Anatomy And Physiology

Structure and Function of the Liver



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The liver is not only the largest organ in the vertebrate body but it is also the most complex. It serves a wide variety of functions, such as detoxification and metabolism, some of which are vital functions for the continuation of life. In humans the liver, which is made from cells called hepatocytes, can be seen as a roughly triangular organ of around 1.5kg in the upper abdomen.

The liver is structured into four lobes, each of which is made of lobules. Each lobule sends a vein to the hepatic vein, which takes blood away from the liver. The lobules are also covered in other ducts and blood vessels that take various substances in and out of the liver.

In mammals the organ receives a double supply of blood, with the hepatic portal system providing 70% of the blood and the arterial system providing the other 30% of the blood. Bile, produced in the liver, and necessary to emulsify fats, is drained through the bile ducts and into the duodenum or gall bladder.

The liver has an amazing capacity to regenerate, unlike other organs in the body. Indeed it is estimated that a quarter of a liver can regenerate into a whole one because the hepatocytes begin to undergo mitosis again. It is also protected by a peritoneum, a membrane that minimises friction with other organs.

It is estimated that there are hundreds of possible functions that the liver performs so the following overview is by no means comprehensive. One important function is the storage of glycogen, an important carbohydrate molecule that can be converted back to glucose in response to low blood sugar levels being detected. Another important function is the conversion of foods into different types, such as the conversion of carbohydrates into fats, for example.

Another vital function is the detoxification of many of the harmful compounds found in the body. It can also break down many medicinal compounds, something called drug metabolism. In some cases the product of the reaction turns out to unfortunately be more toxic than the original substance, causing toxication.

Other functions of the liver include, for example, the production of albumin, the synthesising of plasma proteins, the destruction of spent red blood cells, the conversion of ammonia to urea, the synthesis of cholesterol, the storage of useful substances such as vitamins, iron, and copper, and the breakdown of hormones, such as insulin, for example.

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