GI - Pathophysiology

olanjones's version from 2016-04-10 01:48

GI Tract & Mouth

Question Answer
Functions of mucosa1.Secrete mucus, dig enz, and hormones
2. Absorb end products into blood
Components of muscularisConnective tissue with BV, lymph, nerves
ANS innervation of gut1. Submucosal plexus
2. Myenteric plexus
Submucosal plexus functionStimulation of secretions from glands
Myenteric plexus functionMuscles, nerves
Carbohydrate digestion begins in the _____with action of _____ Mouth, salivary amylase
Components of saliva:Mucus, sodium, bicarb, Cl-, K+, salivary amylase, IgA
Nervous control of saliva production:PSNS


Question Answer
LES/GESconnects esophagus -> cardiac region of stomach, passes through *hiatus* of diaphragm
Cardiac region/orificesuperior area/opening of stomach near heart
Fundusupper (fun!) part
Antrum superior, wider area of pyloric region in inferior are of stomach
Rugaefolds of stomach, *maximize absorbtion
Pylorus/pyloric region inferior, funnel shaped region of stomach, proximal to duodenem
Pyloric sphincterpyloric region stomach ->duodenem

Small and Large Intestine

Question Answer
Areas of SIDuodenem, Jejunum, Ileum (Dont Jiggle the Ice)
Functions of duodenemfluid and nutritional absorption
Functions of jejunummineral absorption
Fucntions of Ileumabsorption Vits A,D,E,K, K significant for clotting.
Ileocecal valve/junction*narrowest part of lower digestive system, common inital site of Crohn's development
Muscle layers Intestinesouter = muscularis, inner = circular
Nervous controlmyenteric and submucosal plexus
Villi function small intestinemaximize absorption, brush border cells have microvilli
Large intestine functional regionscecum, appendix, ascending/transverse/descending/sigmoid colon, rectum, anus

Movements and motility

Question Answer
Reflexes stimulating defecationdefecation reflex - internal anal sphincter relaxes, valsalva maneuver - moderately forceful attempted exhalation against a closed airway, increases abdominal pressure
Factors affecting gastric motilityswallowing, gastrin secretion, Cholecystokinin (CCK), Secretin, Gastric emptying
Gastric emptying/regulationregulated by hormones + enteric plexus. If duodenem has chyme w/ pH <3.5, gastric emptying will slow b/c intestine cant handle acidity
Swallowing phasesoral-voluntary, pharyngeal-involuntary, esophageal-involuntary, intitiates peristalsis
Gastric motilityperistalsis
Small intestinal motilitysegmentation, peristalsis
Colonic motilityhaustrations, propulsive mass movement

GI Secretion

Question Answer
Control of secretionsneural, humoral (blood/hormonal), local
Components of gastric juicemucus, acid, enzymes, hormones, intrinsic factor, gastroferrin
Mucus in small and large intestine secreted bygoblet cells
Mucus in stomach secreted bymucus neck cells of gastric + pyloric glands
Mucus functionlubricate and protect mucosa
Gastric pits, form openings for what two types of glandspyloric and oxyntic/gastric glands
Pyloric glands secrete:gastrin and mucus; antrum; function to protect mucosa
Gastric/oxyntic glands cells- mucus neck cells
- peptic/chief cells
- parietal/oxyntic cells
- G cells
-Enterochromaffin-like (ECL) cells
-D cells
Gastric acid secreted byparietal/oxyntic cells
Pepsinogen secreted bypeptic/cheif cells
Pepsinogen function- proenzyme, activated to pepsin by HCl in gastric juice,
- protein digestive enzyme of stomach
Intrinsic factor and HCl secreted byparietal/oxyntic cells
Intrinsic factor functionbind Vitamin B12, facilitate absorptiuon in distal ileum

more GI Secretion!

Question Answer
Gastroferriniron-binding protein, helps absorption, keeps in Fe2+ oxidation state
Gastrin production siteG cells of antrum, parietal cells
Stimulus gastrin secretionpartially digested proteins in chyme, ACh
Target gastrinparietal cells
Function gastrin- stimulate gastric acid sectretion - growth producing, - provoke histamine response
CCK production site I cells intestinal mucosa
CCK stimulus for secretionfatty chyme, partially digested proteins
CCK targetpancreas
CCK function-*stimulate pancreatic enzyme secretion* -potentiates action of secretin - regulate gallbladder contraction and gastric emptying - inhibit food intake and appetide regulation
Secretin production siteS cells duodenem + jejunum
Secretin targetS cells duodenem, jejunum
Secretin function-*inhibit gastric acid secretion*
-stimulate bicarb output pancreas, liver
Enterochromaffin-like (ECL) cells respond toAcH, gastric stimulation
Enterochromaffin-like (ECL) produceHistamine
D cells (pancreas and gastric glands) producesomatostatin
Function somatostatindecrease secretion in stomach and pancreas, decrease GI blood flow, intestinal absorption
Histamine function in digestion-bind H2 receptor basolateral membrane of parietal cells
-increase gastric acid secretion of parietal cells by increasing activity of H+/K+ATPase pump
-site of drug action, H+ controllers / H2-agonists
Prostaglanding E2 -protective of gastric mucosa
NSAIDS, aspirin effects on gastric mucosasythesis PGE2 inhibited, mucosa protection decreased, risk of damage
ETOH, refluxed bile salts from intestine, effects on gastric mucosacan disrupt integrity of mucosal tissue, result in damage
Smoking effects on gastric mucosavasoconstriction, decrese mucosal secretions
Substances required to bind basolateral receptors on parietal cells to stimulate gastric acid secretionHistamine, gastrin, ACh
Verapamil / Ca++ channel blockers effects on digestive motilitydecrease contration of smooth muscle, relaxation of LES, exacerbate or cause GERD

Immunity and GI

Question Answer
Immune function mucosal secretionsproduce antibodies
Paneth cell functionproduce defensins + other antibiotic peptides
Peyer patchescollections of lympcytes, plasma cells, macrophages in small int
Function Peyer patches-component of gut-associated lymph tissue (GALT)
-*produce immunoglobulins*
Function of bile salts-break apart large fat globules
-form micelles to transport monoglycerides and fatty acfids to intstinal mucosa
-here, absorbed, converted to chylomicrons for xport in lymphatic channels

Chemical digestion

Question Answer
carb digestion in mouth-salivary amylase
carb digestion in duodenem-pancreatic amylase
Carb digestion performed by brush border enzymes of enterocytes of small intestine-disaccharides-->monosaccharides
-monosaccarides absorbed into blood
Protein digestion in stomachpepsin; protein-->polypeptides
Protein digestion in duodenempancreatic enzymes/proteases
Protein digestion by brush border enzymespolypeptides-->1-3 aa peptides-->absorbed into blood
Fat digestion role of bileemulsfy fats, form micelles
Fat digestion pancreatic lipasetriglycerides-->glycerol+fatty acids
Fat digestion role of bile-package fats into chylomicrons-->lymph(lacteals)
-release fatty acids into portal blood
Digestion of which substance begins in the mouth?
All of the above
Carbohydrate digestion begins in the mouth with salivary amylase; protein digestion begins in the stomach with pepsinogen; fat digestion begins in the small intestine with bile and pancreatic lipase.
How would fat digestion be affected if bile levels decreased?
It would increase.
It would decrease.
It would have no effect; fat digestion is mainly affected by amylase.
It would have no effect; fat digestion is mainly affected by lipase
It would decrease.
Rationale: Bile emulsifies fat so that it can be more easily digested. Decreased amounts of bile would lead to decreased fat emulsification and decreased ability to breakdown/digest fats.


GI Flora

Question Answer
Stomach florarelatively sterile, low pH
Duodenem floralow numbers, bile acids/motility/antibody production
Jejunum floralow # of aerobes
Large intestine/distal to ileocecal valve flora-majority of flora
-anaerobic fecal bacteria (95%)