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BIOL 1142 Quiz 4
digestion, metabolism, reproductive system
| Question | Answer |
|---|---|
| 4 basic processes of digestion | motility, secretion, digestion, absorption |
| motility | movement of material through the GI tract/alimentary canal; aka mechanical digestion |
| secretion | happens throughout digestion when organs secrete different hormones, paracrines, etc. |
| digestion | breaking bonds; enzymatic process that breaks lipids, proteins and carbohydrates into smaller parts |
| absorption | takes place almost completely in the small intestine, where nutrients enter the bloodstream |
| saliva | 99.5% water, also contains electrolytes and protein |
| functions of saliva | moistening and lubricating food, antibacterial actions, solvent for tastants, aids speech |
| amount of saliva produced each day | 1-2 L, continuous flow of .5 mL/min due to tonic parasympathetic activation |
| simple salivary reflex | chemoreceptors and pressure sensors respond to food; salivary center is located in the medulla |
| conditioned salivary reflex | salivary center is activated by thinking, seeing, smelling and/or hearing food |
| oral cavity function during digestion | secretion (saliva, amylase), motility (moves food to the esophagus for transport to the stomach, intestines) |
| amylase | enzyme that begins carbohydrate digestion - breaks them into disaccharides; improves taste and begins chemical digestion |
| factors that affect gastric emptying | 1. duodenal fat, acid, hypertonicity, and distention (usually these are inhibitory) 2. amount of chyme in the stomach |
| vomiting | controlled by vomit center in the medulla; begins with deep inhalation and closure of the glottis; relaxation of stomach and esphagus, contraction of diaphragm and abdominals |
| functions of the stomach during digestion | motility (regulates movement of material into the small intestine), secretion (HCl, gastrin, mucus, pepsinogen, intrinsic factor) |
| gastrin | hormone that stimulates secretion of HCl |
| amount of secretions from the stomach each day | 2 L/day |
| stomach - cells that secrete | mucus cells - mucus, chief cells - pepsinogen, parietal cells - HCl and intrinsic factor |
| function of HCl | activates pepsinogen, optimizes pepsin activity; aids in connective tissue breakdown; denatures proteins; kills most microorganisms |
| pH of the stomach | 1-2 |
| intrinsic factor | binds to B12, required for absorption of B12 in the small intestine |
| pepsinogen | precursor enzyme that becomes actives when exposed to pH of 2. |
| protease | begins breakdown of proteins into smaller peptide chains |
| hormones/neurotransmitters that influence parietal and chief cell activity in the stomach | acetylcholine, gastrin, histamine, somatostatin |
| 3 phases of digestion | cephalic (stimulated by food), gastric (stimulated by internal environment of the stomach), intestinal (stimulated by the small intestine) |
| histamine | paracrine that stimulates secretion |
| somatostatin | inhibitory hormone; suppresses, slows down digestive activity |
| absorption in the stomach | alcohol (slow) and aspirin are absorbed, no food is absorbed here |
| pancreatic secretions | exocrine (pancreatic juice) and endocrine (insulin); regulated during the intestinal phase of digestion |
| pancreatic lipase | breaks down lipids, only source is the pancreas |
| acinar cells | produce pancreatic enzymes (proteolytic enzyme, pancreatic amylase, pancreatic lipase) |
| duct cells | produce aqueous alkaline solution (mucus) that is bicarbonate-rich |
| secretin | hormone released by the pancreas in response to acid |
| cholecystokinin (CCK) | released by the pancreas in response to fat |
| 3 sources of bicarbonate that will raise the PH of the digestive tract | duodenum, pancreas, liver (bile) |
| liver secretions | bile - bile salts, cholesterol, bilirubin, aqueous alkaline fluid |
| bilirubin | waste product from breakdown of red blood cells; turns feces green and urine yellow |
| bile salts | required for fat digestion; emulsify fats; are "recycled" via enterohepatic circulation; need 15 g after a big meal, usually only 3-4 g of bile salts are out at a time |
| segmentation | occurs during a meal; mixes and slowly propels; controlled by intestinal pacemaker cells |
| migrating motility complex | intestinal housekeeper; weak persistent waves that move what is left in the intestines right along; contractions break down food, increasing surface area (segmantation); prevents backup of microorganisms |
| small intestine secretion | succus entericus, digestive enzymes (enterokinase, disaccharidases, aminopeptidases) |
| succus entericus | aqueous salt/mucus solution that lubricates and protects the small intestine; contains water needed for hydrolytic digestive reactions, does not include enzymes; about 1/5 L /day secreted |
| enterokinase | activates pancreatic trypsin, breaks down peptides into individual amino acids |
| disaccharidases | sucrase, maltase, lactase |
| 3 anatomical features that greatly increase surface area of small intestine | folds, villi, microvilli |
| energy dependent Na+ absorption in the small intestine | apical - symport with Cl-, glucose or amino acid; antiport with H; basal - Na/K pump (requires ATP), located in lateral space creates high osmolarity which drives water absorption |
| carbohydrate and protein absorption in the small intestine | apical - occurs via Na+ dependent symport; basal - facilitated diffusion |
| fat digestion and absorption in the small intestine | large triglycerides are emulsified by bile salts; pancreatic lipase hydrolyzes triglycerides into monoglycerides and free fatty acids; form micelles; monoglycerides/fatty acids cross apical membrane; form chylomicrons; exocytosis -> central lacteals |
| micelles | monoglycerides and free fatty acids that combine with bile salts to aid in transport across apical membrane of the small intestine |
| chylomicrons | resynthesized triglycerides coated with lipoproteins for transport across basal membrane via exocytosis |
| central lacteal role in fat digestion | carries fats that are too large for the bloodstream |
| large intestine functions | motility, secretion, digestion, absorption |
| small intestine functions | motility, secretion, digestion, absorption |
| haustra | pouches in the large intestine that contract slowly and nonpropulsively; aid in water and electrolyte absorption |
| mass movement | occur 3-4 times per day, large portions of ascending/transverse colon contract, driving feces 1/3 to 3/4 the length of the colon over several seconds; controlled by the gastrocolic reflex (stimulated when gastrin is released when food enters the stomach) |
| large intestine secretions | entirely protective, alkaline mucus only, no digestive enzymes; lubricates and aids in passage of material |
| large intestine digestion | occurs by 500-1,000 different species of resident bacteria, vitamin K and glucose from cellulose are digested |
| vitamin K | necessary for the liver to produce certain plasma proteins |
| large intestine absorption | active transport of Na+, passive transport of Cl- and water follows osmotically |
| feces | 150 g per day; 100 g is water and 50 g is solid; of the solid feces, 1/3 is bacteria, 2/3 is undigestible substances |
| gastrointestinal hormones | gastrin, secretin, CCK, GIP |
| gastrin | released by the stomach when food is present; increases secretion of HCl and pepsinogen; enhances gastric motility, ileal motility, relaxes ileocecal junction, stimulates mass movements |
| secretin | activated by decrease in pH of small intestine; inhibits gastric emptying and secretion; stimulates pancreas and liver to secrete NaHCO3 |
| cholecystokinin (CCK) | stimulated by fat presence in small intestine; inhibits gastric motility and secretion; stimulates pancreatic enzyme secretion; activates contraction of the gall bladder, relaxation of sphincter of Oddi |
| sphincter of Oddi | where bile and pancreatic secretions enter the small intestine |
| Gastric Inhibitory Peptide (GIP) | glucose-dependent insulinotrophic peptide; stimulated by the presence of carbs in the small intestine, acts as a feedforward activator of insulin secretion |
Created by:
pinklrt98
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