Info

Liver Bile

Gallbladder Bile

Water

97.5 g/dl

92 g/dl

Bile salts

1.1 g/dl

6 g/dl

Bilirubin

0.04 g/dl

0.3 g/dl

Cholesterol

0.1 g/dl

0.3 to 0.9 g/dl

Fatty acids

0.12 g/dl

0.3 to 1.2 g/dl

Lecithin

0.04 g/dl

0.3 g/dl

Na+

145.04 mEq/L

130 mEq/L

K+

5 mEq/L

12 mEq/L

Ca++

5 mEq/L

23 mEq/L

Cl-

100 mEq/L

25 mEq/L

hco3-

28 mEq/L

10 mEq/L

This is the same cholecystokinin discussed earlier that causes increased secretion of digestive enzymes by the acinar cells of the pancreas. The stimulus for cholecys-tokinin entry into the blood from the duodenal mucosa is mainly the presence of fatty foods in the duodenum.

In addition to cholecystokinin, the gallbladder is stimulated less strongly by acetylcholine-secreting nerve fibers from both the vagi and the intestinal enteric nervous system. They are the same nerves that promote motility and secretion in other parts of the upper gastrointestinal tract.

In summary, the gallbladder empties its store of concentrated bile into the duodenum mainly in response to the cholecystokinin stimulus that itself is initiated mainly by fatty foods. When fat is not in the food, the gallbladder empties poorly, but when significant quantities of fat are present, the gallbladder normally empties completely in about 1 hour. Figure 64-11 summarizes the secretion of bile, its storage in the gallbladder, and its ultimate release from the bladder to the duodenum.

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