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52 Cards in this Set
- Front
- Back
What does the liver secrete?
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Bile
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What is Bile vital for? (2 processes)
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1. Fat digestion and absorption
2. Excretion of waste (bilirubin) |
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2 stages of bile secretion:
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1. Hepatocyte secretion
2. Bile flow |
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How does the primary hepatocyte secretion of bile acids and cholesterol get changed as it flows through the ducts?
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Sodium bicarb and Water get added to increase the quantity of bile.
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What stimulates the addition of Water/Bicarb to bile?
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Secretin
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2 Places where Bile can go after secretion from the hepatic duct:
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1. Directly to duodenum
2. To store in gallbladder |
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What is the max absolute vol of the gallladder?
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30-60 ml
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How much bile can the gallbladder hold?
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12 hrs worth - 450 mL - but in CONCENTRATED FORM
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Components of Bile in the gallbladder:
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-Bile salts
-Cholesterol -Lecithin -Bilirubin |
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What is the primary bile salt?
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Cholic acid
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What happens when bile salts enter the intestine?
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Conversion to 2ndary bile salts by intestinal bacteria
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What happens to 2ndary bile salts?
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Conjugation to Glycine and Taurine
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What happens after bile salts do their job in the intestine?
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They are recirculated back to the liver for reuse.
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What stimulates emptying of the gallbladder?
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Fatty food in duodenum -> stimulates CCK -> stimulates gallbladder contractions and relaxation of sphincter of oddi
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What else can stimulate gallbladder emptying, other than CCK?
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-Vagal nerves
-ENS nerves (though these are less potent) |
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Why is it bad to not eat fat?
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Because you won't have good gallbladder emptying if there's no fat to stimulate CCK release.
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Effect on gallbladder by each:
-CCK -Secretin |
-CCK stimulates GB contraction and Sph of Oddi relaxation
-Secretin stimulates ductal secretion (bicarb/water) |
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Precursor of bile salts:
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Cholesterol
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What is cholesterol converted into?
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Cholic acid or Chenodeoxycholic acid
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What happens to primary bile acids?
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Conjugation to glycine/taurine to form bile acids
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What happens to conjugated bile acids?
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Linked to Na forming bile salts; secreted into bile.
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2 important actions of bile salts:
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1. Detergent action on fats (emulsification)
2. Absorption of fats |
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How do bile salts allow absorption of fats?
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-Emulsification increases SA for lipase action on them
-Form micelles to carry them in the bloodstream. |
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What would be the case if there were no bile salts?
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40% of lipids could not be absorbed.
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How are bile salts reabsorbed from the intestine after doing their job?
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50% by active transport
50% by diffusion -INTO THE BLOOD |
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Why is bile circulation and reuse important?
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It controls the amt of synthesis by the hepatocytes.
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What happens if bile enterohepatic circulation is blocked?
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Liver production of bile will increase dramatically.
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Why does secretin stimulate bile secretion after a meal?
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To aid in acid neutralization and for optimal function of pancreatic enzymes.
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What is the function of cholesterol secreted in bile?
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unknown
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What happens to cholesterol and the other constituents of bile in the gallbladder?
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Everything gets concentrated together
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What happens if cholesterol precipitates out?
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Gallstones
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What favors gallstone formation?
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-High fat diet
-Inflamed gallbladder epithelium |
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2 types of glands in the SMALL intestine:
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1. Brunner's glands
2. Crypts of Lieberkuhn |
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What do brunner's glands secrete? Where?
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Mucus - in duodenum between pylorus and papilla of Vater
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What type of mucus do Brunner's glands secrete?
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Alkaline
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What stimulates secretion from Brunner's glands?
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-Tactile/irritation
-Vagal stimulation -GI tract hormones - especially secretin |
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Function of alkaline mucus:
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protection from acidic degradation
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What is a strong inhibitor of Brunner's gland secretion?
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SNS stimulation - common cause of peptic ulcers in the proximal duodenum.
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Where are digestive products secreted in the small intestine?
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Crypts of Lieberkuhn
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Where are crypts of lieberkuhn located?
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In pits between intestinal villi
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What covers crypts of lieberkuhn?
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An epithelium composed of:
-Goblet cells (secrete mucus) -Enterocytes (absorptive, secrete water/electrolytes). (this also covers villi) |
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What happens to the secretions of crypts of lieberkuhn?
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They are immediately absorbed by villi in a cyclical fashion, along with digested endproducts
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What is the mechanism by which crypts of lieberkuhn secrete fluid and electrolytes?
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Electrogenic Cl- secretion - bicarb, sodium, and water follow.
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How much of small intestine secretions consist of enzymes?
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Very little
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If there are enzymes in the sm intestine where are they located?
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In brush border of mucosal enterocytes
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3 enzymes in enterocyte brush border:
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1. Peptidases
2. Enzymes for disaccharides 3. Intestinal lipase |
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What stimulates small intestine secretions?
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The presence of chyme / irritations
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What is the most important stimulus for small intestine secretion?
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Local stimuli
-tactile irritants -Increased ENS via incr motility |
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What hormones stimulate small intestine secretion (if any - this is of minor importantce)
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-CCK
-Secretin |
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What are the lumenal epithelia of large intestine like? (cell types)
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-Many crypts of lieberkun
-Many goblet -No villi |
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What goes on at the crypts of lieberkuhns in lg intestine?
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-Secretions of alkaline mucus
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What stimulates lg intestine mucus secretion?
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-Tactile stimulus
-Local reflexes to goblet cells -PNS stim (s2-s4) to distal 60% of the lg intestine |