# 134 - Gall bladder, human, h-e, 1,5 mm

# 133 - Gall bladder, monkey

Bile from the liver is stored in the small pear-shaped gall bladder. During digestion, the gastrointestinal hormone, CCK (cholecystokinin - pancreozymin) triggers its discharge from the gall bladder by causing the musculature of the gall bladder to contract. Bile is released into the small intestine where it acts as an emulsifier of fat.

The gall bladder is lined by simple columnar epithelium with a thin lamina propria that blends imperceptibly with the submucosa since there is no muscularis mucosae. Normally, there are also no goblet cells here except in the neck region. The mucosa of a relaxed gall bladder is thrown into extensive folds, but there are no true villi present . Diverticuli (sinuses) may be present.

The external muscle layer is thin, ill-defined and interlacing; the smooth muscle bundles run in several different directions. Below the muscle layers is a broad band of perimuscular connective tisssue. The organ is covered by a serosa, except where it is attached to the capsule of the liver by an adventitia. See Gartner, p. 289 and Ross, pp. 526 - 527.

The luminal epithelium is columnar but without goblet cells. THERE ARE NO VILLI HERE. The folded mucosa gives rise to pockets or diverticuli called Rokitansky-Aschoff sinuses. A characteristic feature of the gall bladder is the patches or strips of smooth muscle interspersed with connective tissue. There is no layering of the muscles as there is in the intestines for example. Compare the thickness of the wall to that of the other regions of the intestine.

In the cellular lamina propria of the gall bladder you will see lymphocytes. You may also see neutrophils or eosinophils. What organ lies adjacent to the gall bladder (see Slide 133)?

REFERENCES: Gartner, p. 308 - 309 Ross, pp. 526 - 527 DiFiore, p. 223, Fig. 14-9 Wheater, p. 278, Fig. 15.12