Page 645 - Atlas of Histology with Functional Correlations

Surrounding smooth muscle fibers (10) is a thick layer of dense connective

tissue (6) with blood vessels—artery and vein (11)—lymphatics, and nerves
(5).

Serosa (12) covers the entire unattached gallbladder surface. Where the
gallbladder is attached to the liver surface, this connective tissue layer is the
adventitia.

FIGURE 16.17 ■ Wall of the gallbladder. Stain: hematoxylin and eosin. Low

magnification.

FUNCTIONAL CORRELATIONS 16.4 ■

Gallbladder

The primary functions of the gallbladder are to collect, store, concentrate,

and expel bile when needed for emulsification of fat. Bile is continually
produced by liver hepatocytes and transported via the excretory ducts to the
gallbladder for storage. The epithelial cells in the gallbladder contain
organelles similar to those in cells that participate in transmembrane transport
of molecules. Here, sodium pumps in the basolateral membranes actively

transport sodium through the epithelium into the extracellular connective
tissue, creating a strong osmotic pressure. Most of the water and chloride
ions passively follow from the bile, producing a highly concentrated bile.

Release of bile into the duodenum is under hormonal control. In response

to dietary fats in the proximal duodenum, the hormone cholecystokinin
(CCK) is released by enteroendocrine cells in the intestinal mucosa. CCK is

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