The liver is the largest gland and largest internal organ in the human body (the skin is the largest organ overall).
Weighing 3-3.5 lbs (1.4-1.6 kg), the liver is a dark red, wedge-shaped gland approximately eight and a half inches long (roughly the size of a football). It is located in the right side of the abdominal area just below the diaphragm and above the stomach.
Approximately 1.5 qts (1.5 L) of blood flow through the liver each minute. The liver holds about 13% of the body's blood supply. It is furnished with blood from two large vessels, the portal vein and the hepatic artery (hepatic means liver). Blood that has circulated through the stomach, spleen, and intestine enters the liver through the portal vein as part of the portal circulation system. The liver extracts nutrients and toxins from this blood, which is then returned through the hepatic vein to the right side of the heart. The hepatic artery supplies oxygenated blood directly from the heart to the liver.
Some of the liver's many important functions include:
Production of bile which is stored in the gall bladder and used to digest fats. If the excretion of bile is blocked, the stools become pale and retain fat. As a result, fat-soluble vitamins (vitamins A, D, E, and K) are not properly absorbed and levels of bilirubin, the main component of bile, rises in the blood. Once bilirubin levels reach a certain level, jaundice or yellowing of the skin and eyes occurs.
Synthesis of proteins, including albumin. Albumin is the predominant protein in blood plasma and helps to retain fluid within the blood vessels. The loss of albumin results in fluid shifting from blood vessels to the surrounding tissue. The result is swelling of tissue, a condition called edema.
Production of blood-clotting factors that control bleeding. Loss of clotting factors leads to increased chance of hemorrhage.
Metabolism of hormones and medications, such as estrogen and acetominophen (Tylenol). When the liver is damaged, its ability to metabolize hormones decreases. This can result in changes to estrogen and testosterone levels in the body. Symptoms of these changes include loss of pubic hair and the development of spider angiomas, small clusters of red blood vessels on the skin of the upper body, in both males and females. Men sometimes experience a decrease of testicular size and development of breast tissue (a condition called gynecomastia). A decline in the body's ability to metabolize medications means that normal doses can turn into toxic levels. Therefore, doses of medicines are often reduced for people who have liver disease.
Regulation of glucose levels. Loss of liver cells leads to poorly controlled glucose levels. Glucose levels may soar after eating (hyperglycemia) or fall dangerously low between meals (hypoglycemia). This poor regulation of blood sugar is due to a different mechanism than the mechanisms that lead to diabetes types I and II.
Conversion of ammonia, a by-product of metabolism, into a less toxic form called urea. Inability to convert ammonia to urea results in elevated ammonia levels in the blood. This can result in a condition called hepatic encephalopathy, which is a neurological syndrome characterized by alterations in mental status and behavior. Although acute episodes can be reversible, severe cases of hepatic encephalopathy can lead to coma and death.