Gallbladder

Definition

The gallbladder, an organ of the gastrointestinal system involved in the storage and concentration of bile, is shaped like a deflated balloon or pear, and lies on the surface of the right lobe of the liver .

Description

The gallbladder is pear-shaped and generally about 3–4 in (7.6–10.2 cm) in length. It consists of three parts. The fundus is the closed, bottom portion of the gallbladder that borders the liver. The body is the largest section of the gallbladder. In adults, the gallbladder can hold between 0.67 and 1.69 fl oz (20–50 ml) of bile. The neck of the gallbladder is much narrower than the body and empties into the cystic duct.

Function

The gallbladder acts like a storage tank for bile (a bitter, greenish yellow liquid composed in part of cholesterol, bile salts, and bile pigment). Bile is made in the liver and travels through the hepatic duct to be stored and concentrated in the gallbladder until the body needs it to help break down ingested fats . When the gallbladder receives a signal from cholecystokinin (a hormone) in the small intestine , it contracts and releases bile into the common bile duct, where it travels to the small intestine to help digest fats.

Role in human health

While the body can function normally without a gallbladder, this accessory organ of digestion is important to the proper digestion of fats.

Common diseases and disorders

One of the most common disorders of the gallbladder occurs when cholesterol mixes with bile and calcium , forming gallstones. Gallstones occur most frequently in middle-aged women, but they can also occur in people suffering from obesity , diabetes, hyperthyroidism, or any other disease that results in increased levels of cholesterol. When the stones stay in the body of the gallbladder they generally cause no pain or other symptoms. However, if a stone travels out into the neck of the gallbladder or into one of the bile ducts, nausea, vomiting, and severe pain follow. The patient may also become jaundiced. Gallstones usually have to be removed surgically. In severe cases, the entire gallbladder must be removed.

Other diseases can also cause obstruction of the neck of the gallbladder, causing symptoms like those of gallstones.

KEY TERMS

Adenocarcinoma —Any one of a large group of cancerous, epithelial cell tumors of the glands.

Biliary tree —Also referred to as biliary tract, it includes all of the parts associated with the passage of bile, beginning at the liver and ending at the opening of the bile duct into the small intestine.

Cholecystitis —Acute or chronic inflammation of the gallbladder.

Cholecystokinin —The hormone manufactured in the lining of the small intestine that signals the gallbladder to release bile.

Cystic duct —The duct that allows passage of bile from the gallbladder to the common bile duct.

Crohn's disease , pancreatitis (inflammation of the pancreas ), echinococcosis (infestation of the digestive system by tapeworms), and ascariasis (infestation of the digestive system by parasitic nematode worms) can all produce swellings that obstruct the gallbladder's neck.

Cholecystitis, or inflammation of the gallbladder, causes sharp, severe pain in the upper right portion of the abdomen. Cholecystitis causes fever , nausea, and vomiting; and, if left untreated, can be life-threatening.

Cancer that invades any portion of the biliary tree can interrupt or prevent the normal flow of bile and result in multiple complications. Two of the most common malignancies that occur in the biliary tract involve adenocarcinoma of the gallbladder itself or of the bile ducts that carry bile from the gallbladder.

Resources

BOOKS

Anatomy and Physiology. Springhouse, PA: Springhouse Corporation, 1998, pp.126-7.

Bray, John J., et al. Human Physiology. 4th ed. Malden, MA: Blackwell Science, Inc., 1999, p. 495.

Higgins, Christopher. Understanding Laboratory Investigations. Malden, MA: Blackwell Science, Inc., 2000, p.162.

The Merck Manual, edited by Mark H. Beers, and Robert Berkow. 17th ed. Whitehouse Station, NJ: Merck Research Laboratories, 1999, pp. 400-1.

Wilson, Denise D. Nurse's Guide to Understanding Laboratory and Diagnostic Tests. Philadelphia, PA: Lippincott Williams & Wilkins, 1999, p. 306.

PERIODICALS

Ashmallala, Hani, et al. "Recurrent Cholangiocarcinoma: Negative Autopsy Results After Aggressive Management." South Medical Journal vol. 93, no. 6(2000): 603-605.

Susan Joanne Cadwallader