Diseases

Blood - What is it?

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blood is a vital liquid for the body. It is thicker than water and feels a bit sticky. The blood has a temperature of about 38 ° C, which is about one degree more than the body temperature. The amount of blood depends mainly on the size and weight of a person. Read more about the tasks and composition of the blood as well as blood donation!

Article overviewBlood - What is it?

  • Tasks of blood
  • Blood, whole blood, plasma
  • Which and how many blood types are there?
  • Blood donation and blood transfusion

Tasks of blood

Blood has several vital functions: it transports oxygen, nutrients, hormones and enzymes to the body's cells and absorbs waste and carbon dioxide, which is excreted through the liver, kidneys, intestines or exhaled through the lungs. The blood also helps keep certain levels in the body constant, such as body temperature and pH.

In addition, certain blood cells and coagulation factors protect the body from major blood loss: In an injury, they form blood clots and close the injured vessel. White blood cells and messenger substances also fight off pathogens.

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Blood, whole blood, plasma

In the body of an adult usually circulate five to six liters of blood. This is what doctors call whole blood. Blood cells make up around 45 percent of whole blood. The remaining 55 percent are liquid blood plasma. It consists mainly of water. Among other things, it contains various blood proteins as well as blood sugar, vitamins and other substances.

Blood serum is the plasma without the blood coagulation substance fibrinogen.

Most blood cells arise in the bone marrow. Here, the various blood cells mature from the so-called stem cells via a series of precursors.

Red blood cells: The red blood cells (erythrocytes) contain the red blood pigment hemoglobin. In the lungs, oxygen is bound to the hemoglobin and transported to all body cells. In exchange, the red cells from the cells take up carbon dioxide and transfer it to the lungs, where it is exhaled. Erythrocytes look like under the microscope like small slices dented above and below - similar to some candies. They are very flexible and can squeeze into the smallest blood vessels. Their lifespan is around 120 days.

White blood cells: White blood cells (leukocytes) protect the body from foreign invaders. They recognize foreign cells and tissues and destroy bacteria, viruses and other pathogens. Leukocytes can be divided into several subgroups, for example the granulocytes and lymphocytes.

platelets: Platelets (platelets) are much smaller than red blood cells and contain no nucleus. They have an important role in blood clotting: If a blood vessel is injured, platelets from the inside of the injured vessel wall and attach to each other. This quickly creates a blood clot, which closes the injury provisionally. Thrombocytes usually live only five to nine days.

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Which and how many blood types are there?

Every human being - due to his genes - has a specific blood type with specific characteristics. Therefore, blood can not be transmitted freely from person to person. Blood experts know about 150 different blood group systems. However, only a few of them have medical significance. The most important are the ABO blood group system and the rhesus system.

After this ABO blood group system There are mainly four blood types: 0, A, B and AB. In Central Europe, most people have either blood group 0 or blood group A (each about 40 percent of the population). The remaining people have blood group B or (rarely) the group AB.

The Rhesus (Rh) system This is so because the antigens that characterize the particular blood group were discovered in the blood of rhesus monkeys. Various antigens (features on the surface of the cells) play a role in the rhesus system. The most important is the D-antigen. People whose red blood cells have the D-antigen are "rhesus-positive", those without the D-antigen are called "rhesus-negative." In Central Europe, about 85 percent of people carry the trait D-antigen and are rhesus-positive.

Especially for pregnant women the rhesus factor plays an important role. If a Rh-negative mother carries a Rh-positive baby in the stomach, then her organism produces antibodies (antibodies) against the D-antigen. These can then damage the baby in the womb in later pregnancies. Today, therefore, the Rh factor is routinely determined in pregnant women. Targeted antibody administration directly after birth helps to avoid complications. The antibodies bind the rhesus antigens of the child and make them harmless.

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Blood donation and blood transfusion

A blood donation can save the lives of patients. For a whole blood donation, about half a liter of blood is taken from the donor. This is then divided into its blood components. Because in a blood transfusion recipients rarely receive whole blood. Mostly targeted components of the blood of a donor are transmitted. In clinical practice, the red blood cells are particularly significant.

In addition to the whole blood donation, there is also the blood plasma donation. Here's the donor blood and separated immediately (during the donation) in a special device in plasma and blood cells. The blood cells are directed back into the body of the donor.

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