What Is the Liver's Job?

The liver, located below the diaphragm in the right side of the abdomen, weights approximately 3 lbs. and is the largest internal organ in the human body. The liver is essential for survival, works 24 hours a day and performs hundreds of functions. The liver's key roles are related to synthesis, storage, digestion, breakdown of naturally produced but harmful substances and detoxification.

Synthesis

• The liver synthesizes amino acids, the building blocks for proteins; hormones such as thrombopoetin, which regulates platelet production, and angiotensin, which regulates blood pressure; cholesterol and lipids; albumin, a major component of blood serum; and coagulation factors. The liver also plays a crucial role in carbohydrate metabolism by synthesizing glucose and transforming it into its storage form called glycogen.

Storage

• The liver stores glycogen, iron, copper and vitamins A, D, E and B12. The liver's glycogen reserve is the first line of defense against falling blood glucose levels. When needed, the liver converts glycogen into glucose and releases glucose into the blood stream. In a similar way, the liver releases iron, copper and vitamins into the blood stream when needed.

Digestion

• The liver produces and secretes bile, a thick greenish-yellow fluid stored in the gallbladder between meals and emptied into the intestinal system by the common bile duct for digestion. Bile helps the body absorb and digest lipids, fats and fat-soluble vitamins. Bilirubin from red blood cell decomposition, used hormones, excess cholesterol and drug metabolites are all secreted into bile for elimination from the body in feces.

Breakdown

• The liver breaks down or neutralizes naturally produced substances that are harmful to the body. For example, ammonia is produced naturally in the digestion process, but too much ammonia in the body causes brain swelling and can be fatal; the liver converts ammonia into urea for excretion. The liver also breaks down hemoglobin in aging red blood cells and turns hemoglobin into bilirubin. Some bilirubin is excreted from the body but most is recycled. Disorders of hemoglobin metabolism cause jaundice.

Detoxification

• The liver plays an important role in detoxifying the body. The liver removes harmful foreign substances and toxins from the body by metabolizing and filtering these substances from the blood, such as drug metabolites, medication overdoses and alcohol. The liver is injured when these substances are consumed in amounts overwhelming to the liver. For example, heavy alcohol consumption causes fatty liver disease, alcoholic cirrhosis, where scar tissue replaces normal tissue in the liver, and alcoholic hepatitis, which is inflammation of the liver.