverse colon. The regio...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Colon", "token_count": 314, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Each year, approximately 140,000 Americans are diagnosed with colorectal cancer, and another 49,000 die from it, making it one of the most deadly malignancies. People with a family history of colorectal cancer are at increased risk. Smoking, excessive alcohol consumption, and a diet high in animal fat and protein also ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Colorectal Cancer", "token_count": 231, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
There are several notable differences between the walls of the large and small intestines ([Figure 23.22](#page-1071-0)). For example, few enzyme-secreting cells are found in the wall of the large intestine, and there are no circular folds or villi. Other than in the anal canal, the mucosa of the colon is simple co...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Histology", "token_count": 292, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Three features are unique to the large intestine: teniae coli, haustra, and epiploic appendages ([Figure 23.23](#page-1072-0)). The teniae coli are three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. Tonic contractions of ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Anatomy", "token_count": 213, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The stratified squamous epithelial mucosa of the anal canal connects to the skin on the outside of the anus. This mucosa varies considerably from that of the rest of the colon to accommodate the high level of abrasion as feces pass through. The anal canal's mucous membrane is organized into longitudinal folds, each cal...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Figure 23.23 Teniae Coli, Haustra, and Epiploic Appendages", "token_count": 234, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Most bacteria that enter the alimentary canal are killed by lysozyme, defensins, HCl, or protein-digesting enzymes. However, trillions of bacteria live within the large intestine and are referred to as the bacterial flora. Most of the more than 700 species of these bacteria are nonpathogenic commensal organisms tha...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Bacterial Flora", "token_count": 281, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the large intestine, mechanical digestion begins when chyme moves from the ileum into the cecum, an activity regulated by the ileocecal sphincter. Right after you eat, peristalsis in the ileum forces chyme into the cecum. When the cecum is distended with chyme, contractions of the ileocecal sphincter strengthen. Onc...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Mechanical Digestion", "token_count": 355, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The small intestine absorbs about 90 percent of the water you ingest (either as liquid or within solid food). The large intestine absorbs most of the remaining water, a process that converts the liquid chyme residue into semisolid feces ("stool"). Feces is composed of undigested food residues, unabsorbed digested s...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Absorption, Feces Formation, and Defecation", "token_count": 607, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - State the main digestive roles of the liver, pancreas, and gallbladder - Identify three main features of liver histology that are critical to its function - Discuss the composition and function of bile - Identify the major types of enzymes and buffers present in panc...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "token_count": 232, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The liver is the largest gland in the body, weighing about three pounds in an adult. It is also one of the most important organs. In addition to being an accessory digestive organ, it plays a number of roles in metabolism and regulation. The liver lies inferior to the diaphragm in the right upper quadrant of the ab...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "The Liver", "token_count": 537, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The liver has three main components: hepatocytes, bile canaliculi, and hepatic sinusoids. A hepatocyte is the liver's main cell type, accounting for around 80 percent of the liver's volume. These cells play a role in a wide variety of secretory, metabolic, and endocrine functions. Plates of hepatocytes called hepat...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Histology", "token_count": 488, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Recall that lipids are hydrophobic, that is, they do not dissolve in water. Thus, before they can be digested in the watery environment of the small intestine, large lipid globules must be broken down into smaller lipid globules, a process called emulsification. Bile is a mixture secreted by the liver to accomplish...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Bile", "token_count": 744, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The soft, oblong, glandular pancreas lies transversely in the retroperitoneum behind the stomach. Its head is nestled into the "c-shaped" curvature of the duodenum with the body extending to the left about 15.2 cm (6 in) and ending as a tapering tail in the hilum of the spleen. It is a curious mix of exocrine (secr...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "The Pancreas", "token_count": 403, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pancreas produces over a liter of pancreatic juice each day. Unlike bile, it is clear and composed mostly of water along with some salts, sodium bicarbonate, and several digestive enzymes. Sodium bicarbonate is responsible for the slight alkalinity of pancreatic juice (pH 7.1 to 8.2), which serves to buffer the aci...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Pancreatic Juice", "token_count": 291, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Regulation of pancreatic secretion is the job of hormones and the parasympathetic nervous system. The entry of acidic chyme into the duodenum stimulates the release of secretin, which in turn causes the duct cells to release bicarbonaterich pancreatic juice. The presence of proteins and fats in the duodenum stimulates ...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Pancreatic Secretion", "token_count": 201, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The gallbladder is 8–10 cm (~3–4 in) long and is nested in a shallow area on the posterior aspect of the right lobe of the liver. This muscular sac stores, concentrates, and, when stimulated, propels the bile into the duodenum via the common bile duct. It is divided into three regions. The fundus is the widest port...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "The Gallbladder", "token_count": 361, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Identify the locations and primary secretions involved in the chemical digestion of carbohydrates, proteins, lipids, and nucleic acids - Compare and contrast absorption of the hydrophilic and hydrophobic nutrients As you have learned, the process of mechanical dige...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "token_count": 200, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Large food molecules (for example, proteins, lipids, nucleic acids, and starches) must be broken down into subunits that are small enough to be absorbed by the lining of the alimentary canal. This is accomplished by enzymes through hydrolysis. The many enzymes involved in chemical digestion are summarized in Table 23.8...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Chemical Digestion", "token_count": 265, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The average American diet is about 50 percent carbohydrates, which may be classified according to the number of monomers they contain of simple sugars (monosaccharides and disaccharides) and/or complex sugars (polysaccharides). Glucose, galactose, and fructose are the three monosaccharides that are commonly consumed an...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Carbohydrate Digestion", "token_count": 448, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Proteins are polymers composed of amino acids linked by peptide bonds to form long chains. Digestion reduces them to their constituent amino acids. You usually consume about 15 to 20 percent of your total calorie intake as protein. The digestion of protein starts in the stomach, where HCl and pepsin break proteins in...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Protein Digestion", "token_count": 298, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The mechanical and digestive processes have one goal: to convert food into molecules small enough to be absorbed by the epithelial cells of the intestinal villi. The absorptive capacity of the alimentary canal is almost endless. Each day, the alimentary canal processes up to 10 liters of food, liquids, and GI secretion...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Absorption", "token_count": 1137, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
About 95 percent of lipids are absorbed in the small intestine. Bile salts not only speed up lipid digestion, they are also essential to the absorption of the end products of lipid digestion. Short-chain fatty acids are relatively water soluble and can enter the absorptive cells (enterocytes) directly. Despite being hy...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Lipid Absorption", "token_count": 596, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The electrolytes absorbed by the small intestine are from both GI secretions and ingested foods. Since electrolytes dissociate into ions in water, most are absorbed via active transport throughout the entire small intestine. During absorption, cotransport mechanisms result in the accumulation of sodium ions inside the ...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Mineral Absorption", "token_count": 380, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
**absorption accessory digestive organ accessory duct acinus alimentary canal aminopeptidase anal canal anal column anal sinus appendix ascending colon bacterial flora bile bile canaliculus bilirubin body bolus brush border cardia cecum cementum central vein cephalic phase chemical digestion chief cell chylomicron chym...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "KEY TERMS", "token_count": 2048, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
buccal cavity) mouth oral vestibule part of the mouth bounded externally by the cheeks and lips, and internally by the gums and teeth oropharynx part of the pharynx continuous with the oral cavity that functions in respiration and digestion palatoglossal arch muscular fold that extends from the latera...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "KEY TERMS", "token_count": 1296, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the mouth, the tongue and the teeth begin mechanical digestion, and saliva begins chemical digestion. The pharynx, which plays roles in breathing and vocalization as well as digestion, runs from the nasal and oral cavities superiorly to the esophagus inferiorly (for digestion) and to the larynx anteriorly (for respi...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "[23.3 The Mouth, Pharynx, and Esophagus](#page-1048-0)", "token_count": 203, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The three main regions of the small intestine are the duodenum, the jejunum, and the ileum. The small intestine is where digestion is completed and virtually all absorption occurs. These two activities are facilitated by structural adaptations that increase the mucosal surface area by 600-fold, including circular folds...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "[23.5 The Small and Large Intestines](#page-1064-0)", "token_count": 274, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The small intestine is the site of most chemical digestion and almost all absorption. Chemical digestion breaks large food molecules down into their chemical building blocks, which can then be absorbed through the intestinal wall and into the general circulation. Intestinal brush border enzymes and pancreatic enzymes a...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "[23.7 Chemical Digestion and Absorption: A Closer Look](#page-1078-0)", "token_count": 214, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - Describe the processes involved in anabolic and catabolic reactions - List and describe the steps necessary for carbohydrate, lipid, and protein metabolism - Explain the processes that regulate glucose levels during the absorptive and postabsorptive states - Explain...	{ "Header 1": "Chapter Objectives", "token_count": 484, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the process by which polymers are broken down into monomers - Describe the process by which monomers are combined into polymers - Discuss the role of ATP in metabolism - Explain oxidation-reduction reactions - Describe the hormones that regulate anabolic and...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "token_count": 283, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Catabolic reactions break down large organic molecules into smaller molecules, releasing the energy contained in the chemical bonds. These energy releases (conversions) are not 100 percent efficient. The amount of energy released is less than the total amount contained in the molecule. Approximately 40 percent of e...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Catabolic Reactions", "token_count": 922, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
\| Hormone \| Function ...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Catabolic Hormones", "token_count": 240, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As might be expected for a fundamental physiological process like metabolism, errors or malfunctions in metabolic processing lead to a pathophysiology or—if uncorrected—a disease state. Metabolic diseases are most commonly the result of malfunctioning proteins or enzymes that are critical to one or more metabolic pathw...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Metabolic Processes: Cushing Syndrome and Addison's Disease", "token_count": 568, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The chemical reactions underlying metabolism involve the transfer of electrons from one compound to another by processes catalyzed by enzymes. The electrons in these reactions commonly come from hydrogen atoms, which consist of an electron and a proton. A molecule gives up a hydrogen atom, in the form of a hydrogen ion...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Oxidation-Reduction Reactions", "token_count": 347, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain the processes of glycolysis - Describe the pathway of a pyruvate molecule through the Krebs cycle - Explain the transport of electrons through the electron transport chain - Describe the process of ATP production through oxidative phosphorylation - Summarize ...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "token_count": 400, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Glucose is the body's most readily available source of energy. After digestive processes break polysaccharides down into monosaccharides, including glucose, the monosaccharides are transported across the wall of the small intestine and into the circulatory system, which transports them to the liver. In the liver, hepat...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Glycolysis", "token_count": 1888, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When oxygen is limited or absent, pyruvate enters an anaerobic pathway. In these reactions, pyruvate can be converted into lactic acid. In addition to generating an additional ATP, this pathway serves to keep the pyruvate concentration low so glycolysis continues, and it oxidizes NADH into the NAD<sup>+</sup> needed ...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Anaerobic Respiration", "token_count": 246, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the presence of oxygen, pyruvate can enter the Krebs cycle where additional energy is extracted as electrons are transferred from the pyruvate to the receptors NAD<sup>+</sup> , GDP, and FAD, with carbon dioxide being a "waste product" ([Figure](#page-1109-0) [24.6](#page-1109-0)). The NADH and FADH2 pass electr...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Aerobic Respiration", "token_count": 225, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pyruvate molecules generated during glycolysis are transported across the mitochondrial membrane into the inner mitochondrial matrix, where they are metabolized by enzymes in a pathway called the Krebs cycle ([Figure 24.7](#page-1110-0)). The Krebs cycle is also commonly called the citric acid cycle or the ...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Krebs Cycle/Citric Acid Cycle/Tricarboxylic Acid Cycle", "token_count": 934, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The electron transport chain (ETC) uses the NADH and FADH2 produced by the Krebs cycle to generate ATP. Electrons from NADH and FADH2 are transferred through protein complexes embedded in the inner mitochondrial membrane by a series of enzymatic reactions. The electron transport chain consists of a series of four e...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Oxidative Phosphorylation and the Electron Transport Chain", "token_count": 932, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Gluconeogenesis is the synthesis of new glucose molecules from pyruvate, lactate, glycerol, or the amino acids alanine or glutamine. This process takes place primarily in the liver during periods of low glucose, that is, under conditions of fasting, starvation, and low carbohydrate diets. So, the question can be ra...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Gluconeogenesis", "token_count": 608, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The human body's metabolic rate decreases nearly 2 percent per decade after age 30. Changes in body composition, including reduced lean muscle mass, are mostly responsible for this decrease. The most dramatic loss of muscle mass, and consequential decline in metabolic rate, occurs between 50 and 70 years of age. Loss o...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Body's Metabolic Rate", "token_count": 267, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain how energy can be derived from fat - Explain the purpose and process of ketogenesis - Describe the process of ketone body oxidation - Explain the purpose and the process of lipogenesis Fats (or triglycerides) within the body are ingested as food or synthesi...	{ "Header 1": "24.3 \| Lipid Metabolism", "token_count": 688, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. This process, called lipolysis, takes place in the cytoplasm. The resulting fatty acids are oxidized by βoxidation into acetyl CoA, which is used by the Krebs cycle. The gl...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Lipolysis", "token_count": 418, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create ketone bodies. These ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starv...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Ketogenesis", "token_count": 290, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Organs that have classically been thought to be dependent solely on glucose, such as the brain, can actually use ketones as an alternative energy source. This keeps the brain functioning when glucose is limited. When ketones are produced faster than they can be used, they can be broken down into CO2 and acetone. The ac...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Ketone Body Oxidation", "token_count": 340, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When glucose levels are plentiful, the excess acetyl CoA generated by glycolysis can be converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts. This process, called lipogenesis, creates lipids (fat) from the acetyl CoA and takes place in the cytoplasm of adipocytes (fat cells) and hepatocy...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Lipogenesis", "token_count": 527, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe how the body digests proteins - Explain how the urea cycle prevents toxic concentrations of nitrogen - Differentiate between glucogenic and ketogenic amino acids - Explain how protein can be used for energy Much of the body is made of protein, and these pr...	{ "Header 1": "24.4 \| Protein Metabolism", "token_count": 977, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The urea cycle is a set of biochemical reactions that produces urea from ammonium ions in order to prevent a toxic level of ammonium in the body. It occurs primarily in the liver and, to a lesser extent, in the kidney. Prior to the urea cycle, ammonium ions are produced from the breakdown of amino acids. In these r...	{ "Header 1": "24.4 \| Protein Metabolism", "Header 3": "Urea Cycle", "token_count": 547, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Pyruvate dehydrogenase complex deficiency (PDCD) and phenylketonuria (PKU) are genetic disorders. Pyruvate dehydrogenase is the enzyme that converts pyruvate into acetyl CoA, the molecule necessary to begin the Krebs cycle to produce ATP. With low levels of the pyruvate dehydrogenase complex (PDC), the rate of cycling ...	{ "Header 1": "24.4 \| Protein Metabolism", "Header 2": "Metabolism: Pyruvate Dehydrogenase Complex Deficiency and Phenylketonuria", "token_count": 477, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The absorptive state, or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients (catabolism exceeds anabolism). Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine. The diges...	{ "Header 1": "24.5 \| Metabolic States of the Body", "Header 3": "The Absorptive State", "token_count": 505, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The postabsorptive state, or the fasting state, occurs when the food has been digested, absorbed, and stored. You commonly fast overnight, but skipping meals during the day puts your body in the postabsorptive state as well. During this state, the body must rely initially on stored glycogen. Glucose levels in t...	{ "Header 1": "24.5 \| Metabolic States of the Body", "Header 3": "The Postabsorptive State", "token_count": 448, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When the body is deprived of nourishment for an extended period of time, it goes into "survival mode." The first priority for survival is to provide enough glucose or fuel for the brain. The second priority is the conservation of amino acids for proteins. Therefore, the body uses ketones to satisfy the energy needs of ...	{ "Header 1": "24.5 \| Metabolic States of the Body", "Header 3": "Starvation", "token_count": 335, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe how the body regulates temperature - Explain the significance of the metabolic rate The body tightly regulates the body temperature through a process called thermoregulation, in which the body can maintain its temperature within certain boundaries, eve...	{ "Header 1": "24.6 \| Energy and Heat Balance", "token_count": 433, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When the environment is not thermoneutral, the body uses four mechanisms of heat exchange to maintain homeostasis: conduction, convection, radiation, and evaporation. Each of these mechanisms relies on the property of heat to flow from a higher concentration to a lower concentration; therefore, each of the mechanisms o...	{ "Header 1": "24.6 \| Energy and Heat Balance", "Header 3": "Mechanisms of Heat Exchange", "token_count": 503, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The amount of energy that is needed or ingested per day is measured in calories. The nutritional Calorie (C) is the amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C. This is different from the calorie (c) used in the physical sciences, which is the amount of heat it takes to raise 1 g of water by 1 °...	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Food and Metabolism", "token_count": 723, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Obesity in the United States is epidemic. The rate of obesity has been steadily rising since the 1980s. In the 1990s, most states reported that less than 10 percent of their populations was obese, and the state with the highest rate reported that only 15 percent of their population was considered obese. By 2010, the U....	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Metabolism and Obesity", "token_count": 397, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Vitamins are organic compounds found in foods and are a necessary part of the biochemical reactions in the body. They are involved in a number of processes, including mineral and bone metabolism, and cell and tissue growth, and they act as cofactors for energy metabolism. The B vitamins play the largest role of any...	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Vitamins", "token_count": 601, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Minerals in food are inorganic compounds that work with other nutrients to ensure the body functions properly. Minerals cannot be made in the body; they come from the diet. The amount of minerals in the body is small—only 4 percent of the total body mass—and most of that consists of the minerals that the body requi...	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Minerals", "token_count": 456, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }

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Normally, the respiratory centers of the brain maintain a consistent, rhythmic breathing cycle. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high ...	{ "Header 1": "22.7 \| Embryonic Development of the Respiratory System", "Header 3": "[22.6 Modifications in Respiratory Functions](#page-1024-0)", "token_count": 339, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The development of the respiratory system in the fetus begins at about 4 weeks and continues into childhood. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx. At about this same time, an protru...	{ "Header 1": "22.7 \| Embryonic Development of the Respiratory System", "Header 3": "[22.7 Embryonic Development of the Respiratory System](#page-1025-0)", "token_count": 357, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - List and describe the functional anatomy of the organs and accessory organs of the digestive system - Discuss the processes and control of ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation - Discuss the roles of the liver, p...	{ "Header 1": "Introduction", "Header 2": "Chapter Objectives", "token_count": 281, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Identify the organs of the alimentary canal from proximal to distal, and briefly state their function - Identify the accessory digestive organs and briefly state their function - Describe the four fundamental tissue layers of the alimentary canal - Contrast the contr...	{ "Header 1": "23.1 \| Overview of the Digestive System", "token_count": 488, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Throughout its length, the alimentary tract is composed of the same four tissue layers; the details of their structural arrangements vary to fit their specific functions. Starting from the lumen and moving outwards, these layers are the mucosa, submucosa, muscularis, and serosa, which is continuous with the mesentery (...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Histology of the Alimentary Canal", "token_count": 1063, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As soon as food enters the mouth, it is detected by receptors that send impulses along the sensory neurons of cranial nerves. Without these nerves, not only would your food be without taste, but you would also be unable to feel either the food or the structures of your mouth, and you would be unable to avoid biting you...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Nerve Supply", "token_count": 374, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The blood vessels serving the digestive system have two functions. They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen. Lipids are absorbed via lacteals, tiny structures of the lymphatic system. The blood vessels' second function is to supply the organs of...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Blood Supply", "token_count": 277, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which ...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "The Peritoneum", "token_count": 204, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Inflammation of the peritoneum is called peritonitis. Chemical peritonitis can develop any time the wall of the alimentary canal is breached, allowing the contents of the lumen entry into the peritoneal cavity. For example, when an ulcer perforates the stomach wall, gastric juices spill into the peritoneal cavity. Hemo...	{ "Header 1": "23.1 \| Overview of the Digestive System", "Header 3": "Digestive System: Peritonitis", "token_count": 478, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation. The first of these processes, ingestion, refers to the entry of food into the alimentary canal through the mouth. There, the food is chewed and mixed with sal...	{ "Header 1": "23.2 \| Digestive System Processes and Regulation", "Header 3": "Digestive Processes", "token_count": 764, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Age-related changes in the digestive system begin in the mouth and can affect virtually every aspect of the digestive system. Taste buds become less sensitive, so food isn't as appetizing as it once was. A slice of pizza is a challenge, not a treat, when you have lost teeth, your gums are diseased, and your salivary gl...	{ "Header 1": "23.2 \| Digestive System Processes and Regulation", "Header 3": "Digestive System: From Appetite Suppression to Constipation", "token_count": 393, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The walls of the alimentary canal contain a variety of sensors that help regulate digestive functions. These include mechanoreceptors, chemoreceptors, and osmoreceptors, which are capable of detecting mechanical, chemical, and osmotic stimuli, respectively. For example, these receptors can sense when the presence of fo...	{ "Header 1": "23.2 \| Digestive System Processes and Regulation", "Header 3": "Neural Controls", "token_count": 408, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The cheeks, tongue, and palate frame the mouth, which is also called the oral cavity (or buccal cavity). The structures of the mouth are illustrated in [Figure 23.7](#page-1049-0). At the entrance to the mouth are the lips, or labia (singular = labium). Their outer covering is skin, which transitions to a...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Mouth", "token_count": 857, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Perhaps you have heard it said that the tongue is the strongest muscle in the body. Those who stake this claim cite its strength proportionate to its size. Although it is difficult to quantify the relative strength of different muscles, it remains indisputable that the tongue is a workhorse, facilitating ingestion,...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Tongue", "token_count": 783, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Saliva is essentially (95.5 percent) water. The remaining 4.5 percent is a complex mixture of ions, glycoproteins, enzymes, growth factors, and waste products. Perhaps the most important ingredient in salvia from the perspective of digestion is the enzyme salivary amylase, which initiates the breakdown of carbo...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Saliva", "token_count": 405, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Infections of the nasal passages and pharynx can attack any salivary gland. The parotid glands are the usual site of infection with the virus that causes mumps (paramyxovirus). Mumps manifests by enlargement and inflammation of the parotid glands, causing a characteristic swelling between the ears and the jaw. Symptoms...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Parotid Glands: Mumps", "token_count": 207, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The autonomic nervous system regulates salivation (the secretion of saliva). In the absence of food, parasympathetic stimulation keeps saliva flowing at just the right level for comfort as you speak, swallow, sleep, and generally go about life. Over-salivation can occur, for example, if you are stimulated by the sm...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Regulation of Salivation", "token_count": 335, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
During the course of your lifetime, you have two sets of teeth (one set of teeth is a dentition). Your 20 deciduous teeth, or baby teeth, first begin to appear at about 6 months of age. Between approximately age 6 and 12, these teeth are replaced by 32 permanent teeth. Moving from the center of the mouth to...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Types of Teeth", "token_count": 390, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The teeth are secured in the alveolar processes (sockets) of the maxilla and the mandible. Gingivae (commonly called the gums) are soft tissues that line the alveolar processes and surround the necks of the teeth. Teeth are also held in their sockets by a connective tissue called the periodontal ligament. The two...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Anatomy of a Tooth", "token_count": 760, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pharynx (throat) is involved in both digestion and respiration. It receives food and air from the mouth, and air from the nasal cavities. When food enters the pharynx, involuntary muscle contractions close off the air passageways. A short tube of skeletal muscle lined with a mucous membrane, the pharynx runs ...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Pharynx", "token_count": 543, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The upper esophageal sphincter, which is continuous with the inferior pharyngeal constrictor, controls the movement of food from the pharynx into the esophagus. The upper two-thirds of the esophagus consists of both smooth and skeletal muscle fibers, with the latter fading out in the bottom third of the esophagus. ...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Passage of Food through the Esophagus", "token_count": 371, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The mucosa of the esophagus is made up of an epithelial lining that contains non-keratinized, stratified squamous epithelium, with a layer of basal and parabasal cells. This epithelium protects against erosion from food particles. The mucosa's lamina propria contains mucus-secreting glands. The muscularis layer changes...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Histology of the Esophagus", "token_count": 357, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Deglutition is another word for swallowing—the movement of food from the mouth to the stomach. The entire process takes about 4 to 8 seconds for solid or semisolid food, and about 1 second for very soft food and liquids. Although this sounds quick and effortless, deglutition is, in fact, a complex process that invo...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "Deglutition", "token_count": 216, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of peristalsis. As in the previous phase, the complex neuromuscular actions are controlled by the medulla oblongata. Peristalsis propels the bolus through the esophagus and toward the stomach. The circular...	{ "Header 1": "23.3 \| The Mouth, Pharynx, and Esophagus", "Header 3": "The Esophageal Phase", "token_count": 306, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Label on a diagram the four main regions of the stomach, its curvatures, and its sphincter - Identify the four main types of secreting cells in gastric glands, and their important products - Explain why the stomach does not digest itself - Describe the mechanical and...	{ "Header 1": "23.4 \| The Stomach", "token_count": 472, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
There are four main regions in the stomach: the cardia, fundus, body, and pylorus ([Figure 23.15](#page-1059-0)). The cardia (or cardiac region) is the point where the esophagus connects to the stomach and through which food passes into the stomach. Located inferior to the diaphragm, above and to the left o...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Structure", "token_count": 376, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The wall of the stomach is made of the same four layers as most of the rest of the alimentary canal, but with adaptations to the mucosa and muscularis for the unique functions of this organ. In addition to the typical circular and longitudinal smooth muscle layers, the muscularis has an inner oblique smooth muscle laye...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Histology", "token_count": 1210, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The secretion of gastric juice is controlled by both nerves and hormones. Stimuli in the brain, stomach, and small intestine activate or inhibit gastric juice production. This is why the three phases of gastric secretion are called the cephalic, gastric, and intestinal phases (Figure 23.17). However, once gastric secre...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Gastric Secretion", "token_count": 608, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As effective as the mucosal barrier is, it is not a "fail-safe" mechanism. Sometimes, gastric juice eats away at the superficial lining of the stomach mucosa, creating erosions, which mostly heal on their own. Deeper and larger erosions are called ulcers. Why does the mucosal barrier break down? A number of factors c...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Ulcers: When the Mucosal Barrier Breaks Down", "token_count": 228, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Within a few moments after food after enters your stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave is a unique type of peristalsis that mixes and softens the food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed b...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Mechanical Digestion", "token_count": 329, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The fundus plays an important role, because it stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue...	{ "Header 1": "23.4 \| The Stomach", "Header 3": "Chemical Digestion", "token_count": 397, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Compare and contrast the location and gross anatomy of the small and large intestines - Identify three main adaptations of the small intestine wall that increase its absorptive capacity - Describe the mechanical and chemical digestion of chyme upon its release into t...	{ "Header 1": "23.5 \| The Small and Large Intestines", "token_count": 200, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Chyme released from the stomach enters the small intestine, which is the primary digestive organ in the body. Not only is this where most digestion occurs, it is also where practically all absorption occurs. The longest part of the alimentary canal, the small intestine is about 3.05 meters (10 feet) long in a livin...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "The Small Intestine", "token_count": 232, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The coiled tube of the small intestine is subdivided into three regions. From proximal (at the stomach) to distal, these are the duodenum, jejunum, and ileum ([Figure 23.18](#page-1065-0)). The shortest region is the 25.4-cm (10-in) duodenum, which begins at the pyloric sphincter. Just past the pyloric sphinc...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Structure", "token_count": 668, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The wall of the small intestine is composed of the same four layers typically present in the alimentary system. However, three features of the mucosa and submucosa are unique. These features, which increase the absorptive surface area of the small intestine more than 600-fold, include circular folds, villi, and microvi...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Histology", "token_count": 262, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In addition to the three specialized absorptive features just discussed, the mucosa between the villi is dotted with deep crevices that each lead into a tubular intestinal gland (crypt of Lieberkühn), which is formed by cells that line the crevices (see [Figure 23.19](#page-1066-0)). These produce **intestinal ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Intestinal Glands", "token_count": 545, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The lamina propria of the small intestine mucosa is studded with quite a bit of MALT. In addition to solitary lymphatic nodules, aggregations of intestinal MALT, which are typically referred to as Peyer's patches, are concentrated in the distal ileum, and serve to keep bacteria from entering the bloodstream. Peyer's pa...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Intestinal MALT", "token_count": 235, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The movement of intestinal smooth muscles includes both segmentation and a form of peristalsis called migrating motility complexes. The kind of peristaltic mixing waves seen in the stomach are not observed here. If you could see into the small intestine when it was going through segmentation, it would look as if the ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Mechanical Digestion in the Small Intestine", "token_count": 599, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The digestion of proteins and carbohydrates, which partially occurs in the stomach, is completed in the small intestine with the aid of intestinal and pancreatic juices. Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancre...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Chemical Digestion in the Small Intestine", "token_count": 309, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Lactose intolerance is a condition characterized by indigestion caused by dairy products. It occurs when the absorptive cells of the small intestine do not produce enough lactase, the enzyme that digests the milk sugar lactose. In most mammals, lactose intolerance increases with age. In contrast, some human populations...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Small Intestine: Lactose Intolerance", "token_count": 275, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The first part of the large intestine is the cecum, a sac-like structure that is suspended inferior to the ileocecal valve. It is about 6 cm (2.4 in) long, receives the contents of the ileum, and continues the absorption of water and salts. The appendix (or vermiform appendix) is a winding tube that attaches to...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Cecum", "token_count": 212, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The cecum blends seamlessly with the colon. Upon entering the colon, the food residue first travels up the ascending colon on the right side of the abdomen. At the inferior surface of the liver, the colon bends to form the right colic flexure (hepatic flexure) and becomes the transverse colon. The regio...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Colon", "token_count": 314, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Each year, approximately 140,000 Americans are diagnosed with colorectal cancer, and another 49,000 die from it, making it one of the most deadly malignancies. People with a family history of colorectal cancer are at increased risk. Smoking, excessive alcohol consumption, and a diet high in animal fat and protein also ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Colorectal Cancer", "token_count": 231, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
There are several notable differences between the walls of the large and small intestines ([Figure 23.22](#page-1071-0)). For example, few enzyme-secreting cells are found in the wall of the large intestine, and there are no circular folds or villi. Other than in the anal canal, the mucosa of the colon is simple co...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Histology", "token_count": 292, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Three features are unique to the large intestine: teniae coli, haustra, and epiploic appendages ([Figure 23.23](#page-1072-0)). The teniae coli are three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. Tonic contractions of ...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Anatomy", "token_count": 213, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The stratified squamous epithelial mucosa of the anal canal connects to the skin on the outside of the anus. This mucosa varies considerably from that of the rest of the colon to accommodate the high level of abrasion as feces pass through. The anal canal's mucous membrane is organized into longitudinal folds, each cal...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Figure 23.23 Teniae Coli, Haustra, and Epiploic Appendages", "token_count": 234, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Most bacteria that enter the alimentary canal are killed by lysozyme, defensins, HCl, or protein-digesting enzymes. However, trillions of bacteria live within the large intestine and are referred to as the bacterial flora. Most of the more than 700 species of these bacteria are nonpathogenic commensal organisms tha...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Bacterial Flora", "token_count": 281, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the large intestine, mechanical digestion begins when chyme moves from the ileum into the cecum, an activity regulated by the ileocecal sphincter. Right after you eat, peristalsis in the ileum forces chyme into the cecum. When the cecum is distended with chyme, contractions of the ileocecal sphincter strengthen. Onc...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Mechanical Digestion", "token_count": 355, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The small intestine absorbs about 90 percent of the water you ingest (either as liquid or within solid food). The large intestine absorbs most of the remaining water, a process that converts the liquid chyme residue into semisolid feces ("stool"). Feces is composed of undigested food residues, unabsorbed digested s...	{ "Header 1": "23.5 \| The Small and Large Intestines", "Header 3": "Absorption, Feces Formation, and Defecation", "token_count": 607, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - State the main digestive roles of the liver, pancreas, and gallbladder - Identify three main features of liver histology that are critical to its function - Discuss the composition and function of bile - Identify the major types of enzymes and buffers present in panc...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "token_count": 232, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The liver is the largest gland in the body, weighing about three pounds in an adult. It is also one of the most important organs. In addition to being an accessory digestive organ, it plays a number of roles in metabolism and regulation. The liver lies inferior to the diaphragm in the right upper quadrant of the ab...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "The Liver", "token_count": 537, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The liver has three main components: hepatocytes, bile canaliculi, and hepatic sinusoids. A hepatocyte is the liver's main cell type, accounting for around 80 percent of the liver's volume. These cells play a role in a wide variety of secretory, metabolic, and endocrine functions. Plates of hepatocytes called hepat...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Histology", "token_count": 488, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Recall that lipids are hydrophobic, that is, they do not dissolve in water. Thus, before they can be digested in the watery environment of the small intestine, large lipid globules must be broken down into smaller lipid globules, a process called emulsification. Bile is a mixture secreted by the liver to accomplish...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Bile", "token_count": 744, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The soft, oblong, glandular pancreas lies transversely in the retroperitoneum behind the stomach. Its head is nestled into the "c-shaped" curvature of the duodenum with the body extending to the left about 15.2 cm (6 in) and ending as a tapering tail in the hilum of the spleen. It is a curious mix of exocrine (secr...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "The Pancreas", "token_count": 403, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pancreas produces over a liter of pancreatic juice each day. Unlike bile, it is clear and composed mostly of water along with some salts, sodium bicarbonate, and several digestive enzymes. Sodium bicarbonate is responsible for the slight alkalinity of pancreatic juice (pH 7.1 to 8.2), which serves to buffer the aci...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Pancreatic Juice", "token_count": 291, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Regulation of pancreatic secretion is the job of hormones and the parasympathetic nervous system. The entry of acidic chyme into the duodenum stimulates the release of secretin, which in turn causes the duct cells to release bicarbonaterich pancreatic juice. The presence of proteins and fats in the duodenum stimulates ...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "Pancreatic Secretion", "token_count": 201, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The gallbladder is 8–10 cm (~3–4 in) long and is nested in a shallow area on the posterior aspect of the right lobe of the liver. This muscular sac stores, concentrates, and, when stimulated, propels the bile into the duodenum via the common bile duct. It is divided into three regions. The fundus is the widest port...	{ "Header 1": "23.6 \| Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder", "Header 3": "The Gallbladder", "token_count": 361, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Identify the locations and primary secretions involved in the chemical digestion of carbohydrates, proteins, lipids, and nucleic acids - Compare and contrast absorption of the hydrophilic and hydrophobic nutrients As you have learned, the process of mechanical dige...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "token_count": 200, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Large food molecules (for example, proteins, lipids, nucleic acids, and starches) must be broken down into subunits that are small enough to be absorbed by the lining of the alimentary canal. This is accomplished by enzymes through hydrolysis. The many enzymes involved in chemical digestion are summarized in Table 23.8...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Chemical Digestion", "token_count": 265, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The average American diet is about 50 percent carbohydrates, which may be classified according to the number of monomers they contain of simple sugars (monosaccharides and disaccharides) and/or complex sugars (polysaccharides). Glucose, galactose, and fructose are the three monosaccharides that are commonly consumed an...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Carbohydrate Digestion", "token_count": 448, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Proteins are polymers composed of amino acids linked by peptide bonds to form long chains. Digestion reduces them to their constituent amino acids. You usually consume about 15 to 20 percent of your total calorie intake as protein. The digestion of protein starts in the stomach, where HCl and pepsin break proteins in...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Protein Digestion", "token_count": 298, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The mechanical and digestive processes have one goal: to convert food into molecules small enough to be absorbed by the epithelial cells of the intestinal villi. The absorptive capacity of the alimentary canal is almost endless. Each day, the alimentary canal processes up to 10 liters of food, liquids, and GI secretion...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Absorption", "token_count": 1137, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
About 95 percent of lipids are absorbed in the small intestine. Bile salts not only speed up lipid digestion, they are also essential to the absorption of the end products of lipid digestion. Short-chain fatty acids are relatively water soluble and can enter the absorptive cells (enterocytes) directly. Despite being hy...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Lipid Absorption", "token_count": 596, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The electrolytes absorbed by the small intestine are from both GI secretions and ingested foods. Since electrolytes dissociate into ions in water, most are absorbed via active transport throughout the entire small intestine. During absorption, cotransport mechanisms result in the accumulation of sodium ions inside the ...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "Mineral Absorption", "token_count": 380, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
**absorption accessory digestive organ accessory duct acinus alimentary canal aminopeptidase anal canal anal column anal sinus appendix ascending colon bacterial flora bile bile canaliculus bilirubin body bolus brush border cardia cecum cementum central vein cephalic phase chemical digestion chief cell chylomicron chym...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "KEY TERMS", "token_count": 2048, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
buccal cavity) mouth oral vestibule part of the mouth bounded externally by the cheeks and lips, and internally by the gums and teeth oropharynx part of the pharynx continuous with the oral cavity that functions in respiration and digestion palatoglossal arch muscular fold that extends from the latera...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "KEY TERMS", "token_count": 1296, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the mouth, the tongue and the teeth begin mechanical digestion, and saliva begins chemical digestion. The pharynx, which plays roles in breathing and vocalization as well as digestion, runs from the nasal and oral cavities superiorly to the esophagus inferiorly (for digestion) and to the larynx anteriorly (for respi...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "[23.3 The Mouth, Pharynx, and Esophagus](#page-1048-0)", "token_count": 203, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The three main regions of the small intestine are the duodenum, the jejunum, and the ileum. The small intestine is where digestion is completed and virtually all absorption occurs. These two activities are facilitated by structural adaptations that increase the mucosal surface area by 600-fold, including circular folds...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "[23.5 The Small and Large Intestines](#page-1064-0)", "token_count": 274, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The small intestine is the site of most chemical digestion and almost all absorption. Chemical digestion breaks large food molecules down into their chemical building blocks, which can then be absorbed through the intestinal wall and into the general circulation. Intestinal brush border enzymes and pancreatic enzymes a...	{ "Header 1": "23.7 \| Chemical Digestion and Absorption: A Closer Look", "Header 3": "[23.7 Chemical Digestion and Absorption: A Closer Look](#page-1078-0)", "token_count": 214, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
After studying this chapter, you will be able to: - Describe the processes involved in anabolic and catabolic reactions - List and describe the steps necessary for carbohydrate, lipid, and protein metabolism - Explain the processes that regulate glucose levels during the absorptive and postabsorptive states - Explain...	{ "Header 1": "Chapter Objectives", "token_count": 484, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe the process by which polymers are broken down into monomers - Describe the process by which monomers are combined into polymers - Discuss the role of ATP in metabolism - Explain oxidation-reduction reactions - Describe the hormones that regulate anabolic and...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "token_count": 283, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Catabolic reactions break down large organic molecules into smaller molecules, releasing the energy contained in the chemical bonds. These energy releases (conversions) are not 100 percent efficient. The amount of energy released is less than the total amount contained in the molecule. Approximately 40 percent of e...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Catabolic Reactions", "token_count": 922, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
\| Hormone \| Function ...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Catabolic Hormones", "token_count": 240, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
As might be expected for a fundamental physiological process like metabolism, errors or malfunctions in metabolic processing lead to a pathophysiology or—if uncorrected—a disease state. Metabolic diseases are most commonly the result of malfunctioning proteins or enzymes that are critical to one or more metabolic pathw...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Metabolic Processes: Cushing Syndrome and Addison's Disease", "token_count": 568, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The chemical reactions underlying metabolism involve the transfer of electrons from one compound to another by processes catalyzed by enzymes. The electrons in these reactions commonly come from hydrogen atoms, which consist of an electron and a proton. A molecule gives up a hydrogen atom, in the form of a hydrogen ion...	{ "Header 1": "24.1 \| Overview of Metabolic Reactions", "Header 3": "Oxidation-Reduction Reactions", "token_count": 347, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain the processes of glycolysis - Describe the pathway of a pyruvate molecule through the Krebs cycle - Explain the transport of electrons through the electron transport chain - Describe the process of ATP production through oxidative phosphorylation - Summarize ...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "token_count": 400, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Glucose is the body's most readily available source of energy. After digestive processes break polysaccharides down into monosaccharides, including glucose, the monosaccharides are transported across the wall of the small intestine and into the circulatory system, which transports them to the liver. In the liver, hepat...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Glycolysis", "token_count": 1888, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When oxygen is limited or absent, pyruvate enters an anaerobic pathway. In these reactions, pyruvate can be converted into lactic acid. In addition to generating an additional ATP, this pathway serves to keep the pyruvate concentration low so glycolysis continues, and it oxidizes NADH into the NAD<sup>+</sup> needed ...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Anaerobic Respiration", "token_count": 246, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
In the presence of oxygen, pyruvate can enter the Krebs cycle where additional energy is extracted as electrons are transferred from the pyruvate to the receptors NAD<sup>+</sup> , GDP, and FAD, with carbon dioxide being a "waste product" ([Figure](#page-1109-0) [24.6](#page-1109-0)). The NADH and FADH2 pass electr...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Aerobic Respiration", "token_count": 225, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The pyruvate molecules generated during glycolysis are transported across the mitochondrial membrane into the inner mitochondrial matrix, where they are metabolized by enzymes in a pathway called the Krebs cycle ([Figure 24.7](#page-1110-0)). The Krebs cycle is also commonly called the citric acid cycle or the ...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Krebs Cycle/Citric Acid Cycle/Tricarboxylic Acid Cycle", "token_count": 934, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The electron transport chain (ETC) uses the NADH and FADH2 produced by the Krebs cycle to generate ATP. Electrons from NADH and FADH2 are transferred through protein complexes embedded in the inner mitochondrial membrane by a series of enzymatic reactions. The electron transport chain consists of a series of four e...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Oxidative Phosphorylation and the Electron Transport Chain", "token_count": 932, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Gluconeogenesis is the synthesis of new glucose molecules from pyruvate, lactate, glycerol, or the amino acids alanine or glutamine. This process takes place primarily in the liver during periods of low glucose, that is, under conditions of fasting, starvation, and low carbohydrate diets. So, the question can be ra...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Gluconeogenesis", "token_count": 608, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The human body's metabolic rate decreases nearly 2 percent per decade after age 30. Changes in body composition, including reduced lean muscle mass, are mostly responsible for this decrease. The most dramatic loss of muscle mass, and consequential decline in metabolic rate, occurs between 50 and 70 years of age. Loss o...	{ "Header 1": "24.2 \| Carbohydrate Metabolism", "Header 3": "Body's Metabolic Rate", "token_count": 267, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Explain how energy can be derived from fat - Explain the purpose and process of ketogenesis - Describe the process of ketone body oxidation - Explain the purpose and the process of lipogenesis Fats (or triglycerides) within the body are ingested as food or synthesi...	{ "Header 1": "24.3 \| Lipid Metabolism", "token_count": 688, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. This process, called lipolysis, takes place in the cytoplasm. The resulting fatty acids are oxidized by βoxidation into acetyl CoA, which is used by the Krebs cycle. The gl...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Lipolysis", "token_count": 418, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create ketone bodies. These ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starv...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Ketogenesis", "token_count": 290, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Organs that have classically been thought to be dependent solely on glucose, such as the brain, can actually use ketones as an alternative energy source. This keeps the brain functioning when glucose is limited. When ketones are produced faster than they can be used, they can be broken down into CO2 and acetone. The ac...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Ketone Body Oxidation", "token_count": 340, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When glucose levels are plentiful, the excess acetyl CoA generated by glycolysis can be converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts. This process, called lipogenesis, creates lipids (fat) from the acetyl CoA and takes place in the cytoplasm of adipocytes (fat cells) and hepatocy...	{ "Header 1": "24.3 \| Lipid Metabolism", "Header 3": "Lipogenesis", "token_count": 527, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe how the body digests proteins - Explain how the urea cycle prevents toxic concentrations of nitrogen - Differentiate between glucogenic and ketogenic amino acids - Explain how protein can be used for energy Much of the body is made of protein, and these pr...	{ "Header 1": "24.4 \| Protein Metabolism", "token_count": 977, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The urea cycle is a set of biochemical reactions that produces urea from ammonium ions in order to prevent a toxic level of ammonium in the body. It occurs primarily in the liver and, to a lesser extent, in the kidney. Prior to the urea cycle, ammonium ions are produced from the breakdown of amino acids. In these r...	{ "Header 1": "24.4 \| Protein Metabolism", "Header 3": "Urea Cycle", "token_count": 547, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Pyruvate dehydrogenase complex deficiency (PDCD) and phenylketonuria (PKU) are genetic disorders. Pyruvate dehydrogenase is the enzyme that converts pyruvate into acetyl CoA, the molecule necessary to begin the Krebs cycle to produce ATP. With low levels of the pyruvate dehydrogenase complex (PDC), the rate of cycling ...	{ "Header 1": "24.4 \| Protein Metabolism", "Header 2": "Metabolism: Pyruvate Dehydrogenase Complex Deficiency and Phenylketonuria", "token_count": 477, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The absorptive state, or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients (catabolism exceeds anabolism). Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine. The diges...	{ "Header 1": "24.5 \| Metabolic States of the Body", "Header 3": "The Absorptive State", "token_count": 505, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The postabsorptive state, or the fasting state, occurs when the food has been digested, absorbed, and stored. You commonly fast overnight, but skipping meals during the day puts your body in the postabsorptive state as well. During this state, the body must rely initially on stored glycogen. Glucose levels in t...	{ "Header 1": "24.5 \| Metabolic States of the Body", "Header 3": "The Postabsorptive State", "token_count": 448, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When the body is deprived of nourishment for an extended period of time, it goes into "survival mode." The first priority for survival is to provide enough glucose or fuel for the brain. The second priority is the conservation of amino acids for proteins. Therefore, the body uses ketones to satisfy the energy needs of ...	{ "Header 1": "24.5 \| Metabolic States of the Body", "Header 3": "Starvation", "token_count": 335, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
By the end of this section, you will be able to: - Describe how the body regulates temperature - Explain the significance of the metabolic rate The body tightly regulates the body temperature through a process called thermoregulation, in which the body can maintain its temperature within certain boundaries, eve...	{ "Header 1": "24.6 \| Energy and Heat Balance", "token_count": 433, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
When the environment is not thermoneutral, the body uses four mechanisms of heat exchange to maintain homeostasis: conduction, convection, radiation, and evaporation. Each of these mechanisms relies on the property of heat to flow from a higher concentration to a lower concentration; therefore, each of the mechanisms o...	{ "Header 1": "24.6 \| Energy and Heat Balance", "Header 3": "Mechanisms of Heat Exchange", "token_count": 503, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
The amount of energy that is needed or ingested per day is measured in calories. The nutritional Calorie (C) is the amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C. This is different from the calorie (c) used in the physical sciences, which is the amount of heat it takes to raise 1 g of water by 1 °...	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Food and Metabolism", "token_count": 723, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Obesity in the United States is epidemic. The rate of obesity has been steadily rising since the 1980s. In the 1990s, most states reported that less than 10 percent of their populations was obese, and the state with the highest rate reported that only 15 percent of their population was considered obese. By 2010, the U....	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Metabolism and Obesity", "token_count": 397, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Vitamins are organic compounds found in foods and are a necessary part of the biochemical reactions in the body. They are involved in a number of processes, including mineral and bone metabolism, and cell and tissue growth, and they act as cofactors for energy metabolism. The B vitamins play the largest role of any...	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Vitamins", "token_count": 601, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }
Minerals in food are inorganic compounds that work with other nutrients to ensure the body functions properly. Minerals cannot be made in the body; they come from the diet. The amount of minerals in the body is small—only 4 percent of the total body mass—and most of that consists of the minerals that the body requi...	{ "Header 1": "24.7 \| Nutrition and Diet", "Header 3": "Minerals", "token_count": 456, "source_pdf": "datasets/websources/Med_v1/med_textbook/AnatomyAndPhysiology-LR.pdf" }