Body talk

Liver: The complex chemical factory and storehouse

By now we have learnt about a number of organs in the human body. Today, we will be discussing the largest and heaviest internal organ of our amazing body. Can you guess what it is? No machine could do its work. Well.. the answer is the liver. Without a liver, life would be impossible. So, as the poet Hood wrote: "Is life worth living? - it depends on the liver".

The liver, smooth, cone-shaped, red-brown and rubbery, is the largest and heaviest internal organ. Do you believe it weighs around 3.5 lb.(1.6 kilos)? Situated in the upper right part of the abdomen, where it is partly protected by the rib cage, the liver contains 300 billion cells.

The liver is the centre of your metabolism, a complex chemical factory and filter that controls the body's absorption of food. It carries out more than 500 separate processes concerned with regulating all the main chemicals in blood and many other life-supporting functions. Despite its complexity, the liver is remarkably resilient. It can keep going even if it loses as many as 80 per cent or even 90 per cent of its cells through disease or surgery.

The liver is divided into a large right lobe, which is subdivided into three sections, and a smaller left lobe that tapers towards a tip, which is in contact with the stomach, intestines and oesophagus.

Each lobe contains 50-100,000 small segments known as lobules. Each of these, in turn, contains hundreds of cells arranged like fine spokes radiating out from the central vein in a network of blood channels called sinusoids.

These act like the holes in a sponge, carrying oxygenated and nutrient-rich blood to the liver cells. Unlike any other organ, the liver has a double blood supply. Oxygenated blood from the heart to the liver, which needs about a quarter of the heart's total output - 1.75 pints (1 litre) a minute - comes via the hepatic artery. This subdivides into many branches within the liver to provide oxygen to all its cells.

The portal vein also feeds the liver with blood. It carries nutrients from digested food such as fats and glucose from the intestines and spleen, which the liver either uses or stores, depending on the body's needs.

All the liver's blood, carrying carbon dioxide and other products, drains into the hepatic veins. Bile, which assists digestion by processing fats in the small intestine and neutralising stomach acid, leaves the liver through a network of tiny bile ducts. These fuse to form the right and left hepatic ducts, which themselves fuse and carry bile to the gallbladder.

Raw materials for the human body, as with a household or a factory, both, provide energy and repair or enhance the fabric. Also, some items need to be stored for future use, or discarded as waste. The liver is central to all the many processes involved. After a meal, in a turmoil of activity, this chemical factory of the body acts as a manufacturer and supplier, a depot and a waste disposal unit, a cleanser and protector, a regulator and facilitator.

Maintaining a healthy liver

The liver largely looks after itself and suffers little wear and tear. As the liver has a remarkable ability to produce new cells to replace its own diseased or damaged, surgeons can remove a section of a healthy liver from an adult and transplant it into a child who has a diseased liver. The child's new liver, (if not rejected by the body) will grow as the child grows.

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What the liver does:

* It aids digestion by helping the absorption of fat and vitamins.

* It distributes nutrients in food.

* It helps to cleanse the blood by removing toxins.

* It produces important proteins for the blood, notably albumin (which regulates the exchange of water between blood and tissues).

* It provides coagulation factors essential for clotting blood after injury.

* It supplies globin, a constituent of oxygen-carrying haemoglobin in the blood.

* It makes cholesterol and proteins which help carry energy-supplying fats around the body.

* It stores glucose that the body does not need immediately in the form of glycogen, which it converts back to glucose and releases into the bloodstream when needed.

* It regulates the blood level of amino acids, chemicals which are the building blocks of proteins.

* It protects the body by removing bacteria and neutralising toxins that would otherwise accumulate.

* It filters many chemical substances and waste products from the blood.

* It secretes up to two pints (1.14 litres) of bile daily which remove waste products - food and water contain thousands of non-nutrients that require constant liver processing and detoxification.

* It banks vitamins A, B, D, E, K and others for release into the bloodstream when supplies get low.

* It helps to retire old blood cells.

* It turns sugars and fats into protein, and vice-versa, maintaining the blood sugar level.

* It regenerates itself - it creates new cells as old or damaged ones die off.