Digestive System: The Gallbladder

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Gallbladder

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STORAGE, NOT PRODUCTION
-stores & modifies bile
-bile secreted by hepatocytes into bile canaliculi, from which it flows in the right & left hepatic ducts, common hepatic duct & then into gallbladder via cystic duct
-bile stored until stim of contraction expels bile back thru cystic duct into common bile duct & via sphincter of oddi into duodenum

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Regulation of Bile Secretion

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1. Secretin: stim. ion & water secretion by bile duct
-makes bicarbonate in pancreas
-stops stomach motility & gastric phase
2. CCK: contraction of gallbaldder, relaxation of sphincter of oddi
3. Ach: contraction of gallbaldder, ParaNS response

during interdigestive periods gallbaldder fill bc it is relaxed (SNS-->b2 receptors) & the sphincter of oddi is closed

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Do We Need a Gallbladder?

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-periodic discharge of bile from gallbladder aids digestion but not essential
-cholecystectomized pat. maintain good health & nutrition w/ constant slow discharge of bile into duodenum
-eventually common bile duct becomes somewhat dilated & more bile tends to enter duodenum after meals than at other times

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Lapaoscopic Cholecystecomy

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-perform as outpatient procedure & done w/ general anesthesia, laparoscopic cholecystectomy requires just 4 small incisions for a cannula (narrow tube-like instrument) near belly-button laparoscope (telescope) & tiny camera to separate gallbladder from what it is attached to & remove it
-incision closed w/ stitches or surgical tape
-generally has less pain than open surgery
-faster recovery (usually 5-7 inch incision in ab)

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Gallstones

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-cholelithiasis: presence of gallstones
-incidence increases w/ age (20% women & 5% men bw age 50-65)
-stones 2 types: calcium bilirubinate stones & cholesterol stones
-in US & europe 90% of stones are cholesterol
-asymptomatic, cause symptoms when abstruct bile flow (larger stones)
-pain of biliary colic: increase in steadily in intesnsity until it reaches climax in 30-60min
-upper right quad = location of pain, can refer pain to back, above waist, shoulder, & right scapula
-few persons experience pain on left side
-pain persists ~2-8hrs, follewed by soreness in upper right quad
-some pt. w/ stones will develop pain upon eat fatty foods as consequence of CCK-stim gall bladder contractiong agains occluded duct

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3 factors involved in form of cholesterol stones:

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1. bile salts: as stones form bile that is sequestered in gall bladder rather than bile that is flowing in the bile ducts
2. supersaturation of bile w/ cholesterol: chol very insoluble in bile, & maintained in sol'n in micelles only at certain concentrations of bile salts & lecithin
3. inflammation of gallbladder (cholecystitis)

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Cholelithiasis Risk Factors

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beside age, are many other risk factors involved w/ cholelithiasis:
-gender: higher prev. of gallstones has been observed in women of all age groups
-pregnancy: sex hormones cause bile to become supersaturated w/ chol.
-oral contraceptive use
-family history/genetics (esp in native americans)
-obesity: well est. risk factor for development of chol gallstones
-rapid-weight loss: mxn by which this occurs in imcompletely understood
-DM: not well understood; 2 possible contrib factors are hyperlipidemia & autonomic neuropathy lead to biliary stasis due to gallbaldder hypomotility

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Black Pigment Stones

Brown Pigment Stones

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Increase in levels of unconjugated bilirubin: saturates out & precipitate
-congenital abnorm, hemolysis (sickle cell anemia), liver disease, fasting

black infected due to bacterial infection
-due to surgical or endoscopic procedure or stasis

Gray stool = decrease bile & lots of fat in diet