Liver Function - Major Functions of the Liver in Human Body
What Is the Liver Function?
Do you know about the most important liver function? It is the largest internal organ and gland. Liver has to perform many complex functions. Function of the liver affect almost every other organ of the body.
Many of these liver functions have got great metabolic significance. The jobs that the organ has to do range from acting as storehouse for different substances to making important secretions. Interestingly, the hepatic secretions are of both endocrine and exocrine nature.
Here follows a brief description of some of the major functions of the liver.
Major Functions of the Liver:
Liver is the organ which receives almost all the nutrients that come from our digestive tract. However, chylomicrons are an exception, i.e. the liver does not process them. Chylomicrons are a type of complex lipids. These are mainly the lymph vessels that transport them across different parts of the body.
Liver processes all the nutrients present in the food we eat. The energy is stored. On the other hand, when necessary, it mobilizes the stored energy for use throughout the body. So in a sense, liver acts like an interface between the circulatory blood and the digestive system.
The liver is a storehouse for large quantities of blood. When the total volume of the blood increases in the body, the liver quickly expands to store it. In other words, it can act like a blood reservoir.
In instances of cardiac failure, there is high pressure in the right atrium of the heart. Such a condition causes back pressure in the liver. This forces the liver to expand. The liver can then store about 500 to 1000 ml of extra blood within its own tissues.
The liver can also supply the body with this extra blood in times of low blood volume in the body.
Synthesis and Storage of Glycogen:
The liver plays a key role in carbohydrate metabolism by converting glucose to glycogen. In this way, it prevents hyperglycemia or high blood glucose after a meal rich in carbohydrate.
Conversion of Glycogen to Glucose:
Liver converts the stored glycogen to glucose and releases it into the blood. This conversion occurs in response to low blood glucose level. So, your body is able to maintain a stable blood glucose level during fasting state and between meals.
Glucose from Non-Carbohydrate Compound:
Sometimes, there are no glycogen reserves left in the body. In such a situation, liver comes to play its role. It can also convert non-carbohydrate compounds such as lactic acid, amino acid to glucose.
Unreasonably high output of hepatic glucose occurs in patients with diabetes mellitus. Consequently, there is disturbance in the functions of the liver. Certain antidiabetic drugs are useful to reduce hepatic glucose output.
Synthesis of Plasma Proteins:
Liver synthesizes various plasma proteins. They include albumin, blood clotting factors, apolipoproteins, angiotensinogen and insulin, etc. The blood clotting factors are: fibrinogen, prothrombin, factors v, vii, ix, x, etc.
Liver replaces the plasma proteins in days to weeks after a major blood loss from the body in case of an accident.
Synthesis of Glycoproteins, Enzymes, etc.:
Functions of the liver also include the synthesis of various important compounds in addition to plasma proteins. Synthesis and secretion of transferrin, globulins and other such compounds also falls under the domain of liver.
Conversion of Ammonia to Urea:
Liver removes ammonia from the blood by converting it to a less toxic compound, i.e. urea. Accumulation of ammonia and other toxins may eventually cause hepatic encephalopathy.
In liver cirrhosis, there is an increase in the blood ammonia to toxic level. This occurs due to disturbance in liver function.
Detoxification of Poisons and Drugs:
One of the functions of liver is to detoxify poisons and drugs. It involves the phase l and phase ll biotransformation reactions. If these poisons and drugs keep on circulating in the blood, they would harm and damage different delicate tissues and organs.
They can also have severe effects on the heart muscles. It will eventually lead to the malfunctioning of this vital organ. So, detoxification of drugs and poisons is an extremely important liver function.
The liver function also includes its serving as a place for the metabolism of lipids. It serves the job of:
- Formation of Ketone Bodies.
- Preservation of cholesterol homeostasis.
- Synthesis and secretion of very low density lipoproteins (VLDL).
- Clearance of High density lipoproteins (HDL), Low density lipoproteins (LDL) and chylomicron remnants.
Metabolizing alcohol to acetaldehyde is another liver function. The excess amount of alcohol is directly toxic to the liver cells. The production of acetaldehyde occurs through the action of the enzyme alcohol dehydrogenase on alcohol.
Interestingly, acetaldehyde is more toxic than alcohol itself. The International Agency for Research on Cancer (IARC) has included acetaldehyde in the list of the Group 1 carcinogens.
Synthesis of Bile:
As one of the functions of the liver, it plays a central role in the synthesis, secretion and metabolism of bile. Bile is a fluid that may vary in color from dark green to yellowish brown. The gallbladder stores and concentrates the bile.
The bile contains bile salts, inorganic salts, fats and bilirubin. This hepatic secretion aids in the digestion and absorption of dietary fats across the wall of small intestine. It is also a major excretory route for lipid-soluble waste products.
Storage of Vitamins:
The uptake and storage of vitamins A, D, B12 and folic acid (a B vitamin) is also a liver function. The body uses these vitamins at the time of need.
Storage of Minerals:
Liver stores certain minerals such as iron and copper. Iron is an essential ingredient for blood production. Most of the body’s iron occurs as a part of hemoglobin and myoglobin. Here hemoglobin is an oxygen carrying protein while myoglobin is the oxygen-binding protein in muscle cells.
On the other hand, copper is a constituent of various proteins and metalloenzymes. In this capacity, the mineral plays an important role in the processes of development, proper growth. It is also useful for the maintenance of heart, brain, bone and other organs of the body.
Liver as a Filter:
The liver function requires it to serve as a filter between the blood that comes from the gut and the blood that circulates in the rest of the body. It clears the bacteria, antigens, damaged cells, proteins, hormones and drugs from the portal circulation.
From the variety of the functions of the liver, it becomes obvious that your body cannot afford any disorder of this organ. Its malfunctioning can have drastic effects on overall health of your body.
It has to perform a great variety of tasks, ranging from the synthesis, storage and secretion to detoxification of harmful substances. Different secretions are of great metabolic importance. The liver function in digestion is also very significant.