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Anatomy of Gall Bladder ;
Arterial and Lymphatic Supply of Gall Bladder.
Bile, as it
leaves the liver, is composed of 97% water, 1 to 2 % of bile salts,
and 1 % of pigments, cholesterol, and fatty acids.
The liver
excretes bile at a constant rate, estimated at 40 ml per hour.
Except when
active gastroduodenal digestion is in progress, the sphincter of
Oddi contracts and consequently bile leaving the liver passes
into the gall-bladder.
The healthy gall-bladder has several functions :
- Concentration
of bile : By the active absorption of water, sodium, chloride, and
bicarbonate by the mucous membrane of the gall-bladder into the
bloodstream and to a lesser extent into the lymphatics, the hepatic
bile which enter the gall-bladder becomes concentrated from 5 to 10
times, with a corresponding increase in the proportion of bile salts,
bile pigments, cholesterol, and calcium it contains.
- Reservoir for
bile : Bile is stored until the gall-bladder is full, when the
sphincter of Oddi partially relaxes and the overflow trickles into the
duodenum. Contraction of the gall bladder and synchronous relaxation
of the sphincter of Oddi is stimulated by cholecystokinin, a hormone
secreted by the duodenum in response to acid chyme, fats and egg yolk
or magnesium sulphate in its lumen.
-
Changing the
reaction of the bile : The bile excreted by the liver is alkaline
(pH 8.2), whereas that in the gall bladder becomes acid (pH 7.6 to 7)
as the bile becomes concentrated.
- Cholesterol
excretion by the gall bladder has not been proved, but pathological
evidence of the gall-bladder epithelium choked with crystalline
cholesterol is suggestive that the gall-bladder may add cholesterol to
the bile.
- Secretion of
mucin : About 20 ml. is secreted each twenty-four hours.
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