GALLBLADDER

Origin: evagination of the wall of the foregut.

Location: postinferior surface of the liver.

Function: concentrates and stores bile.

BILE

Composition and function:

• Water - solute in which other components are cared.
• Cholesterol and phospholipids - metabolic substrates, precursors of membrane components and steroids.
• Bile salts (acids) - emulsifying agents that aid in the digestion and absorption of lipids from the gut.
• Bile pigments - detoxify bilirubin and carry it to the gut.
• Electrolytes - maintain bile as an isotonic fluid.

Anatomic features

• The cystic duct connects the common hepatic duct and carries bile to and out of the gallbladder. Distal to the junction the fused duct is called the common bile duct and extends to the ampulla of Vater on the duodenum. The thickening of the muscularis externa at the ampulla constitutes the sphincter of Oddi.
• The gallbladder is distensible pear-shaped sac.

MUCOSA

Function: fluid and salt absorption.

Composition:

• Simple columnar epithelium
• Lamina propria - loose connective tissue rich in lymphocytes and plasma cells with numerous fenestrated capillaries and small venules
• Mucin secreting glands.

MUSCULARIS EXTERNA

Function: contraction and discharge of concentrated bile into duodenum.

Composition: randomly oriented bundles of smooth muscle cells with numerous collagen and elastic fibers.

ADVENTITIA OR SEROSA

Composition:

• attached surface to the liver - thick layer of dense connective tissue with large blood vessels, extensive lymphatic network, and autonomic nerves, elastic fibers and adipose tissue.

• unattached surface - thin layer of loose connective tissue covered by mesothelium.