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24 Cards in this Set
- Front
- Back
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Gastrointestinal Overview
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-designed to absorb nutrients, H2O, ions
-from outside to inside -biggest system that secretes hormones -epithelial layer/cells-how stuff moves from outside to interior of body |
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Functions of GI system
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-capture and subjugation (control)
-injestion -secretion -muscle contractions (involuntary except at start and end) -digestion-actual breakdown in food -absorption-stuff from outside-->move thru epithelial-->into interior |
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Anatomy
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-essent. a tube
-interior: lumen -foodstuff enters lumen -each region has functional differences *mouth/pharynx (voluntary) *esophagus-sternum to adam's apple , move food from mouth to stomach *stomach *small intestine-absorb nutrients in H2O (ions) *large intestine-form feces/storage *rectum (store feces) and anus |
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GI Tract Layers
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(from inside to outside)
1. serosa (cells surround organ, attach to walls of abdomen) 2. Smooth Muscle Layer (contractions) 3. submucosa (gives form to organs, stretchy) 4. mucosa (epithelial cell layer, internal of mucosa is the lumen) |
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Accessory Organs
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-salivary glands
-pancreas -liver |
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Specific Traits of the Tract
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Mouth begins digestion
1. mechanical -physically breaking apart food through chewing or mastication 2. chemical -breaking apart food using enzymes and chemicals in saliva 3. The Salivary Glands -primary glands (parotid, sublingual, submandibular) -lubricate food -protects teeth -antibacterial/antifungal *secrete 2 types of saliva a)baseline (during absence of food) *come out of sublingual and submandibular glands) b)stimulated state (in presence of food) *good for lubricating food, has digestive enzymes |
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Swallowing Reflex
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-moves bolus from the mouth through esophagus and to the stomach
-two phases: 1.voluntary 2. involuntary (from mouth through esophagus) |
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Swallowing
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-initiated voluntarily, remaining activity involuntary
-regulated by swallowing center in the brain (medulla) induce contractions to move bolus -respiration stops temporarily, resp. passages blocked -upper esophageal sphincter opens *PERISTALSIS-contractions that push bolus through mouth and esophagus -lower esophageal sphincter opens *heart burn-sphincters relax inappropriately acid goes back into esophagus |
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The Stomach
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-after esophagus and LES, food (now called ingesta) enters stomach
functions: *storage of ingesta *digestion of ingesta -chemical and mechanical *regulated emptying |
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Stomach Secretions break down ingesta
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-performs digestive function using proteases (enzymes) and acid (to break down protein)
-produces mucus to prevent secretions from damaging wall -excessive damage to gastric can result in ulcers risk: *asprin *preserved food: nitrates *high salt diet *h. pylori bacteria-get in our environ |
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Stomach Contractions: Digestion and Emptying
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-strong contractions mix bolus w/ stomach acid and enzymes
*peristalsis -as bolus breaks apart, contractions squeeze food towards small intestine *food now called chyme *mainly protein that was broken down *very acidic |
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Small Intestine
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~15 ft long
-primary site for absorption of molecules from chyme (nutrients, H2O, ions) -Three Primary Regions 1.Duodenum ~25 ft 2. Jejunum ~200cm 3. Ileum ~200cm |
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Digestion Completed in Small Intestine
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-starches-->glucose
-proteins-->AA -fats-------->free fatty acids (lot of energy) -requires digestive enzymes produced by pancreas *enzymes are exocrine secretions b/c they are squirted into duodenum in response to food stimulus *pancreas also secretes and alkaline solution (neutralizes acidic chyme form stomach) |
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Bile Secretions
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-fat digestion requires the pancreatic enzymes and bile secretions
*produced by LIVER *stored in GALL BLADDER *secreted into Duodenum @ same time that pancreatic enzymes are secreted *bile secretions emulsify fats *emulsification-coats fats w. a molecule that allows fat to suspend itself in H2O *more SA-->more room for enzymes to ingest fat droplets |
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Bile Salts
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-liver cells produce subs. called bile salts which are responsible for emulsifying fats
*synthesized from recycled ones or brand new from cholesterol -stored in GALL BLADDER -gall stones block bile duct, compromising fat digestion |
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Carbs Digestion and Absorption
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-diets consist of polysaccharides (starches) and disaccharides (lactose, sucrose)
-pancreatic enzymes break down the starches -enzymes on wall of small intestine break down the disac.--yields sugars line glucose which are readily absorbed |
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Protein Digestion and Absorption (25-30% diet)
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-dietary proteins are 1st broken down in stomach (by acid and enzymes)
-then they are broken down by pancreatic PROTEASES in small intestine -finally, enzymes embedded in small intestine wall complete digestion *yield AA and very small peptides. which can be absorbed |
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Fat Digestion and Absorption
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-recall that fat digestion required
1. Pancreatic Enzymes (lipases) 2. Bile Secretions *emusify liquids *increase surface area -as digestion of fats occurs, the products end up in these particules called MICELLES |
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Absorption of Fat Digestion Products
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-fat digestion products not water soluble
*MICELLES act as stable, soluable particle *fat digestion products move from micelle and into small intestinal cell -inside cell. products are resynthesized into fat -intestine absorbs small cells, dump into blood stream -chylomicrons-contributes levels of LDL |
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Large Intestine Anatomy
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major parts:
-cecum -ascending colon -transverse colon -descending colon -has pockets called haustra |
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Rectum and Anus
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-internal anal sphincter
*allows material in -external anal sphincter *contracts to prevent bowel movement makes it voluntary *peristaltic contractions move feces down to rectum |
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Role of Large Intestine
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-by time chyme enters, nearly all nutrients have been absorbed
-large intestine absorbs remaining H2O and ions that are in chyme -specialized contractions maximize H2O absorption -feces storage -defecation |
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Microflora of Large Intestine
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-~100 trillion bacteria live in l. intestine
-commensal bacteria roles: *produce vitamins *produce molecules that can be used for energy by l. intestine epithelial cells -can they cause problems? *yes; immune system keeps poplation in check to prevent inflammation *presence of commensural bacteria prevent pathogenic bacteria from growing too much *gas, diarrhea, inflammation arise from having high prop. of pathogenic bacteria (ex. lactose intolerance) |
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Weight Loss Surgery (Bariatric Surgery)
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-surgeries allow tremendous wt. loss/mainpulate how GI tract works
-reduce symptoms of type II diabetes, hypertension, high cholesterol -Types 1. restrictive (decrease size of stomach) 2. restrictive + Malabsorptive (mall small intestine smaller than normal) |
