- Education and Science
Where is your Gallbladder?
The gallbladder is a small pouch attached to the side of the bile duct, the tube that carries bile from the liver to the small intestine. A gallbladder is found in about two thirds of all vertebrate animals. Its function is to concentrate and store bile, which is produced by the liver, until it is needed for digestion.
Storage and Concentration of Bile
The human gallbladder usually ranges in length from about 2.75 to nearly 4 inches and can hold up to 2 ounces of bile at anyone time. The outer wall is composed of muscle, and when it contracts the gallbladder empties. The inner wall is absorptive. When there is no digestion occurring in the small intestine the muscle surrounding the intestinal end of the bile duct is tightly closed, and the bile, as it is produced by the liver, flows into the gallbladder and distends it.
The liver normally produces from 13 to 32 ounces of bile each day. As it is produced, the bile contains 97% water, 2.5% bile salts, and 0.5% other solids. The gallbladder removes much of the water from the bile and may concentrate it as much as twelvefold. After it is concentrated by the gallbladder the bile may contain 50% bile salts.
Release of Bile
When ingested fat reaches the small intestine a hormone called cholecystokinin is secreted by the intestinal wall and released into the bloodstream. This hormone causes the muscle at the intestinal end of the bile duct to relax and also causes contraction of the muscle forming the outer wall of the gallbladder.
This process empties all of the bile from the gallbladder into the small intestine. The bile salts in bile are essential for the absorption of fat from the intestine and the gallbladder continues to contract and empty as long as unabsorbed fat remains in the intestine.
About 90% of the bile salts emptied into the intestine are later reabsorbed into the blood from the terminal portions of the small intestine. This process may be so rapid that the bile salts released by the gallbladder at the beginning of a meal may be reabsorbed and used to form more bile for use during the same meal. About three hours after a meal, all the body's bile salts are back in the gallbladder, where they are stored until they are needed again.
Diseases and Disorders of the Gallbladder
The gallbladder, like other organs, is subject to a variety of diseases and disorders. Among these are various infections and cancer. One of the most common disorders of the gallbladder is the formation of gallstones (cholelithiasis). Gallstones occur more frequently in older people than younger people, more in women than in men, more in the obese than in the thin, and more in American Indians and Caucasians than in African Americans.
Sometimes gallstones obstruct the drainage of bile to the gallbladder or injure the gallbladder wall, producing severe pain and sometimes causing the gallbladder to rupture. If the gallstones block the flow of bile through the bile duct, the dammed up bile may damage the liver.
Whenever gallstones cause severe pain or damage they are removed surgically. The removal of the gallbladder causes no known ill effects.
Occasionally, a person is born without a gallbladder.