Key terms
74 terms- Herbivore§46.1
- Animal that eats plants exclusively
- Carnivore§46.1
- Animal that eats other animals
- Omnivore§46.1
- Animal that eats both plants and animals
- Gastrovascular cavity§46.1
- Digestive cavity with a single opening serving as both mouth and anus
- Alimentary canal§46.1
- One-way digestive tract with separate mouth and anus, allowing specialization
- Absorption§46.1
- Passage of digestion products through gut epithelium into the blood
- Mucosa / submucosa / muscularis / serosa§46.1
- The four tissue layers of the GI tract, lumen outward
- Gizzard§46.2
- Muscular chamber where swallowed pebbles grind food (birds, earthworms)
- Crop§46.2
- Storage pouch of the bird digestive tract
- Mastication§46.2
- Chewing — breaking food into small particles and mixing with secretions
- Incisors§46.2
- Chisel-shaped front teeth used for biting
- Canines§46.2
- Sharp pointed teeth used for tearing
- Premolars and molars§46.2
- Flattened ridged teeth for grinding and crushing
- Salivary amylase§46.2
- Enzyme in saliva that begins starch breakdown into maltose
- Soft palate§46.3
- Elevates during swallowing to seal off the nasal cavity
- Epiglottis§46.3
- Tissue flap that seals the glottis so food does not enter the trachea
- Swallowing reflex§46.3
- Involuntary response triggered by pressure on the pharynx; cannot be stopped
- Bolus§46.3
- Processed lump of food propelled down the esophagus
- Peristalsis§46.3
- Rhythmic one-directional waves of muscular contraction
- Sphincter§46.3
- Ring of circular smooth muscle controlling passage
- Gastric juice§46.3
- Acidic secretion of the tubular gastric glands
- Parietal cells§46.3
- Gastric gland cells that secrete HCl and intrinsic factor
- Chief cells§46.3
- Gastric gland cells that secrete pepsinogen
- Pepsinogen§46.3
- Inactive pepsin precursor; 44 extra amino acids block its active site
- Pepsin§46.3
- Active stomach protease that cuts proteins into shorter polypeptides
- Intrinsic factor§46.3
- Parietal cell polypeptide required to absorb vitamin B12
- Pernicious anemia§46.3
- Low red blood cell count from insufficient intrinsic factor
- Chyme§46.3
- Mixture of partially digested food and gastric juice
- Peptic ulcer§46.3
- Hole eaten through the stomach or duodenal wall by acid
- Helicobacter pylori§46.3
- Bacterium that is the most common cause of peptic ulcers
- Pyloric sphincter§46.3
- Muscular ring controlling chyme exit from stomach into duodenum
- Duodenum§46.4
- First 25 cm of the small intestine; receives pancreatic juice and bile
- Jejunum§46.4
- Middle region of the small intestine
- Ileum§46.4
- Final region of the small intestine
- Villi§46.4
- Fingerlike projections of the intestinal wall that increase surface area
- Microvilli§46.4
- Membrane foldings on the apical surface of villus cells
- Brush border§46.4
- The microvilli-covered epithelial wall, carrying membrane-bound enzymes
- Lactase / lactose intolerance§46.4
- Brush border enzyme for milk sugar; many adults lose it
- Hepatic portal vein§46.4
- Vein carrying absorbed nutrients from intestine directly to the liver
- Chylomicron§46.4
- Protein-coated triglyceride particle that enters lymphatic capillaries
- Colon§46.4
- Large intestine — absorbs water and electrolytes; no villi, no digestion
- Cecum§46.4
- Pouch at the small/large intestine junction; enlarged in hindgut fermenters
- Appendix§46.4
- Vestigial structure extending from the cecum
- Acini§46.5
- Clusters of pancreatic secretory cells making enzymes and bicarbonate
- Zymogen§46.5
- Inactive enzyme precursor, activated only where it is needed
- Trypsinogen → trypsin§46.5
- Pancreatic zymogen cut by enterokinase into active protease
- Enterokinase§46.5
- Brush border enzyme that activates trypsinogen
- Islets of Langerhans§46.5
- Endocrine cell clusters in the pancreas: β cells → insulin, α cells → glucagon
- Bile§46.5
- Liver secretion of bile pigments (waste) and bile salts (digestive)
- Bile salts§46.5
- Detergent-like molecules that emulsify fat
- Emulsification§46.5
- Dispersal of large fat drops into fine droplets, raising surface area for lipase
- Jaundice§46.5
- Yellow tissue staining from accumulated bile pigments
- Cirrhosis§46.5
- Liver scarring, classically from chronic alcohol abuse
- Edema§46.5
- Fluid accumulation in tissues when plasma protein concentration falls
- Glycogenolysis§46.5
- Breakdown of glycogen to glucose 6-phosphate
- Gluconeogenesis§46.5
- Making new glucose from amino acids and lactic acid
- Gastrin§46.6
- Stomach hormone triggered by protein; drives HCl and pepsinogen secretion
- Enterogastrones§46.6
- Duodenal hormones (CCK, secretin, GIP) that inhibit gastric activity
- Cholecystokinin (CCK)§46.6
- Fat-triggered hormone: gallbladder contraction + pancreatic enzymes
- Secretin§46.6
- Acid-triggered hormone: pancreatic bicarbonate. First hormone ever discovered
- Gastric inhibitory peptide (GIP)§46.6
- Fat-triggered hormone that inhibits stomach emptying
- Basal metabolic rate (BMR)§46.7
- Minimum energy consumption under defined resting conditions
- Kilocalorie§46.7
- 1000 calories; the nutritionists' capital-C "Calorie"
- Leptin§46.7
- Adipose hormone, the main long-term satiety signal; encoded by the ob gene
- Ghrelin§46.7
- Gut hormone that stimulates feeding; rises before meals
- Neuropeptide Y (NPY)§46.7
- Hypothalamic peptide that induces feeding
- α-MSH§46.7
- Hypothalamic peptide that suppresses feeding
- Essential nutrients§46.7
- Substances required in the diet because the body cannot make them
- Ruminant§46.8
- Herbivore with a four-chambered stomach (cow, deer)
- Rumen§46.8
- Large fermentation chamber, up to 50 gallons
- Abomasum§46.8
- The true stomach of a ruminant — the only chamber secreting gastric juice
- Rumination§46.8
- Regurgitating and rechewing rumen contents — "chewing the cud"
- Coprophagy§46.8
- Eating nutrient-rich feces to pass food through the tract a second time
- Lysozyme§46.8
- Antibacterial enzyme repurposed to digest stomach bacteria in ruminants and langurs