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How the Liver Works

Anatomy of the liver

The liver is located in the upper right-hand portion of the abdominal cavity, beneath the diaphragm and on top of the stomach, right kidney, and intestines. The liver, a dark reddish-brown organ that weighs about 3 pounds, has many functions.

Illustration of the anatomy of the digestive system, adult
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There are two distinct sources that supply blood to the liver:

  • Oxygenated blood flows from the heart via the hepatic artery.

  • Nutrient-rich blood flows in from the rest of the body through the hepatic portal vein.

The liver holds about 13 percent of the body's blood supply at any given moment.

The liver consists of two main lobes, both of which are made up of thousands of lobules. These lobules are connected to small ducts that connect with larger ducts to ultimately form the hepatic duct. The hepatic duct transports bile produced by the liver cells to the gallbladder and duodenum (the first part of the small intestine) to aid in digestion.

What are the functions of the liver?

The liver regulates most chemical levels in the blood and excretes a product called bile, which helps to break down fats, preparing them for further digestion and absorption. All of the blood leaving the stomach and intestines passes through the liver. The liver processes this blood and breaks down the nutrients and most foreign substances, such as medications, in the blood into forms that are easier to use for the rest of the body. More than 500 vital functions have been identified as being dependent on the liver. Some of the more well-known functions include the following:

  • Production of bile, which helps carry away waste and break down fats in the small intestine during digestion

  • Production of certain proteins for blood plasma

  • Production of cholesterol and special proteins to help carry fats through the body

  • Conversion of excess sugar or glucose into glycogen for storage. (This glycogen can later be converted back to glucose for energy.)

  • Regulation of blood levels of amino acids, which form the building blocks of proteins

  • Processing of hemoglobin for use of its iron content. (The liver stores iron.)

  • Conversion of poisonous ammonia to urea. (Urea is one of the end products of protein metabolism that is excreted in the urine.)

  • Clearing the blood of drugs and any toxic substances

  • Regulating blood clotting

  • Resisting infections by producing immune factors and removing certain bacteria from the bloodstream

When the liver has broken down harmful substances, they are excreted into the bile or blood. Bile by-products enter the intestine and ultimately leave the body in the feces. Blood by-products are filtered out by the kidneys and leave the body in the form of urine.

Online Source: American Association for the Study of Liver Diseaseshttp://publish.aasld.org/yourliver/Pages/liverfacts.aspx
Online Source: Hepatitis B Foundationhttp://www.hepb.org/pdf/the_liver.pdf
Online Source: National Liver Foundationhttp://www.nlfindia.com/liverZone/biologyAnatomy.asp
Online Source: National Liver Foundationhttp://www.nlfindia.com/liverZone/functions.asp
Online Source: MedLinePlus http://www.nlm.nih.gov/medlineplus/liverdiseases.html
Online Source: Pathogenesis of liver injury in circulatory failure; Hematic blood flow, UptoDate http://www.uptodate.com
Online Editor: Geller, Arlene
Online Medical Reviewer: Bass, Pat F. III, MD, MPH
Online Medical Reviewer: Sather, Rita, RN
Date Last Reviewed: 4/16/2012
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