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52 Cards in this Set

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