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BIOL 1142 Quiz 4

digestion, metabolism, reproductive system

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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