Digestive Glands and Associated Organs
ampulla (of Vater)
is a pear-shaped, saclike organ that stores, concentrates, and releases bile. It connects directly to the cystic duct, which is an extension
of the gallbladder. Bile from the right and left hepatic ducts drains into the common hepatic duct, which connects to the cystic duct and enters the gall-
bladder. The gallbladder releases bile in response to
. The gallbladder has a thin wall, which is composed of three layers. (1) The
is the innermost layer, lined by simple columnar epithelium, with many microvilli on the apical surfaces and a lamina propria (loose connective tissue)
beneath the epithelium. The mucosa has many branching folds. (2) The
consists of interlacing longitudinal and obliquely oriented bundles
of smooth muscle F bers. The contraction of these muscle F bers helps empty bile through the cystic duct into the bile duct. The
spiral valve of Heister
(smooth muscle at neck of the gallbladder) controls the opening or closing of the gallbladder. The bile duct joins the pancreatic duct at the hepatopancre-
atic ampulla, and bile enters the duodenum through the major duodenal papilla. (3) The
is a connective tissue that covers most of the gallbladder.
It contains mesothelium and is continuous with the covering of the liver. The
attaches the gallbladder to the liver and lacks a mesothelium.
Epithelial cells lining the gallbladder.
There are many short
on the apical surfaces of the columnar cells that line the
. Numerous microvilli indicate the function of
these cells, which is to absorb water from bile in the lumen and transport it into the interstitial tissue. Concentrating bile is one of the main functions
of the gallbladder. The
interdigitating lateral membranes
at the lateral borders of the columnar cells are typical of water-transporting cells. Many
are in the cytoplasm of these cells, and are more numerous in the superior region. The
shows the basal region of the epithelium.
Oval-shaped nuclei are located close to the basal lamina.