mastication carried out by teeth to break food into smaller pieces, mix food with saliva, stimulate taste buds tongue forms floor of oral cavity taste buds responsible for taste, reflex (move food down esophagus), increas in salivary, gastric, pancreastic and bile secretionfunction of mouthheld together by periodontal ligament enamel (outside) dentin is inside, root canal has nervetooth structureproduce saliva, which performs the initial steps in digestion, lubricates food to make it easier to swallow, and facilitates oral hygiene by flushing away food residues continuous level of salivary secretion, increase in response to food saliva produced from parotid, submandibular, sublingual and associated ductsfunction of salivary (exocrine) glandscontains ions, mucus, amylase, lysozyme, lingual lipase mucus: provides lubrication amylase: polysaccharides --> maltose lysozyme: destroy bacterial cell walls lingual lipase: digest triglycerides to fatty acids and monoglyceridessalivaafter chewing, becomes bolus of food to initiate swallowing reflex swalloing center of brain closes respiratory passage, food goes to stomachfunction of pharynx and esophaguscalled deglutition three phases: buccal, pharyngeal, esophageal last two phases are involuntary (triggered by pharyngeal stretch)swallowingGI tract is organized by twosets of muscles: outer layer is longitudinal muscle (propels food forward) inner layer: circular muscle: prevents foor from moving backperistalsisgastroesophageal sphincter remains contracted except during swallowing to provide barrier between stomach and esophagus stores ingested food until small intestine is ready to process it further for final absorption secretes HCl and enzymes taht begin protein digestion mixing waves and gastric secretions produce a thick, liquid mixture called chymefunction of stomachgastric contents flows back into esophagus normally, sphincter is closed, when its open while mixing, acid goes back this is called gastroesophageal reflux causes: overeating, chronic (defect in sphincter)cause of heartburnlined with epithelial cells, gastric gland has parietal cells, G cells, and chief cells below the gastric pit: submucosa oblique muscle circular muscle longitudinal musclegastric pitacid is necessary for conversion of inactive pepsinogen to pepsin to begin digestion of protein. Makes peptides active site of pepsin is blocked, HCl cleaves pepsinogen to activate it also kills most bacteria HCl is secreted from parietal cells in lining of stomach and H/K ATPase, Cl- secreted along with it as well stomach withstands acidity because of its mucus, but damage or erosion of stomach results in peptic ulcer. H. Pylori is cause of peptive ulcerHCl secretion in stomachpepsinogen is released from chief cells located in stomach by exocytosis HCl cleaves off a small part of the molecule and converts it to pepsin Pepsin breaks certain peptide bonds within proteins to make peptidessecretion of pepsinogenHCl, pepsinogen, mucus (gastric juice) stimulated by nervous system partially digested proteins also stimualte release of gastrin, hormone which also stimulate HCl secretion No ingested food is absorbed into blood from stomach, except alcoholregulation of gastric secretion3 sections: duodenum, jejunum, ileum most digestion and absorption takes place here no further digestion/absorption after SI chyme in SI ontain partially digested carbs, proteins and lipids. To complete digestion, need pancreatic juice, bile, intestinal juice circular folds: villi designed to increase surface area for absorptionsmall intestinelots of blood supply and lymph nodes to each villi covered in epithelial cell nutrients pass through epithelial cell mechanism to increase surface area: circular folds, villi, microvillivilli in small intestinemade by acinar cells (exocrine glands) of pancreas contains water, salts, sodium bicarbonate and enzymes alkaline, stops action of pepsin from stomach (bicarb is responsible for this) stimulated by nervous system, secretin and cholecystokinin (CCK) produced in intestinal mucosapancreatic juicepancreatic amylase: carbohydrate digesting trypsin, chymotrypsin, carboxypeptidase: protein digesting pancreatic lipase: triglyceride digesting ribonuclease and deoxyribonuclease: nucleic acid digestingenzymes in pancreatic juiceproduced by liver and stored in gallbladder CCK causes release of bile from gallbladder bile contains bile salts, derivative of cholesterol to aid in fat digestion through detergent action (ampipathic) fat is absorbed via formation of water soluble micelles micelle structure: triglyceride in center, nonpolar steroid ring of bile salt binds to TGL, carboxylic acid tail of bile sticks out, on water sidebileBile contains cholesterol and fatty acids 1. chyme coming out of stomach has big droplets of fat. Bile salts/phospholipids break it down into smaller droplets that are emulsion droplets . 2. Emulsion droplets become micelles via bile salts and panreatic lipase. 3. TGL splits into fatty acis and monoglycerides 4. FA and monoglycerides readily class epithelial cell of small intestine (nonpolar) 5. in epithelial cell, TGL resynthesized, associated with ER, packed in vesicles. Exocytosis to form chylomicron 6. Chylomicron enters lymph systemdigestion of fatsslightly alkaline, maintain fluidity of chyme 3 enzymes to convert disaccharides to monosaccharidesintestinal juicemaltose --> two molecules of glucosemaltasesucrose --> glucose _ fructosesucraselactose --> glucose + galactoselactasevia active transportHow does glucose enter epithelial cell?to the blood vessel in the subclavian veinWhere does the lymph system drain to after chylomicron goes to it?Secondary trasnport of sodium gradient, diffusion of cotransport into the bloodstreamHow does protein cross the epithelial cell?small intestine, bile salts emulsify globules of TGL facilitating breakdown by pancreatic lipase to FA and monoglycerideWhere does lipid digestion occur in adults?

Digestion

Students also viewed

Other sets by this creator

Verified questions

Other Quizlet sets