Gastroenterology in Critical Care

Anatomy and Function of the Liver and Gallbladder

nursebob 07/25/10

The liver is the largest gland in the body. It weighs about three pounds (1.4 kg) in the average size adult. It is about 4-8 cm in Height at the midsternal line and about 6-12 cm in Height at the midclivicular line. The liver is located in the right side of the abdomen, inferior to the diaphragm and anterior to the stomach.

The liver has four lobes right, left, to date, and quadrant. A mesentery ligament separates the right and left lobes and suspends the liver from the diaphragm and anterior abdominal wall. It is encased in a fibroelastic capsule.

In order to survive the liver requires 25 percent of the cardiac output. H. The liver receive 25% of cardiac output. The major vessels of the liver are the portal vein which removes blood from the liver and the hepatic artery which supplies blood to the liver.

Liver tissue is made up of units called lobules. These are composed of plates of hepatocytes (liver cells). Communicating with each lobule are a branch of the hepatic artery, a branch of the hepatic portal vein, and a bile duct. Sinusoids are blood filled spaces within the lobules. These are lined with Kupffer cells - phagocytic cells which remove debris from the blood.

The functions of the liver are many:

1. The secreation of bile, storage of fat-soluble vitamins (A, E, D, and K)
2. The matabolization of bilirubin.
3. The storage of blood which can be released during during hemorrhage
4. The synthesizes of plasma proteins to maintain plasma osmotic pressure
5. The synthesizes of prothrombin, fibrinogen, and factors I, II, Vii, IX, and X which are necessary for blood clotting.
6. The synthesizes fats from carbohydrates and proteins to be either used for energy or stored as adipose tissue.
7. The synthesizes phospholipids and cholesterol necessary for the production of bile salts steroid hormones and plasma membranes.
8. The conversion of amino acids to carbohydrates through deamination.
9. The releases glucose during times of hypoglycemia.
10. Takes up glucose during times of hyperglycemia and stores it as glycogen or converts it to fat.
11. Alters chemicals, foreign molecules and hormones to make them less toxic
12. Stores copper and releases it as needed.
13. Stores iron as ferritin, which is released as needed for the production of red blood cells.

The liver's digestive function is to produce bile which is a greenish, watery solution containing bile salts cholesterol, bilirubin, electrolytes, water, and phospholipids. It is necessary to emulsify and promote the absorption of fats. Liver cells make from 700 to 1200 mi of bile every day. When bile is not needed for digestion, the sphincter of Oddi (located at the point at which bile enters the duodenum) is closed, and the bile backs up the cystic duct into the gallbladder for storage. Bile is concentrated and stored in the gallbladder, a small sac cupped in the inferior surface of the liver. When food containing fats enters the duodenum, hormones stimulate the gallbladder to secrete bile into the cystic duct. The cystic duct joins the hepatic duct to form the common bile duct from which bile enters into the duodenum. Bilirubin is not water soluble. The liver removes it from blood. It is excreted in Bile. This is what gives Stool Brown Color. Barbiturate, sedatives are detoxified by the liver. Tylenol is toxic to the liver.

Reference: Nursebob's notes.

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