Introducing the Liver...Part 1

Part one in our liver series, BP starts with giving the liver the once over - what does it do, how does it do it and gives a starting point from which to understand other liver issues such as Hepatitis B, C, Cirrochis, fibrosis etc.

The liver is the largest internal organ. It is reddish-brown, weighs approximately three pounds (in the adult male) and is about the size of a football. It is located behind the ribcage on the upper right side of the abdomen. The liver has the unique ability to regenerate its own tissue-as much as three-quarters of the liver can be lost, and the organ can grow back within several weeks. This allows people who need transplants to receive part of the liver of a living donor. The liver is divided into four lobes; these are in turn composed of multiple lobules, which contain the hepatocytes, or working liver cells. The liver has an extensive blood supply, receiving oxygen rich blood from the hepatic artery. The portal vein delivers blood containing nutrients, toxins, and other substances absorbed from the intestines to the liver. The liver filters this blood, then sends it on to the heart via the hepatic vein.

Functions of the liver
The liver is responsible for some 500 bodily functions. It plays a role in digestion, sugar and fat metabolism, and the body's immune defense. It processes almost everything a person eats, breathes, or absorbs though the skin. About 90% of the body's nutrients pass through the liver from the intestines. The liver converts food into energy, storesnutrients, and produces blood proteins. The liver also acts as a filter to remove pathogens and toxins from the blood. In the developing fetus, blood cells are produced in the liver.

Digestion
The liver plays an important role in the digestion and processing of food. Liver cells produce bile, a greenish-yellow fluid that aids the digestion of fats and the absorption of fat-soluble nutrients. Bile is delivered to the small intestine
through the bile duct; when there is no food to digest, extra bile is stored in a small organ called the gallbladder located beneath the liver.

Byproducts from the breakdown of drugs and toxic substances processed by the liver are carried in the bile and excreted from the body. A person with a damaged liver may experience impaired bile production and flow. When this happens,the body may not be able to properly absorb nutrients. Liver cells also convert heme (a component of hemoglobin that is released when red blood cells are broken down) into bilirubin. When the liver is damaged, bilirubin may build up in the blood, causing jaundice (yellowing of the skin and whites of the eyes).

Metabolism
The liver carries out many metabolic functions, providing the body with the energy it needs. It regulates the production, storage, and release of sugar, fats, and cholesterol. When food is eaten, the liver converts glucose (blood sugar) into glycogen, which is stored for later use. When energy is needed, the liver converts glycogen back into glucose in a process called gluconeogenesis.

The liver regulates the storage of fats by converting amino acids from digested food into fatty acids such as triglycerides; when the body does not have enough sugar, the liver converts fatty acids into ketones, which can be used for fuel. The liver also controls the production, metabolism, and excretion of cholesterol, which is an important component of cell membranes and certain hormones.

Storage
The liver stores several nutrients,
including vitamins A, D, B9 (folate), and B12. It also stores iron and plays a role in converting iron into heme, a component of hemoglobin (the oxygen-carrying molecule in red blood cells).

"The hardworking and often misunderstood liver performs over 500 bodily functions, processing everything that you eat, breathe and absorb through your skin."

Protein Synthesis
The liver synthesizes (builds) several important proteins, including enzymes, hormones, clotting factors, and immune factors. Liver enzymes called amino transferases or transaminases (ALT and AST) break down amino acids from digested food and rebuild them into new proteins needed by the body. When liver cells are damaged, these enzymes can leak out and build up to high levels in the blood; these enzymes can be measured using a simple blood test. Several of the proteins synthesized by the liver are needed for proper blood functioning. These include various binding proteins (which bind and transport substances such as vitamins, minerals, hormones, and fats) and albumin (a protein that helps maintain proper blood volume). Clotting factors produced by the liver include fibrinogen, prothrombin (Factor II), and Factor VII. These enable the blood to clot following an injury; low levels can lead to prolonged bleeding and easy bruising. Other proteins synthesized by the liver include alkaline phosphatase, gamma-glutamyl transferase (GGT), and insulin growth factor.

Detoxification
The liver plays a crucial role in detoxifying substances that are harmful to the body, including alcohol, drugs, solvents, pesticides, and heavy metals. When a person is exposed to high levels of these chemicals, the liver can become overwhelmed. Toxins are delivered to the liver by the portal vein. The liver processes these chemicals and excretes them in the bile. The liver also processes and excretes toxic byproducts of normal metabolism (such as ammonia) and excess hormones (in particular, sex hormones such as estrogen). Many drugs-including common over-the-counter drugs such as acetaminophen (Tylenol), most anti-HIV drugs, and certain herbal
remedies-are processed by the liver and can cause liver damage.People should be especially cautious about combining multiple drugs or herbs. If the liver is damaged it may not be able to break down and excrete drugs efficiently, which could potentially lead to dangerously high blood levels and intensified side effects.

Liver Damage
Chronic hepatitis C or B, heavy alcohol use, and other factors can lead to serious liver damage. Given how many vital functions the liver performs, it is not surprising that liver injury can have an affect on almost all body systems, including the digestive, endocrine, cardiovascular, and immune systems. As the liver sustains damage, normal liver tissue becomes fibrous (fibrosis), fatty (steatosis), and scarred (cirrhosis). If the liver becomes too heavily damaged, it isno longer able to carry out its normal functions. In compensated cirrhosis, the liver is scarred but can still function relatively normally. In decompensated cirrhosis, the liver has sustained so much damage that it is unable to function properly. Scar tissue may block the normal flow of blood through the liver, causing blood to back up. This can lead to portal hypertension (high blood pressure), the development of varices (stretched and weakened blood vessels) in the esophagus and stomach, and internal bleeding.

People with severe liver damage may also develop ascites (fluid accumulation in the abdomen), edema (swelling, especially in the legs and ankles), and kidney damage. If the liver is unable to filter out toxins and metabolic by products such as ammonia, these chemicals may build up in the blood, leading to impaired mental functioning, personality changes, and (in severe cases) coma. People with long-term liver damage may also develop liver cancer.