The liver, gall bladder and pancreas form an important part of the body’s digestive system. The liver weighs about 1500 grams, and is tucked up under the ribs in the right, upper part of the abdominal cavity. Blood coming from the intestinal system, charged with the products it has absorbed, arrives at the liver via the portal vein, and pours through the liver at the rate of 1.5 liters a minute. An important function of the liver is to process this blood as it passes through.
Once the food has been absorbed by the blood vessels of the small bowel, it is carried via the portal blood system to the liver. Here much of it is stored. If certain unwanted products or poisons are present, these are dealt with by a process of detoxification (rendered harmless to the system), then excreted. Many processes are carried out by special chemicals or enzymes manufactured by the liver. Volume is added to the blood from the water reabsorbed by the large intestine.
The augmented blood supply proceeds from the liver to the heart, and the general circulation then accumulates the new volume of food and fluid. So the final products of the food digestion and absorption are injected automatically into the general blood supply of the system.
In the last section we saw how the blood was augmented in its supply of oxygen (and relieved of its unwanted toxic supply of carbon dioxide and other unwanted gases) through the respiratory system. Now, the blood receives other factors – food and water. In other words, its capacity to supply the body with essential nutrients is suddenly increased. At the same time, certain unwanted by-products are eliminated through the bowel system.
Another vessel, called the hepatic artery supplies the liver itself with blood. Collectively, the blood leaves the liver through the hepatic vein, to go on to the heart and the general body circulation.
The liver has many important functions. It manufactures bile salts, which are important in assisting the absorption of fats from the bowel. It produces an important number of proteins (such as transferring, which combines with iron) that bind with other elements and assist both absorption and their subsequent use. It also produces the proteins that are essential for blood clotting.
Carbohydrates that have been absorbed in the form of glucose and galactose are converted into glycogen, a form in which they may be stored. The liver is able to break down fat to produce energy. It also helps break down certain hormones, drugs and diuretics to a form in which they are finally eliminated from the body.
It is important to note that the presence of certain other drugs can impede this action. That is why some patients on certain drug regimens fail to respond when given other medicinal drugs, for the first one affects the action of the second one via the enzymes. A well-known case is the effect of the anti-TB drug rifampicin. This may negate the effect of the oral contraceptive pill. Several women taking both forms of medication have subsequently become pregnant.
This acts on the enzyme system of the liver. Many enzymes (special chemicals that have a specific duty) are manufactured by the liver, and they play an important part in drug metabolism, and the breakdown and use of the drugs.
The liver is an important storehouse for many substances, such as iron, folic acid and vitamin B12, all essential in the normal production of blood. The amount of B12 stored in the liver is sufficient to supply the bodily needs for three years, even if no further amounts are ingested, it is claimed.
There arc many liver-function tests that can be carried out to ascertain that the organ is operating correctly. In recent years enzyme levels have come to the fore. It has been found that the production of chemicals called enzymes can be affected by various diseases, and these levels can readily be measured. This often assists in diagnosis of certain diseases.
Doctors now readily order such tests as the SGOT, the SGPT, the Sorbitol dehydrogenase, the Lactic dehydrogenase, and many others. They all play a role in assisting more accurate diagnoses.