STUDY GUIDE FOR CHAPTER 14
In addition to the
definitions below, please also review class handouts.
Mouth (oral
cavity) - portion of the digestive tract, containing teeth and tongue, in
which food is chewed by the teeth and moistened with saliva. The mouth is derived from the stomodeum in
the embryo.
Hard palate - hard, bony portion of the roof of the mouth.
Soft palate - the more flexible portion of the roof of the mouth posterior to the hard palate.
Saliva - watery fluid that moistens food, contains a starch-digesting enzyme, and is secreted by salivary glands.
Alimentary canal or tract - a tube made up of the hollow organs of the digestive system.
Gut - that portion of the alimentary canal that is lined with endoderm, from the esophagus to the rectum.
Esophagus - simple, tube-like portion of the gut between the mouth and stomach.
Mucosa - innermost epithelial layer of any portion of the alimentary canal.
Submucosa - tissue layer surrounding the mucosa, consisting largely of connective tissue.
Muscularis externa - muscular portion of the lining of the alimantary canal, usually consisting of two layers (circular and longitudinal), but also containing an additional (oblique) layer in the stomach.
Serosa - outermost layer of the alimentary tract, continuous with the visceral peritoneum.
Coelom - the body cavity, lined everywhere with mesoderm
Peritoneum - the mesodermal lining of any part of the coelom, including the parietal peritoneum along the outer walls and the visceral peritoneum that adheres to the abdominal organs.
Abdominal cavity - the portion of the body cavity (coelom) lying caudal to the diaphragm.
Mesentery - a sheetlike structure composed of two layers of visceral peritoneum.
Greater omentum - an expansion of the mesentery into an apron-like structure that covers the intestines.
Omental bursa - the pouch or cavity between layers of the greater omentum.
Stomach - an expanded portion of the digestive tract in which protein digestion takes place.
Liver - a very large, multi-lobed organ that secretes bile and stores excess sugars in the form of glycogen.
Gall bladder - a small pouch that stores bile secreted by the liver.
Pancreas - a glandular organ that secretes many digestive enzymes and also produces insulin.
Small intestine - the small-diameter portion of the intestine, including duodenum, jejunum, and ileum.
Duodenum - the first, relatively short portion of the small intestine, receiving the secretions of the liver and pancreas
Jejunum - the longest portion of the small intestine (about 2/3 of everything after the duodenum), in which chemical digestion is completed.
Ileum - the last portion of the small intestine (about 1/3 of its length), given mainly to food absorption.
Villi - finger-like processes that increase the surface area for absorption in the ileum.
Large intestine - the large-diameter portion of the intestine, including caecum, colon, and rectum.
Caecum - a dead-end portion of the large intestine, containing many bacteria. Cellulose digestion occurs in the caecum of many herbivores (rabbits, horses, etc.) but not in humans.
Appendix (or vermiform appendix) - a small bacterial culture chamber attached to the caecum.
Colon - the longest portion of the large intestinem, given mainly to the absorption of water. It consists of an ascending colon, a transverse colon, a descending colon, and a sigmoid (S-shaped) colon.
Left colic (splenic) flexure - the bend between the transverse and descending parts of the colon. Many blood vessels and nerves extend to this flexure from both sides, but do not cross it.
Rectum - the straight, terminal portion of the large intestine.
Anus - the exit from the rectum, derived from the proctodeum (and thus not technically part of the gut).
Nutrients - food ingredients that nourish the body.
Macronutrients - nutrients (carbohydrates, fats, proteins) responsible for most of our calories.
Kilocalorie - the amount of food energy needed to raise the temperature of 1 kilogram of water by 1oC. NOTE: “calories” on food labels or in diets are really kilocalories.
Carbohydrates - nutrients made of sugar units, containing carbon, hydrogen, and oxygen.
Starch - a polymer made of multiple units of glucose.
Disaccharide - a double sugar, containing two sugar units linked together. Common double sugars include maltose (derived from starch, containing two glucose units), sucrose (table sugar, composed of glucose + fructose), and lactose (the sugar in milk, composed of glucose + galactose).
Monosaccharide - a single sugar, such as glucose, fructose, or galactose.
Glucose - C6H12O6, the most common sugar inside cells or in the bloodstream.
Fructose - also C6H12O6, the sugar in grapes and most other fruits.
Lipids - hydrophobic (water-insoluble) molecules with a higher H to O ratio than carbohydrates. The most common dietary lipids are triglycerides, which combine glycerol and three fatty acid units. Triglycerides are usually called fats if solid and oils if liquid at room temperature.
Amino acids - molecules containing both an acid group -COOH and an amino group -NH2 .
Protein - a polymer containing one or more chains of amino acids linked together.
Peptide - a small protein fragment.
Enzyme - an organic catalyst, something that speeds up a chemical reaction without getting used up in the process. Digestive enzymes are usually named after what they break down, with the ending “-ase”:
Amylase - digests starch into maltose Protease - digests proteins into peptides
Lactase - digests lactose into glucose + galactose Sucrase - digests sucrose into glucose +fructose
Peptidase - digests peptides, removing one amino acid at a time
Lipase - digests lipids (triglycerides) into glycerol + 3 fatty acids
Bile - the secretion of the liver, containing bile salts, soap-like molecules with both water-soluble (hydrophilic) and water-insoluble (hydrophobic) portions.
Emulsification - the process of coating small lipid droplets with soap-like molecules (such as bile salts), preventing them from blending into larger droplets, thus keeping their surface area very high.
Fiber - indigestible material that passes through the alimentary canal chemically unaltered.
Vitamin - an organic nutrient needed in very small quantity only, usually functioning as part of an enzyme.
Mineral - an inorganic nutrient, such as a metallic ion, needed in small quantity only.
Kwashiorkor - a type of starvation that also includes protein deficiency.
Anorexia nervosa - type of starvation resulting from a relentless pursuit of thinness, usually by women.
Diabetes mellitus - metabolic disease resulting in high and inconstant blood sugar. Type I diabetes is the result of too little insulin. Type II diabetes results from receptor cells that do not respond to insulin.
Body Mass Index (BMI) - weight (in kilograms) divided by the square of height (in meters).
Obese - having a body mass index of 30 or above.
Overweight - having a body mass index of 25 or above.
Gastric ulcers - lesions of the stomach lining, usually caused by Helicobacter pylori.
Basal metabolic rate - the body’s energy requirements when awake, relaxed, and lying down.
Chyme - liquefied food in the stomach.
Feces (stools) - waste materials exiting the body via the anus.
Lacteals - lymph vessels in the ileum that absorb lipids and carry them ultimately to the thoracic duct.
Heat stroke - a condition of severe dehydration and uncontrollably rising temperature, fatal if untreated.
Heat exhaustion - collapse from dehydration, but with heat-loss mechanisms still intact; give fluids.
Peristalsis - smooth muscle contraction that moves food through the alimentary canal.