For professionals:

• The liver is the largest organ in the body -- 1,200 ~ 1,500 gm.
  • It comprises about 1/50 of the total adult body weight, and it is relatively larger in infancy, comprising about 1/18 of the birth weight.
  • It is a complex organ that performs many vital functions, from regulating the levels of chemicals in the body to producing important substances including blood coagulation factors.
• The liver has two lobes, the right and the left. The right lobe is about six times the size of the left.

The liver consists of four systems:

1. Hepatocyte ( liver cell) system

2. Biliary tract system

3. Blood circulatory system

   • Dual blood circulatory system:
     The blood in the liver is supplied by two sets of blood circulatory systems:
     • A) Systemic circulation
     • B) Portal circulation

   • Blood flow of the liver: 1,300 cc of blood flow into the liver every minute, it is about 1/4 of the cardiac output.

   • 3/4 of the blood in the liver is supplied by the portal system, and the remaining 1/4 is supplied by hepatic artery from systemic circulation.

   • The liver receives blood from both the intestine and the heart. The blood then flows through a latticework of tiny channels inside the liver. Blood from the intestine and heart then mix together and flow back to the heart through the hepatic vein.

4. Reticulo-endothelial system

   • Kupffer cells: highly mobile macrophages, attached to the endothelium, phagocytic
   • Lipocytes (Ito cells): fat-storing cells in the sinusoids
   • Pit cells: highly mobile, natural killer lymphocytes attached to the endothelium
   • Endothelial cells:

1. The metabolism of carbohydrate, protein (including synthesis of protein components and coagulation factors), lipids, drugs, and excretion of dyes.
   • By-products in the bile enter the intestine, then leave the body in the feces. By-products in the blood are filtered out by the kidneys, then leave the body in the urine.

   • The liver manufactures about half of the body's cholesterol; the rest comes from food. About 80 percent of the cholesterol made by the liver is used to make bile. Cholesterol is a vital part of every cell membrane and is needed to make certain hormones, including estrogen, testosterone, and the adrenal hormones.

   • The liver also converts substances in digested food into proteins, fats, and carbohydrates. Sugars are stored in the liver as glycogen and then broken down and released into the bloodstream as glucose when needed.

2. The metabolism and excretion of bilirubin and bile acids.

3. Abnormalities of liver function can be divided broadly into two groups:
   • those caused by a malfunction of the liver cells (such as cirrhosis or hepatitis)
   • those caused by an obstruction of the biliary tract (such as bile duct stones or cancer of bile duct and hetocytes).