The Functions of the liver in the human body are numerous. The liver is an organ in the body that is located in the right upper part of the abdomen called the right hypochondriac region. The Liver is an important organ that is needed for survival. This article aims to list the liver functions in the human and explain in details each function of the liver. When there is liver disease, the functions of the liver become deranged; such abnormal function of the liver can be tested in the laboratory using the Liver function tests which are various tests carried out in order to assess the function liver and integrity of the structure because there is no single liver function test can assess all the different functions of the liver.
Functions of the Liver in the human digestive system
- Protein metabolism
- Carbohydrate metabolism
- Lipids metabolism
- Formation of bile
- Drug inactivation
- Hormone inactivation
- Immunological function of the liver
Liver function in Protein Metabolism
The liver plays a major role in protein metabolism. Metabolism involves the breakdown of nutrients and also the build up of nutrients. The Liver functions in protein metabolism by making proteins from amino acids; it does this when the intestines break down protein when we eat such as meat or beans; when the meat is broken down, the intestines absorbs it into the blood in the form of amino acids (the smallest components that make up proteins) and it is taken to the liver. The liver then forms the necessary type of protein the body needs. Examples of proteins produced or formed by the body include albumin and clotting factors.
List of Proteins produced by the Liver
- Albumin: a major protein in the blood involves in maintaining oncotic pressure in the blood and transport of pigments (bilirubin) and other substances such as drugs, hormones and fatty acids. It transports substances that are not soluble in blood. Reduced synthesis of Albumin occurs in chronic liver disease and also in protein energy malnutrition such as Kwashiorkor.
- Transport proteins such as Transferrin, ceruloplasmin, alpha feto protein, alpha 1 antitrypsin,
- Clotting factors involved in coagulation such as Protein C, Protein S, Factors V, VI, VII, IX, X, XIII and Fibrinogen.
Function of the Liver in Storage
The liver stores Vitamins such as Vitamin A, Vitamin D and Vitamin B12 in large amounts and vitamin K and folate in smaller amounts. Other minerals such as iron (stored as ferritin), copper and hemosiderin are also stored in the liver. The liver also stores carbohydrate in the form of glycogen which is then broken down during starvation.
Liver function in Carbohydrate metabolism
When there is excess carbohydrate, it is converted to glycogen by the liver and stored. The liver stores about 80g of glycogen. During starvation or fasting, the liver breaks down the glycogen through a process known as Glycogenolysis. The liver can also make glucose available for the body during lack through a process called Gluconeogenesis (which is the formation of glucose from non-carbohydrate source such as amino acids, lactate, glycerol or pyruvate).
Function of the liver in Fats Metabolism
The liver produces Cholesterol, Very low density lipoproteins (VLDL) and High density Lipoproteins (HDL). It is also involved in the breakdown of fats during starvation.
Production of Bile
The liver synthesize bile and secrets it into the gall bladder. The bile helps in the digestion and absorption of fats, without which fats cannot be absorbed. The liver also produces bilirubin in the kupffer cells from the breakdown of red blood cells.
Hormone and Drug Inactivation
Hormones are chemical secretions produced from ductless glands to target organs that may be distant to the area of production. When hormones act on organs, they need to deactivated, if not, they continue to act which may be a problem to the body. When hormone actions are done, they are inactivated in the liver.
Examples of hormones inactivated in the liver
- Parathyroid hormone
- Growth hormone
Drugs are also metabolized in the liver. Some drugs need to be broken down to the active forms in the liver while others are inactivated in the liver. Fat soluble drugs are converted to water soluble drugs in the liver to enable their excretion in urine and bile. Alcohol is also metabolized in the liver.
Immune function of the Liver
The liver acts to protect the body against infections and inflammation through the reticuloendothelial system of the liver. This immune function is carried out by macrophages in the liver known as Kupffer cells. These cells produce chemicals that control infection and mediate inflammatory process such as Tumor Necrosis Factor (TNF), Interleukins, collagenase and lysosomal hydrolases. These chemicals produced attack the invading organism without even spreading to other immune systems of the body that may trigger wide spread immune response which may even turn out to become harmful to the body.
Major Functions of the Liver
Of all the liver functions mentioned above, the major liver functions include Metabolism (of carbohydrates, fats and lipids), Excretion of Waste products (in the bile), and storage of vitamins and minerals.