Basics about the liver

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To understand how hepatitis C (HCV) affects the liver, it is helpful to know the basics about this amazing, multifaceted organ. Aside from the skin, the liver is the largest organ in the body. It is reddish in color and is located behind the ribcage on the right side in the upper part of the abdomen. It is one of the most complex organs in the body, performing over 500 chemical processes and producing over 160 different proteins. The liver is about the size of a football (3.3 lbs) and capable of regenerating itself. If you lost a portion of your liver (as much as three quarters), it would regenerate itself within about a month. Because of its ability to regenerate, part of the liver can be taken from a living donor for transplantation. 1,2

The structure of the liver

The liver is made up of four sections called lobes, each in turn made up of lobules. The lobules contain the cells that do the work of the liver. There are several blood vessels that carry blood to and from the liver. These include the main (hepatic) artery, that carries oxygen-rich blood to the liver from the heart and the portal vein, which carries oxygen-poor blood from the intestines. The blood that comes from the portal vein carries a range of substances, including nutrients and toxic substances. It is the job of the liver to filter out these substances and send blood on to the heart via the hepatic vein.1

Liver functions

We require a healthy liver for survival. The liver carries out a wide range of functions, including1,2:

  • Aids in digestion
  • Production of proteins (used to build and maintain the body)
  • Storage and release of sugar as glycogen
  • Production of hormones
  • Removal of toxic substances that enter the body
  • Metabolism of foods and other substances
  • Filtration of blood

Digestion and metabolism. The liver plays a role in metabolizing almost everything we take in, including what we eat, breathe, and even substances that we absorb through our skin. Almost all (about 90%) of the nutrients that are processed though the intestines (large and small) are filtered through the liver. The liver also plays an important role in transforming carbohydrates into glucose (the key source of energy for the body) and storing that glucose in the form of glycogen.2

Liver cells (hepatocytes) produce the greenish-yellow fluid called bile that plays a pivotal role in the breakdown and absorption of nutrients (protein, fat, and carbohydrates). It controls the storage of fat, by transforming amino acids into fatty acids. The liver also stores several key vitamins and minerals, including vitamins A, D, B9, and B12 and iron. The liver takes part in transforming iron into heme, the portion of red blood cells that carries oxygen. 2

Blood filter. The liver serves as a filter for the blood, removing toxic substances, as well as bacteria. Cells in the liver called Kupffer cells are so efficient at trapping bacteria that come from the intestines that only 1% of bacteria in blood entering the portal vein makes it through the liver into systemic circulation.

Because of its ability to expand, the liver also serves as a reservoir for blood. The normal blood volume of the liver (450 milliliters including blood in its veins and sinuses) comprises about 10% of the blood volume of the body. When pressure builds in the heart (as happens during heart failure), the liver can expand to accommodate up to a liter of extra blood. 2

Protein synthesis. The liver synthesizes a range of important proteins in the body, including enzymes, hormones, clotting factors, and immune system proteins. Two key liver enzymes called transaminases (alanine transaminase [ALT] and aspartate transaminase [AST]) breakdown digested food into amino acids, which they use to form new proteins that carry out various functions throughout the body. For instance, the liver synthesizes blood proteins used in clotting, such as fibrinogen, prothrombin, and the protein albumin, that helps maintain appropriate blood volume. When high levels of ALT and AST are found in blood, it is a sign that the liver is not functioning normally. 2

Filtration. The liver plays a key role in filtering out harmful and toxic substances that enter the body through eating, breathing, and skin absorption. Included among these are heavy metals, pesticides, toxic chemicals, drugs, and alcohol, as well as chemicals that the body produces, including ammonia and extra hormones. Most of the substances that enter via the digestive tract come to the liver via the portal vein, which carries blood and nutrients from the intestines. Normally, the liver processes harmful substances and gets rid of them in bile. However, when too much of a substance enters the body, such as with excessive alcohol consumption, the liver can become overburdened. Certain drugs, supplements, and herbal products can pose a danger to the liver. This is more likely to occur when these substances are taken at too high a dose, for too long or when taken with other drugs or substances For example, when Tylenol (acetaminophen) is taken too often or at too high a dose, and especially when it is taken with alcohol, it can harm the liver. 2

To make sure your liver stays healthy, it is necessary to tell your doctor about all drugs (prescription or non-prescription, over-the-counter) and supplements (natural and herbal products, vitamins, and minerals) that you are taking.

HCV and the liver

Cirrhosis is a serious condition that may occur with HCV, in which fibrosis (damaged liver tissue) is replaced by severe scarring. The early symptoms of cirrhosis include fatigue, nausea, stomach pain, decreased appetite and weight loss. Severe cirrhosis has many complications, including edema (fluid build-up in the ankles and legs), ascites (fluid accumulation in the abdominal cavity), esophageal varices (enlarged, fragile blood vessels in the esophagus), and hepatic encephalopathy (mental confusion caused by high level of toxins in the blood). Having cirrhosis can increase a person’s chances of developing liver cancer (sometimes called hepatocellular carcinoma). Approximately 1 in 50 people with cirrhosis develop this type of cancer. 3

Studies have found that up to 50% of people with chronic HCV infection eventually develop cirrhosis.4,5 In a person with chronic HCV, cirrhosis typically develops gradually. About 20% to 30% of people with chronic HCV infection will develop cirrhosis over a 20- to 30-year period. 3

Learn more about how HCV affects the liver.

view references
  1. McKuskey R. In: Boyer TD, Manns MP, Sanyal AJ, eds. Zakim and Boyer's Hepatology: A Textbook of Liver Disease. 6th ed. Saunders Elsevier. Philadelphia, PA; 2012:3-19.
  2. Hall JJ. Chapter 70: The liver as an organ. In: Guyton and Hall Textbook of Medical Physiology. 12th ed. Saunders Elsevier. Philadelphia, PA; 2010: 837-842.
  3. . Chopra S. Clinical manifestations and natural history of chronic hepatitis C virus infection. Uptodate. Di Bisceglie AM, Bloom A, eds. Accessed at: www.uptodate.com. 2014.
  4. Tong MJ, el-Farra NS, Reikes AR, Co RL. Clinical outcomes after transfusion-associated hepatitis C. N Engl J Med 1995;332:1463-6.
  5. Yano M, Kumada H, Kage M, et al. The long-term pathological evolution of chronic hepatitis C. Hepatology 1996;23:1334-40.
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