XIV Glossary

Acinus: A small, grape-like cluster of cells in the pancreas that produces and secretes digestive enzymes as part of its exocrine function. (Chapter 14.3)

Alimentary canal: Another term for the gastrointestinal tract; it is the muscular tube through which food passes, is digested, and waste is eliminated. (Chapter 14.1)

Anabolism: Uses the energy produced by catabolic reactions to build larger molecules from smaller ones, such as when the body forms proteins by stringing together amino acids. (Chapter 14.4)

Anal canal: The final 1.5–2 inches of the large intestine that opens to the exterior at the anus and contains both internal and external sphincters to regulate defecation. (Chapter 14.3)

Appendicitis: A condition in which the appendix becomes inflamed and is a common reason for emergency surgery. (Chapter 14.5)

Appendix: A winding, approximately 3-inch-long tube attached to the cecum that contains lymphatic tissue and is generally considered vestigial with a possible immune role. (Chapter 14.3)

Bile: A mixture secreted by the liver to accomplish the emulsification of lipids in the small intestine. (Chapter 14.3)

Bile duct: The tube that transports bile from the liver and gallbladder to the duodenum. (Chapter 14.3)

Bilirubin: The main bile pigment that is a waste product produced when the spleen removes old or damaged red blood cells from the circulation. (Chapter 14.3)

Bolus: Mass of chewed food. (Chapter 14.2)

Cardia: The point where the esophagus connects to and through which food passes into the stomach. (Chapter 14.3)

Catabolism: The breakdown of large molecules into smaller ones. (Chapter 14.4)

Cecum: A pouch-like structure about 2.4 inches long, located below the ileocecal valve, which receives contents from the ileum and continues absorption of water and salts. (Chapter 14.3)

Celiac disease: An inherited autoimmune disorder that causes the immune system to produce antibodies against the gluten protein. (Chapter 14.5)

Cementum: A layer of modified bone that covers the dentin of a tooth. (Chapter 14.3)

Chemical digestion: The process by which enzymes and acids break down food molecules into their chemical building blocks. (Chapter 14.2)

Cholelithiasis: Medical condition of having gallstones. (Chapter 14.5)

Chyme: Acidic “soup.” (Chapter 14.2, Chapter 14.3)

Circular folds: Deep ridges in the mucosa and submucosa that facilitate absorption. (Chapter 14.3)

Cirrhosis: Advanced scarring of the liver commonly caused by hepatitis or alcoholism. (Chapter 14.5)

Colectomy: A surgical procedure involving the removal of all or part of the colon. (Chapter 14.3)

Constipation: A condition characterized by infrequent, difficult, or painful bowel movements, often caused by slow movement of stool through the colon. (Chapter 14.3)

Crohn’s disease: A type of inflammatory bowel disease (IBD) that causes swelling and irritation of the tissues in the digestive tract. (Chapter 14.5)

Cuspids (canines): Teeth located next to the incisors with pointed edges designed to tear and pierce tough or fleshy foods. (Chapter 14.3)

Deciduous teeth: Primary or baby teeth. (Chapter 14.3)

Defecation: Final step in digestion as undigested materials are removed from the body as feces. (Chapter 14.2)

Deglutition: Another word for swallowing—the movement of food from the mouth to the stomach. (Chapter 14.3)

Dentes: Organs similar to bones that are used to tear, grind, and otherwise mechanically break down food. (Chapter 14.3)

Diarrhea: A condition in which waste moves too quickly through the intestines, preventing adequate water absorption and resulting in loose, watery stools. (Chapter 14.3, Chapter 14.5)

Diverticulitis: A condition in which diverticula become inflamed, often suddenly, and may lead to serious complications. (Chapter 14.5)

Diverticulosis: A condition that occurs when small pouches, or sacs, form and push outward through weak spots in the wall of the colon. (Chapter 14.5)

Duodenum: The shortest part of the small intestine. (Chapter 14.3)

Emulsification: The process where large fat globules are broken down into smaller droplets, increasing their surface area for easier digestion by enzymes. (Chapter 14.3)

Epiglottis: A flap of cartilage that closes over the windpipe during swallowing to prevent food and liquids from entering the airway. (Chapter 14.3)

Epiploic appendages: Small, fat-filled sacs of visceral peritoneum attached to the teniae coli of the colon. (Chapter 14.3)

Esophageal hiatus: An opening in the diaphragm through which the esophagus passes to connect to the stomach. (Chapter 14.3)

Esophagus: A muscular tube that connects the pharynx to the stomach. (Chapter 14.3)

Fat-soluble vitamins: Vitamins A, D, E, and K that are absorbed into the lymphatic system through the intestinal tract.  (Chapter 14.4)

Feces: Composed of undigested food residues, unabsorbed digested substances, millions of bacteria, old epithelial cells from the GI mucosa, inorganic salts, and enough water to let it pass smoothly out of the body. (Chapter 14.3)

Fundus: The dome-shaped upper part of the stomach, positioned below the diaphragm and above and to the left of the cardia. (Chapter 14.3)

Fungiform papillae: Mushroom shaped and cover a large area of the tongue.  (Chapter 14.3)

Gallbladder: A small, 3–4-inch-long organ located on the posterior side of the liver’s right lobe that stores and concentrates bile. (Chapter 14.3)

Gastric emptying: The process by which stomach contents gradually pass into the small intestine. (Chapter 14.3)

Gastroenteritis: An inflammation of the lining of the stomach and intestines. (Chapter 14.5)

Gastroenterologist: A physician who specializes in the diagnosis and treatment of gastrointestinal disorders. (Chapter 14.6)

Gastroenterology: The study of the normal function and diseases of the gastrointestinal (GI) system, also called the digestive system, including the esophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, bile ducts, and liver. (Chapter 14.1)

Gastroesophageal reflux disease (GERD): A chronic condition where stomach acid flows backward into the esophagus, causing irritation and heartburn. (Chapter 14.3, Chapter 14.5)

Gastrointestinal tract: A continuous tube from the mouth to the anus responsible for digestion, absorption of nutrients, and elimination of waste. (Chapter 14.1)

Gingivae: Soft tissues that line the alveolar processes and surround the necks of the teeth. (Chapter 14.3)

Glottis: The opening to the larynx. (Chapter 14.3)

Goblet cells: Secrete mucus and fluid into the lumen. (Chapter 14.3)

Hard palate: The bony, anterior part of the palate that provides a rigid floor for the nasal cavity and a surface against which the tongue can press food during chewing. (Chapter 14.3)

Haustra: Pouches formed by the contraction of the teniae coli that give the colon its wrinkled appearance and aid in the movement of fecal material. (Chapter 14.3)

Hemorrhoids: Swollen veins in the anus and lower rectum; also called piles. (Chapter 14.5)

Hepatic portal vein: Delivers nutrient-rich, partially deoxygenated blood from the small intestine to the liver, supplying more oxygen to the liver than the smaller hepatic arteries. (Chapter 14.3)

Hepatic sinusoid: An open, porous blood space formed by fenestrated capillaries from nutrient-rich hepatic portal veins and oxygen-rich hepatic arteries. (Chapter 14.3)

Hepatitis: Inflammation of the liver. (Chapter 14.5)

Hepatocyte: The liver’s main cell type, comprising about 80% of its volume, responsible for diverse secretory, metabolic, and endocrine functions. (Chapter 14.3)

Hepatopancreatic ampulla: A dilated chamber where the pancreatic duct and common bile duct merge and empty their secretions into the duodenum. (Chapter 14.3)

Hepatopancreatic sphincter: Regulates the flow of both bile and pancreatic juice from the ampulla into the duodenum. (Chapter 14.3)

Ileocecal valve: Located at the opening between the ileum and the large intestine; regulates the flow of chyme from the small intestine to the large intestine. (Chapter 14.3)

Ileum: The longest part of the small intestine, measuring about six feet in length. (Chapter 14.3)

Incisors: The sharp front teeth used for biting into food. (Chapter 14.3)

Ingestion: Eating or bringing food into the GI tract through the mouth. (Chapter 14.2)

Irritable bowel syndrome (IBS): A group of gastrointestinal symptoms that include changes in bowel movements, such as chronic diarrhea, constipation, or both. (Chapter 14.5)

Jaundice: Yellowing of the skin and eyes due to excess bilirubin. (Chapter 14.5)

Jejunum: The middle section of the small intestine, approximately three feet long, connecting the duodenum to the ileum. (Chapter 14.3)

Lactose intolerance: A condition characterized by an inability to digest lactose, the sugar found in dairy products. (Chapter 14.5)

Lamina propria: A layer of loose connective tissue within the mucosa that contains blood vessels, lymphatic vessels, and immune cells to support nutrient absorption and immune defense. (Chapter 14.3)

Laryngopharynx: The lower part of the throat that directs air to the voice box and food to the swallowing tube, serving as a pathway for both respiration and digestion. (Chapter 14.3)

Lingual lipase: An enzyme released from the glands of the tongue. (Chapter 14.3)

Liver: The largest internal organ in the body, weighing about three pounds in an adult. (Chapter 14.3)

Lower esophageal sphincter (LES): Relaxes to let food pass into the stomach and then contracts to prevent stomach acid from backing up into the esophagus. (Chapter 14.3)

Macronutrients: Carbohydrates, lipids, and proteins. (Chapter 14.4)

Mastication: Chewing. (Chapter 1.4.2)

Mechanical digestion: A physical process that does not change the chemical nature of the food but makes it smaller to increase surface area and mobility. (Chapter 14.2)

Metabolism: The sum of all the chemical reactions that occur in the body. (Chapter 14.4)

Micronutrients: Nutrients that are needed by the body in small amounts and include vitamins and minerals. (Chapter 14.4)

Minerals: Inorganic compounds that work with other nutrients to ensure the body functions properly. (Chapter 14.4)

Molars: Large teeth located at the back of the mouth with broad, flat surfaces designed for grinding and chewing food thoroughly. (Chapter 14.3)

Mucosa: The innermost layer of the gastrointestinal tract that secretes mucus and absorbs nutrients. (Chapter 14.2, Chapter 14.3)

Muscular diaphragm: Helps close the sphincter when no food is being swallowed. (Chapter 14.3)

Muscularis: A layer of the gastrointestinal tract composed of smooth muscle responsible for peristalsis and segmentation, typically organized into an inner circular layer and an outer longitudinal layer. (Chapter 14.3)

Muscularis mucosae: A thin layer of smooth muscle within the mucosa that helps move the mucosal surface to enhance secretion and absorption. (Chapter 14.3)

Nasopharynx: The upper section of the throat behind the nasal cavity that allows air to pass from the nose to the lungs. (Chapter 14.3)

Nutrient: A substance in foods and beverages essential for energy, growth, and tissue maintenance and repair, classified as water, macronutrients (carbohydrates, lipids, proteins), and micronutrients (vitamins and minerals). (Chapter 14.4)

Oropharynx: The middle section of the throat located behind the mouth that serves as a passageway for both food and air. (Chapter 14.3)

Overnutrition: Occurs in people who eat too much, eat the wrong things, don’t exercise enough, or take too many vitamins or other dietary replacements. (Chapter 14.5)

Palate: The arched shape of the palate allows chewing and breathing to occur simultaneously by separating the oral and nasal cavities, supporting both digestion and respiration. (Chapter 14.3)

Pancreas: A long, thin organ located mostly behind the lower part of the stomach that produces hormones and digestive enzymes. (Chapter 14.3)

Pancreatic duct: The channel that carries pancreatic juice from the pancreas to the duodenum. (Chapter 14.3)

Pancreatic islets: Clusters of endocrine cells in the pancreas that produce hormones such as insulin and glucagon to regulate blood glucose levels. (Chapter 14.3)

Pancreatic juice: A digestive fluid produced by the pancreas containing enzymes and bicarbonate that aid in digestion and neutralize stomach acid. (Chapter 14.3)

Papillae: Small, raised structures on the tongue’s surface that contain taste buds and help with food manipulation. (Chapter 14.3)

Parotid glands: The largest salivary glands located near the ears that secrete a watery saliva rich in enzymes to begin starch digestion. (Chapter 14.3)

Peptic ulcer: An open sore or raw area in the lining of the stomach or intestine. (Chapter 14.5)

Peristalsis: Involuntary, alternating wave-like contraction and relaxation of smooth muscles. (Chapter 14.2)

Peritoneum: The serous membrane that surrounds several organs in the abdominopelvic cavity, reducing friction between the organs and the abdominal wall. (Chapter 14.3)

Peritoneal cavity: Space between the visceral and parietal peritoneal layers. (Chapter 14.3)

Peritoneal fluid: Acts as a lubricant to minimize friction between the layers of the peritoneum. (Chapter 14.3)

Peritonitis: Inflammation of the peritoneum. (Chapter 14.5)

Pharynx (throat): Involved in both digestion and respiration, receiving food and air from the mouth and air from the nasal cavity. (Chapter 14.3)

Premolars: Teeth located behind the cuspids that have broad, flat surfaces for crushing and grinding food. (Chapter 14.3)

Propulsion: The movement of food through the digestive tract. (Chapter 14.2)

Pylorus: The narrow, funnel-shaped lower end of the stomach that connects to the small intestine. (Chapter 14.3)

Rectum: The final eight inches of the gastrointestinal tract. (Chapter 14.3)

Retroperitoneal: Refers to organs located behind the peritoneum, the lining of the abdominal cavity, meaning they lie between the peritoneum and the posterior abdominal wall. (Chapter 14.3)

Root: The part of the tooth that is embedded within sockets of the maxilla and mandible. (Chapter 14.3)

Rugae: Large folds in the mucosa and submucosa that form in the absence of food in the stomach. (Chapter 14.3)

Saliva: Composed mostly of water (99.4%), with the remaining 0.6% containing ions, glycoproteins, enzymes, growth factors, and waste products, where the key digestive enzyme is salivary amylase. (Chapter 14.3)

Salivary amylase: An enzyme in saliva that begins the chemical digestion of starches by breaking them down into simpler sugars. (Chapter 14.3)

Salivary glands: Exocrine structures in the mouth and tongue that continuously secrete saliva, aiding in digestion and oral hygiene. (Chapter 14.3)

Segmentation: Occurs mainly in the small intestine; consists of localized contractions of smooth muscle wall. (Chapter 14.2)

Serosa: The outermost layer of the alimentary canal, superficial to the muscularis, consisting of a thin layer of connective tissue and a layer of simple squamous epithelium. (Chapter 14.3)

Soft palate: The muscular, flexible posterior part of the palate that closes off the nasal passages during swallowing and speech. (Chapter 14.3)

Sphincters: Circular muscles that encircle and control the opening of various passages in the body. (Chapter 14.3)

Sublingual glands: Smallest salivary glands located beneath the tongue that produce mostly mucus-rich saliva to lubricate the mouth and food. (Chapter 14.3)

Submandibular glands: Salivary glands located beneath the lower jaw that produce a mixture of serous (watery) and mucus saliva to aid in digestion and oral lubrication. (Chapter 14.3)

Submucosa: A layer of dense connective tissue beneath the mucosa that contains blood vessels, lymphatics, and nerves, providing support and nourishment to the surrounding tissues. (Chapter 14.3)

Teniae coli: Three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. (Chapter 14.3)

Tongue: The strongest muscle in the body. (Chapter 14.3)

Tooth decay: Mechanical and chemical erosion of tooth enamel. (Chapter 14.3)

Ulcerative colitis: A type of inflammatory bowel disease (IBD) that causes inflammation and sores, called ulcers, in part of the digestive tract. (Chapter 14.5)

Undernutrition: Occurs when not enough essential nutrients are consumed or when they are excreted more rapidly than they can be replaced. (Chapter 14.5)

Upper esophageal sphincter (UES): Controls the movement of food from the pharynx into the esophagus. (Chapter 14.3)

Uvula: The small, conical projection that hangs from the posterior edge of the soft palate and helps prevent food from entering the nasal cavity during swallowing. (Chapter 14.3)

Valsalva’s maneuver: A voluntary process of contracting your diaphragm and abdominal wall muscles and closing your glottis to aid in defecation. (Chapter 14.3)

Vitamin B12: Necessary for both the production of mature red blood cells and normal neurological functioning. (Chapter 14.3)

Vitamins: Organic compounds found in foods and are a necessary part of the biochemical reactions in the body. (Chapter 14.4)

Water-soluble vitamins: Include vitamin C and the eight B vitamins that are absorbed with water in the gastrointestinal tract. (Chapter 14.4)