Components and function of the blood dkg

Leukemia, often called "blood cancer," is a malignant disease of the white blood cells. It starts in the bone marrow, the body's blood-forming organ. From there, the disease can affect all organs of the body.

What is the function of the blood?

Depending on body weight, 4 to 6 liters of blood flow in the veins of an adult human being. Blood is made up of different components, each of which has an important function in the body. The correct composition of the blood is an important condition for the well-being and health of a person.

The components of the blood

About half of the blood consists of blood plasma, a yellowish fluid composed primarily of water and various proteins. The other half of the blood is cells, called blood cells. There are three types of blood cells:

– the red blood cells (erythrocytes) – the white blood cells (leukocytes) – the platelets (thrombocytes)

This vital fluid fulfills a variety of tasks: It supplies organs and ties with oxygen and nutrients via the bloodstream, it "disposes" of carbon dioxide and other "waste products" from the body's cells, it serves to regulate heat as well as distribute hormones and many other substances. Specialized cells and proteins of the blood serve to defend against pathogens and protect against blood loss after an injury.

The red blood cells

Red blood cells, also called erythrocytes, are the most numerous cells in the blood. They make up 99 percent of all blood cells.

The main task of red blood cells is to transport vital oxygen, which is absorbed in the lungs, through the blood vessels to the organs and ties of the body. Red blood cells fulfill their task through the red blood pigment they contain, hemoglobin. If red blood cells are not present in sufficient quantity or – due to a lack of red blood pigment, z. B. due to a lack of red blood pigment, e.g. iron deficiency, they do not function properly, this is known as anemia. "Blood-deficient" people often have strikingly pale skin. Since the body is no longer supplied with sufficient oxygen, they also suffer from symptoms such as fatigue, weakness, shortness of breath, reduced performance or headaches.

The white blood cells

The white blood cells, known as leukocytes, are present in the blood of healthy people only in small quantities compared to other blood cells, because they make up only 1 percent of all blood cells.

The leukocytes are essential components of the immune system. They are, so to speak, the "policemen of the blood". Their most important task is to recognize invaders such as bacteria, viruses or fungi and make them harmless. This happens in 3 ways: Firstly, through the direct uptake of such "harmful substances" into a cell, secondly, through the production of so-called antibodies, proteins that can recognize and bind foreign tie, and thirdly, through cells that can specifically attack and destroy the invaders. The number of white blood cells can increase sharply within a very short period of time when there is an "emergency". This ensures a rapid fight against pathogens.

The white blood cells can be divided – according to appearance and function – into five groups: Into so-called granulocytes, lymphocytes, monocytes, eosinophils and basophils. Granulocytes are the most abundant, accounting for 60-70 percent of the total; 20-30 percent are lymphocytes, 2-6 percent are monocytes, and 1-6 percent each are eosinophils and basophils. The five types of cells have different methods of fighting pathogens; they complement each other:

Granulocytes – Leukocytes – so called because of the granules in their cell fluid – remain in the blood for only a few hours after their formation before they migrate to their sites of action, the ties, and here in particular the mucous membranes. There they are mainly responsible for the defense against bacteria, but also against viruses, fungi and parasites (z.B. worms). granulocytes are so-called scavenger cells. They surround the invaders and digest them. This process is called phagocytosis. Dead body cells are also eliminated in this way. Granulocytes are also involved in allergic reactions. Inflammatory reactions as well as involved in the formation of pus.

The Lymphocytes are small white blood cells, 70 percent of which are found in the lymphatic ties. Lymphoid ties include lymph nodes, spleen, pharyngeal tonsils and the thymus gland. Lymphocytes play a central role in the defense system because they can specifically recognize and eliminate pathogens. An essential role they play z.B. in case of viral infections. The lymphocytes "organize" the use of the granulocytes and produce so-called antibodies. These are small protein molecules that attach themselves to the pathogens and thus make them recognizable as "enemies" for the scavenger cells. Lymphocytes also recognize and destroy body cells infected by viruses and tumor cells.

The Monocytes are the largest cells in the blood. They remain in the vascular system for only 1 – 2 days and then migrate to various organs, where they are transformed into resident macrophages. The macrophages are, as the name suggests, also called the "big scavenger cells" of the defense system. They ingest and digest minute organisms, foreign bodies and tie debris. In addition, they present parts of the eaten and digested organisms on their surface and in this way stimulate the lymphocytes for immune defense.

The Eosinophils play an important role in the defense against parasites.

The function of Basophils lies mainly in the triggering of allergic reactions.

If the number of white blood cells in the blood is reduced or they are not functional, invaders can no longer be fended off effectively. The organism is then susceptible to infections.

The blood platelets (thrombocytes)

Platelets play an important role in blood clotting and thus in hemostasis: they ensure that, in the event of an injury, the walls of the blood vessels are sealed within a very short time, and the bleeding stops. A too low platelet count manifests itself, for example, through nose or gum bleeding as well as minor skin bleeding. Even slight jolts can lead to bruising, and bleeding into internal organs can also be the result.

The site of blood formation

All blood cells are formed in the bone marrow. Bone marrow is a reticular tie with a large blood supply that fills the cavities inside bones. Red and white blood cells as well as platelets develop there from common precursor cells, the so-called stem cells of hematopoiesis. The various blood cells mature in the bone marrow and, once functional, are released into the bloodstream. The only exception is a part of the lymphocytes, a subgroup of the white blood cells: they do not mature in the bone marrow, but only in the lymphatic tie in order to fulfill their specific function there.

Mature blood cells have a relatively short life span. For platelets and granulocytes, it is only 8-12 days; for red blood cells, it is as long as 120 days. The consumption of blood cells is therefore immense: over two million blood cells perish every second. The bone marrow must therefore constantly produce new cells so that the blood can fulfill its vital functions. In healthy people, this system works so perfectly that as many new cells are produced as have perished. Overproduction" is prevented by certain inhibitory factors.

Michl Marlies: Basics Hematology, Urban and Fischer Publishers 2010

Last content update on: 21.03.2017

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Source: © Natalia Bratslavsky –

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