Liver

The largest organ of the body, this roughly wedge-shaped, red-brown structure lies in the upper right abdominal cavity, directly below the diaphragm. The liver is divided into 2 main lobes, each consisting of many lobules. These lobules are surrounded by branches of the hepatic artery, which supplies the liver with oxygenated blood, and the portal vein, which supplies nutrient-rich blood. Deoxygenated blood from the liver drains into the hepatic veins. A network of ducts carries bile from the liver to the gallbladder and the small intestine. The liver plays a vital role in the body because it produces and processes a wide range of chemical substances. The substances produced include important proteins for blood plasma, such as albumin. The liver also produces cholesterol and special proteins that help the blood to carry fats around the body. In addition, liver cells secrete bile, which removes waste products from the liver and aids the breakdown and absorption of fats in the small intestine (see biliary system). Another major function is the processing of nutrients for use by cells. The liver also stores excess glucose as glycogen. In addition, it controls the blood level of amino acids (the building blocks of proteins). If the level of amino acids is too high, the liver converts the excess into glucose, proteins, other amino acids, or urea (for excretion). Finally, the liver helps to clear the blood of drugs and poisons. These substances are broken down and excreted in the bile.