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Biomed II Exam 4
Digestion System
| Question | Answer |
|---|---|
| what is ingestion? | taking food into the mouth |
| what is propulsion? | movement of substances through the GI tract swallowing and peristalsis |
| what is mechanical digestion? | mechanical breakdown of food and mixing food with digestive enzymes like chewing in the mouth, churning in stomach and segmentation in intestine |
| what is chemical digestion? | chemical breakdown of food into smaller molecules enzymatic digestion |
| what is absorption? | passage of digested products into epithelial cells lining the human of GI tract then into blood and lymph |
| what is defacation? | elimination of feces |
| what are the pharynx and esophagus used for? | transportation |
| what is the stomach for? | mechanical disruption, absorption of alcohol |
| what is the small intestine for? | chemical and mechanical digestion and absorption |
| what is the large intestine for? | absorb water, electrolytes and vitamins B and K |
| what are the layers of the GI tract? | mucosal layer, submucosal layer, muscularis layer, serosa layer |
| what is in the mucosal layer of the GI tract? | epithelium- stratified squamous, simple columnar lamina propria muscularis mucosae |
| what kind of tissue covers the mouth, esophagus and anus? | stratified squamous epithelium, tough |
| what is the stratified columnar epithelium in the mucosal layer of the GI tract used for? | secretes enzymes and absorbs nutrients, specialized cells (goblet) secrete mucous onto cell surface, enteroendocrine cells which secrete hormones controlling organ functions |
| what do enteroendocrine cells secrete? | hormones controlling organ functions |
| what is the lamina propria mucosal layer of the GI tract for? | thin layer of loose connective tissue contains blood vessels and lymphatic vessels |
| what is the muscular is mucosae of mucosal layer of the GI tract for? | causes folds to form in mucosal layer to increase surface area for digestion and absorption increases local movements increasing absorption with exposure to new nutrients |
| what is the loose connective tissue in submucosa for? | containing blood vessels, lymphatic vessels, glands and lymphatic tissue |
| what is the submucosal plexus of the submucosa layer for? | chemoreceptors detect certain chemicals in food located in the lumen of the GI organ stretch receptors detect the wall stretches of GI organ |
| what do the motor neurons in the submucosa layer do? | control the secretions of the organs of GI tract |
| what is contained in the muscularis layer? | skeletal muscle, smooth muscle and myenteric plexus |
| what does the skeletal muscle do in the muscularis layer? | voluntary control, contained in the mouth, pharynx, upper esophagus and anus control over swallowing and defecation |
| what does the smooth muscle do in the muscularis layer do? | involuntary control inner layer of circular fibers and outer layer of longitudinal fibers crushes, mixes and propels food forward by peristalsis |
| what does the myenteric plexus do in the muscularis layer? | motor neurons control GI tract motility the frequency and strength of contraction of muscularis |
| where is the myenteric plexus located in muscularis layer? | located between the longitudinal and circular smooth muscle layers of the muscularis |
| what are the two layers of the serosa? | parietal and visceral layer they secrete slippery fluids to lubricate adjacent layers |
| what is the parietal layer? | membrane lining the walls of cavity |
| what is the visceral layer? | membrane covering organs in cavity |
| what does the parasympathetic nerves do for the GI tract? | form neural connections with ENS stimulation of the parasympathetic nervous system INCREASES the secretion and motility of GI tract |
| what does the sympathetic nerves do for the GI tract? | form neural connections with ENS stimulation of the sympathetic nerves DECREASES the secretion and motility of the GI tract |
| what is a bolus? | a soft flexible easily swallowed mass |
| what are the chemical digestion in the mouth? | salivary amylase, lingual lipase |
| what does salivary amylase do? | secreted by salivary glands begins starch digestion at pH 6.5 or 7.0 found in mouth when bolus and enzyme hit the pH 2.5 gastric juices hydrolysis ceases |
| what does lingual lipase do? | secreted by lingual glands in the tongue activated by acids in the stomach begins breakdown of triglycerides |
| what is the esophagus? | collapsed muscular tube, muscularis has two sphincters |
| what is the upper 1/3 of the esophagus? | skeletal muscle, middle is mixed muscle |
| what is the lower 1/3 of the esophagus? | smooth muscle |
| what are the two sphincters of the esophagus? | upper esophageal sphincter- circular skeletal muscle lower esophageal sphincter- circular smooth muscle |
| what is the physiology of the esophagus? | secretes mucus- NO digestive enzymes transports food into the stomach, NO digestion or absorption happens |
| what is swallowing? | the passage of food from the mouth into the stomach involves mouth, pharynx and esophagus facilitated by secretion of saliva and mucus |
| what are the three stages of swallowing? | voluntary stage, pharyngeal stage, esophageal stage |
| what happens during the voluntary stage of swallowing? | the bolus is passed into the oropharynx |
| what happens during the pharyngeal stage of swallowing? | involuntary passage of the bolus through the pharynx into the esophagus |
| what happens during the esophageal stage of swallowing? | involuntary passage of the bolus through esophagus into stomach |
| what happens first when swallowing? | bolus moves into esophagus once the upper esophageal sphincter relaxes, peristalsis pushes the bolus down |
| what is the pyloric sphincter? | gateway between the stomach and duodenum empties as small squirts of chyme leave the stomach |
| what is the histology of the stomach | mucosa: simple columnar epithelium lamina propria muscularis mucosae |
| what do mucous neck cells secrete? | mucous to protect the lining of the stomach |
| what do chief cells secrete? | pepsinogen and gastric lipase |
| what do parietal cells secrete? | intrinsic factor- breaks down vitamin B 12 hydrochloric acid- converts pepsinogen to pepsin |
| what does the hydrochloric acid secreted by the parietal cells do? | converts inactive pepsinogen to pepsin |
| what do G cells or enteroendocrine cells secrete? | gastrin hormone, which stimulate gastric glands to secrete gastric juice, increase gastric motility, relax pyloric sphincter and constrict esophageal sphincter preventing entry |
| how does mechanical digestion happen in the stomach? | gentle mixing waves to more vigorous mixing waves to intense waves near pylorus |
| what happens in the stomach as far as chemical digestion? | protein digestion begins- HCL denatures and kills bacteria fat digestion continues- gastric lipase splits triglycerides |
| what are some nutrients that are absorbed in the stomach | electrolytes, short chain fatty acids, some drugs (aspirin), alcohol |
| what slows the passage of alcohol to the intestine in the stomach? | fat content in the stomach absorption is more rapid in the small intestine |
| what do gastric mucosal cells contain to help break down alcohol? | alcohol dehydrogenase converts alcohol to acetaldehyde |
| what are the three phases or gastric secretion and motility? | cephalic phase gastric phase intestinal phase |
| what happens during cephalic phase? | stomach getting ready cerebral cortex = sight, smell, initial taste and thought vagus nerve increase stomach muscle activity, stimulate gastric glands to secrete gastric juice |
| what happens during gastric phase? | stomach working phase stretch receptors detect dissension of stomach chemoreceptors monitor the pH of stomach chyme gastric glands secrete gastric juices vigorous peristalsis mixes food with gastric juices and forces chyme into duodenum |
| what are the stimuli causing G cells to secrete gastrin? | dissension of the stomach by chyme increased pH in gastric chyme caffeine or protein in gastric chyme acetylcholine released from parasympathetic neurons |
| what are the effects of G cells secreting gastrin? | stimulate gastric glands to secrete gastric juice increase gastric motility relaxes pyloric sphincter constrict esophageal sphincter preventing entry |
| what happens during intestinal phase? | stomach emptying stretch receptors detect dissension of duodenum chemoreceptors detect fatty acids and glucose in duodenum stimulate slowing of stomach activity |
| what is the hormonal regulation of the intestinal phase? | secreting hormone inhibits secretion of gastric juice cholecytokinin (CCK) slows gastric emptying by contracting the pyloric sphincter castric inhibitory peptide decreases stomach secretions motility and emptying |
| what are the neural and hormonal activities during gastric phase | stimulate gastric secretion increase gastric motility |
| what are the neural and hormonal reflexes during intestinal phase? | increase intestinal activity slow stomach activity |
| what is a enterogastric reflex? | dissension of duodenum and contents of chyme inhibits gastric motility and contract pyloric sphincter inhibition of gastric emptying |
| what is vomiting? | forceful expulsion of contents of stomach and duodenum through the mouth caused by irritation or dissension of stomach or unpleasant sight, general anesthesia, dizziness or certain drugs |
| what does the medulla do during vomiting | output nerve imupulses cause stomach contraction and complete sphincter relaxation stomach is squeezed between diaphragm and abdominal muscles and contents forced out through mouth |
| what are the two ducts of the pancreas? | pancreatic duct: main duct accessory duct |
| what does the pancreatic duct do? | joins common bile duct (from liver and gallbladder) to form a dilated common bile duct called hepatopancreatic ampulla |
| what is the hepatopancreatic ampulla | common bile duct and pancreatic duct joining |
| what is the sphincter of Oddi | mass of smooth muscle surrounding the ampulla controls the passage of pancreatic juices and bile |
| what makes up pancreatic juice? | water, sodium bicarbonate and enzymes |
| what does sodium bicarbonate do in pancreatic juice? | makes pancreatic juice alkaline neutralizes acidic gastric juice in chyme stops pepsin (from stomach) activity forms proper pH for digestive enzyme in small intestine |
| what are the digestive enzymes found in pancreatic juice? | pancreatic amylase: starch digestion pancreatic lipase: triglyceride digesting proteases: protein digesting enzymes ribonucleas/ deozyribonuclease |
| what are the proteases or protein digesting enzymes found in pancreatic juice? | trypsin, chymotrypsin, carboxypeptidase and elastase |
| what activates trypsinogen for protein breakdown | enterokinase (brush border enzyme) |
| what activates chymotrypsinogen for protein breakdown? | trypsin |
| what activates procarboxypeptidase and proelastase for protein breakdown? | trypsin |
| what does trypsin inhibitor do? | combines with any trypsin produced in the pancreas and blocks its enzymatic activity |
| what is pancreatitis? | inflammation of the pancreas occurring with alcohol abuse or chronic gallstones |
| what is acute pancreatitis? | associated with heavy alcohol intake or biliary tract obstruction patient secretes trypsin in pancreas and it starts to digest the pancreatic cells |
| what does secretin do and what activates it? | acidic chyme in intestine stimulates release of secretin secretin increases secretion of sodium bicarbonate |
| what does cholecystokinin do and what activities it? | fats and proteins stimulate secretion of CCK CCK increases secretion of digestive enzymes |
| what is the anatomy of the liver? | divided into a larger right lobe and a smaller left lobe by falciform ligament |
| what is the pathway of bile secretion | bile produced by hepatocytes, bile canaliculi, bile ductules, bile ducts, R/L hepatic ducts, common hepatic duct, joins cystic duct, common bile duct, joins pancreatic duct to be hepatopancreatic ampulla |
| common hepatic duct joins _____ from gallbladder to form... | cystic duct from gallbladder to form common bile duct |
| what makes up the hepatopancreatic ampulla? | common bile duct and pancreatic duct joining |
| what supplies blood to the liver? | hepatic artery: branches of aorta and supplies oxygenated blood hepatic portal vein: originates in GI tract and supplies deoxygenated but nutrient rich blood |
| what is the blood flow through the liver? | oxygenated blood from hepatic artery/ nutrient rich deoxygenated blood from hepatic portal vein liver sinusoids, central vein, hepatic vein, inferior vena cava, right atrium of heart |
| what is the pH of bile? | 7.6 to 8.6 |
| what is the components of bile? | water and cholesterol, bile salts K and Na, bile pigments bilirubin derived from hemoglobin |
| heme can be broken down into | iron and can be recycled bilirubin secreted into bile |
| what is emulsification | the breakdown of large lipid globule into several small lipid globules |
| what is the role of bile salts? | emulsification and absorption of lipids |
| if blood glucose is high what does the liver do? | converts glucose to glycogen and store in the liver |
| if blood glucose is low what does the liver do? | break down glycogen to glucose and release it into bloodstream convert amino acids and lactic acid into glucose convert fructose and galactose into glucose turn triglycerides into glucose |
| where does gastrin work? | stomach, gastric and ileocecal sphincters |
| where does gastric inhibitory peptide work? | stomach and pancreas |
| where does secretin work? | pancreas, liver and stomach |
| where does cholecytokinin CCK work? | pancreas, gallbladder, sphincter of Oddi and stomach |
| what are the three parts of the small intestine? | duodenum, jejunum, ileum |
| where does the duodenum being? | pyloric sphincter |
| where does the ileum end? | ileocecal sphincter |
| what are the structures that increase surface area of the small intestine? | circular folds or plic circularis villi, microvilli |
| what are circular folds or plica circularis | folds of the mucosa and submucosa begins at proximal portion of duodenum end at the mid portion of ileum |
| what are the villi? | fingerlike projections of mucosa cora is lamina propria of mucosa contain vascular capillaries and lacteals (lymphatic capillaries) |
| what are microvilli? | plasma membrane covered projections found on the apical surface of absorptive cells |
| what are the functions of microvilli? | digestion: enzymes absorption: absorbs nutrients from chyme |
| what cells make up the intestinal glands? | absorptive cells, goblet cells, enteroendocrine cells, paneth cells |
| what do absorptive cells do? | digest and absorb nutrients in small intestinal chyme |
| what do goblet cells do? | unicellular glands that secrete mucus |
| what do enteroendocrine cells do? | secrete hormones secretin, cholecystokinin and GIP |
| what do paneth cells do? | secrete lysozymes and carry out phagocytosis |
| what is intestinal juice? | a clear yellow fluid pH 7.6 contains water and mucus, helps absorb substance from chyme in small intestine |
| what does the duodenal glands do? | found in submucosa of duodenum secrete an alkaline mucus that neutralizes gastric aid in the chyme |
| what are the brush border enzymes? | carbohydrate digesting enzymes protein digesting enzymes nucleotide digesting enzymes |
| how are carbohydrates broken down? | mouth salivary amylase nothing in esophagus or stomach small intestine: pancreatic amylase digest starch and glycogen brush border enzymes break disaccharides into monosaccharides |
| what is lactose intolerance? | absorptive cells of small intestine fail to produce lactase, undigested lactose retains fluid in the feces and bacterial fermentation of undigested lactose produces gases |
| what are the symptoms of lactose intolerance? | diarrea, gas, bloating and abdominal cramps |
| how are proteins broken down? | stomach: HCL denatures, pepsin turns proteins into peptides small intestine: trypsin, chymotrypsin elastase cleave peptide bond catboxypeptidase: splits off amino acid at carboxyl end brush border: amino peptidase, dipeptidase |
| how are lipids broken down? | mouth- lingual lipase, NO DIGESTION stomach- gastric lipase small intestine: emulsification by bile salts, pancreatic lipase splits triglycerides into fatty acids and monoglycerides NO ENZYMES IN BRUSH BORDER |
| what nutrient is not broken down by enzymes in the brush border? | lipids |
| how are nucleic acids broken down? | pancreatic juice contains 2 nucleases: ribonuclease, deoxyribonucleas nucleotides further broken down by brush border enzymes |
| what do enteric reflexes do when responding to the presence of chyme? | increase intestinal mobility vasoactive intestinal polypeptide: stimulates production of intestinal juices segmentation depends on distention |
| how are glucose and galactose absorbed in the small intestine? | secondary active transport with Na+ (outside to in) facilitated diffusion to blood (once inside) |
| how is fructose absorbed in the small intestine? | facilitated diffusion |
| how is amino acids absorbed in the stomach? | active transport or secondary active transport with Na+ inside cells diffusion |
| how are dipeptides and tripeptides absorbed in the small intestine? | secondary active transport with H+into the cell diffusion once inside the cell |
| how are short chain fatty acids absorbed in the small intestine? | simple diffusion inside the cell diffusion once inside the cell |
| how are long chain fatty acids and monoglycerides absorbed in the small intestine? | simple diffusion inside the cell with micelle triglycerides form and get into chylomicron and transport through lymphatics |
| what is the only nutrient that is not absorbed by the blood | triglycerides in chylomicron goes to lymphatics |
| what are micelles made from? | bile salts in intestinal chyme |
| what nutrients need a micelle to be absorbed | large fatty acids, monoglycerides, fat soluble vitamins (A, D, E, K) cholesterol |
| what is enteroheptic circulation? | bile salts are reabsorbed into blood in the ileum returned to the liver through the hepatic portal system and desecrated into bile by the liver |
| what are sources of elecytolytes? | GI secretion and ingested foods and liquids |
| how are sodium and potassium entering epithelial cells? | diffusion and secondary active transport |
| how are chloride, iodide and nitrate ions entering epithelial cells | passively follow Na+ |
| how are iron, magnesium and phosphate ions entering epithelial cells? | active transport |
| how are Ca2+ entering epithelial cells? | active transport that requires vitamin D and parathyroid hormone |
| how are fat soluble vitamins (A, D, E , K) absorbed | travel in micelles and are absorbed by simple diffusion |
| how are water soluble vitamins absorbed (B, C) | absorbed by simple diffusion |
| how are vitamins B12 absorbed | combines with intrinsic factor and is absorbed in the ileum via active transport |
| what are the four regions of the large intestine? | cecum, colon, rectum, anal canal |
| what is the appendix? | coiled tube attached to the cecum |
| what is appendicitis? | inflammation of the appendix due to blockage of the lumen by chyme, foreign body carcinoma stenosis or kinking |
| what are the regions of the colon | ascending, transverse, descending, sigmoid |
| what is the rectum | last 8 inches of the GI tract anterior to the sacrum and coccyx |
| what is the anal canal | terminal 1 inch of the rectum |
| what are the two spinsters of the anal canal? | internal anal sphincter: smooth muscle and involuntary external anal sphincter: skeletal muscle and voluntary control |
| what is the internal anal spinster? | smooth muscle and involuntary |
| what is the external anal sphincter? | skeletal muscle and voluntary control |
| what is the teniae coli? | thickened bands formed by the external longitudinal smooth muscles run along the large intestine |
| what are haustra? | pouches formed as a result of tonic contractions of the Teniae coli |
| what are the mechanical digestion in the large intestine? | smooth muscle, peristaltic waves, austral churning, gastroileal reflex, gastrocolic reflex |
| what is austral churning | relaxed haustra (pouches) become distended when they are filled the walls contract and squeeze the contents into the next haustrum |
| what is gastrioileal reflex? | when stomach is full, peristaltic wave is intensified in the ilium and gastrin hormone relaxes ileoceal sphincter so chyme is forced from ilium into cecum |
| what is gastrocolic reflex? | peristaltic wave begins at the middle of the transverse colon and moves the contents of the colon into rectum initiated by food in the stomach |
| what is absorbed in the large intestine? | water, electrolytes Na+ Cl-, vitamins K and B |
| what s chemical digestion in the large intestine? | no enzymes are secreted only mucous bacteria break down carbohydrates into carbon dioxide and methane gases, convert undigested proteins into amino acids and cause odor and turn bilirubin into simple pigments that gives fever brown color |
| what vitamins to bacteria produce in the large intestine | B and K |
| what does feces consists of? | dead epithelial cells, undigested food such as cellulose and bacteria both live and dead |
| how does defecation work? | gastrocolic reflex moves feces into rectum stretch receptors signal sacral spinal cord parasympathetic nerves contract muscles of rectum and relax internal anal sphincter external anal sphincter is voluntarily controlled |
| what happens in diarrhea | increase in frequency, volume and fluid content caused by increased intestinal motility and decreased intestinal absorption chyme passes too quickly through intestine water absorption decreases |
| what happens in constipation | difficult defection caused by decreased intestinal motility, too much water is reabsorbed the feces become dry and hard |
| what is insoluble water? | woody parts of plants, speeds passage of materials through the GI tract and reduces colon cancer |
| what is soluble fiber? | rich in beans, oats, citrus fruits, apples form a gel that slows the passage of material through the GI tract lowers blood cholesterol by preventing reabsorption of bile salts so liver has to use cholesterol to make more |
Created by:
Chobchi
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