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Liver

 

Liver tumour

 

In the medical field, one generally distinguishes between primary and secondary malignant tumours (metastases). The primary malignant liver tumour arises from the liver cells itself or from the cells of the biliary pathways which are situated next to the liver tissue. The secondary tumours, mostly referred to as metastases, are scattered cells of a malignant tumour, which emerged from another organ, for example the large intestine, rectum or even the kidneys.

 

How does the liver function?

The liver, serving as a blood filter and being located between the bowel and the rest of the organism, takes care of the most various and complex assignments in the metabolism of the human being. It produces important substances (blood clotting agents and cholesterol), keeps the equilibrium of many substances (fat, sugar, hormones, vitamins) and helps to discharge medicaments, catabolic products, and toxicants from the body. Besides, it is the biggest gland and is responsible for the production and delivery of bile, and it thus plays an important role in the digestion of fat in the bowel. Consequently, a restriction of the function of the liver tissue, caused by tumours or inflammations, results in more or less grave after-effects: the glycometabolism may be upset (hypoglycaemia), proteins are produced only insufficiently (disorder of blood coagulation, hydro-abdomen), and the bile salts and pigments are insufficiently discharged (itching and yellow colouring of the skin). One of the most important abilities of the liver is its enormous regenerative capability. If the liver has to be partly excised and considerable quantities of liver tissue are removed (maximum 75%), a compensatory growth of the remaining liver will be observed after some time. There is an increase of liver cells under the influence of messenger substances in this process, but there is also an obvious enlargement of the remaining liver cells.

Where is the liver located and what is its structure? 

With an average weight of 1.5 kg and a capacity of three litres, the liver is one of the biggest and most important organs. Three quarters of it are found in the upper abdomen on the right side, and its form resembles an oblique three-sided pyramid. On top, it is connected to the diaphragm, and it thus lowers when a person exhales. The doctor takes advantage of this if he wants to palpate the lower rim of the liver and feel its outlines. At the lower part of the liver, the gall bladder and the lower caval vein are so deeply embedded in its tissue that there is an asymmetrical external partition into a small part to the left and a big one to the right. This external view, however, contrasts strongly with the very symmetrical inner structure of the liver, which is subdivided into eight sections as shown by Claude Couinaud. The internal symmetry results from a regular organisation of one vein, one artery, and one bile duct in each of the eight sections. These vessels receive supply from the hepatic portal located at the bottom of the liver. It is there that the great supplying vein and artery enter the liver. The vein carries along oxygen-deficient blood, which is however rich in protein, from the stomach and the bowel. It is filtered by the liver and detoxicated in the process. The portal vein divides into a left and a right branch right after entering the liver. Both branches go on dividing and form the portal vascular tree of the liver. The artery supplies the liver tissue with blood rich in oxygen. It also branches off various times, thus forming the arterial vascular tree of the liver. There is a kind of an interdependent steering mechanism between the two: in case of a very serious disease of the liver with impairment of the blood supply in one of the two vessels, the other vessel will compensate it. After having passed the liver, the blood flows via the third vascular tree, the big liver veins, into the lower caval vein and towards the heart. At the same time, the bile produced in the liver cells is transported from around the hepatic porta in the opposite direction and partly stored in the gall bladder or discharged into the duodenum for the digestion of food. This complex inner structure still takes even highly qualified surgeons to their limits. This is especially the case if they try to save a small part of the liver intensively infiltrated by a tumour, so that the patient receives the best surgical therapy possible.

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