Synonyms
Liver flap, liver cell, liver cancer, liver cirrhosis, fatty liver Medical: hepar
Definition
The liver is the central metabolic organ of humans. Its tasks include the food-dependent storage, conversion and release of sugars and fats, the breakdown and excretion of endogenous and medicinal toxins, the formation of most blood proteins and bile, and numerous other tasks.
- Thyroid cartilage larynx
- Trachea (windpipe)
- Heart (Cor)
- Stomach (Gaster)
- Large intestine (colon)
- Rectum (rectum)
- Small intestine (ilium, jejunum)
- Liver (Hepar)
- Lung
- Right lobe of the liver
- Left lobe of the liver
The blood supply to the liver is a special case in the human body.
A total of 1.5 liters of blood per minute flows through it, which corresponds to a relative proportion of 25% of the body’s total blood. Three-quarters of these 1.5 liters come from the veins of the gastrointestinal tract, which join together to form a new vein (V. portae, portal vein). In the organs of the digestive tract, the blood has already released its oxygen.
As a result, this part of the blood cannot supply the liver cells with oxygen. This function is performed by the remaining 25% of the liver blood, which supplies oxygen-rich blood from the aorta via the hepatic artery (Arteria hepatica propria). What is the purpose of all this?
The blood, which flows through the gastrointestinal tract, absorbs all substances that have been supplied to the body with food. These can be both desirable substances (e.g. proteins, sugar (carbohydrates), vitamins) and undesirable substances (toxins, drugs). It is useful for the body to first pass the mixture through the liver and filter it there to protect the other organs.
The sensible substances are at least partially buffered for bad times, the dangerous substances are detoxified as much as possible. And since the body needs energy for all these processes, the liver must be supplied with oxygen. This explains why two functionally different vascular systems reach the liver.
In the liver, the vessels run through the above-mentioned connective tissue fibers and continue to divide up. The end point for the branching are the corners of the smallest liver unit, the hexagonal liver lobules. This is where the two previously separated blood streams mix.
From here, the mixed blood continues to flow along predetermined paths to the center of the liver lobules. Like all blood vessels in the body, these pathways, also called sinusoids, are lined by special cells (endothelial cells), but in the case of the liver they are much less dense. Between the endothelial cells there are always larger gaps so that the blood plasma (cell-free part of the blood) can reach the actual liver cells as closely as possible.
In the middle of the liver lobule there is now a kind of collection vessel, the so-called central vein. It leads the blood, which has now been completely cleaned from the liver, out of the liver lobule. The individual central veins continue to unite until they join outside the liver to form a vena hepatica, which in turn opens into the inferior vena cava after a short distance.
Special cells, the copper star cells, are located in the blood vessels of the liver lobules. They belong to the food and defense cells that remove old proteins, red blood cells and also microbial pathogens (bacteria) from the blood. Another type of cell, the so-called Ito cells, has the task of storing fat-soluble vitamins (mainly vitamin A). They are also the origin of the pathological proliferation of connective tissue in liver cirrhosis.