What does the blood tissue connect to

The blood, the most important transport system in our body

The blood fulfills a variety of tasks in our body. It transports oxygen from the lungs to the various organs and brings nutrients, waste materials and hormones to their destinations. The defense against pathogens by our immune system also takes place for the most part in the blood. In addition, in the event of an injury, the blood ensures that the wound is closed quickly.

About 5–6 liters of blood flow in an adult human body. It is transported in a system of blood vessels that is around 96,000 km long - that's more than twice the circumference of the earth!

The blood vessels branch out into ever finer veins on their way from the heart to the organs. In this way they can reach every tissue in the body. Only our hair, toenails and fingernails, the cornea of ​​the eyes and the tooth enamel are not supplied with blood.

An extensive transport system

The blood ensures that all cells in the body have enough “fuel” to generate energy: It brings them oxygen and energy-rich substances such as glucose. The carbon dioxide that is produced during combustion is transported away again and exhaled through the lungs. The blood also distributes mineral salts and vitamins in the body and carries waste and toxins to the excretory organs, especially the liver and kidneys.

Defense against pathogens

Pathogens such as viruses, bacteria or parasites also use the blood to spread and multiply in the body. If they manage to overcome the barrier of the skin or mucous membranes and enter the body, an infection can occur. Therefore, they must be combated as soon as possible.

For this purpose, the cells of the immune system circulate in our blood. The white blood cells represent the "police" of our body. This police includes the Granulocytes and Macrophagesthat trigger a general defense reaction. They are also called phagocytes because they recognize intruders in the blood and tissue, absorb them and destroy them. This process is called phagocytosis.

Other cells of the blood police, the different types of Lymphocytes, set specific defense reactions in motion. Helper cells remember the structure on the surface of the pathogen and pass this information on to other cells. Plasma cells then begin to produce targeted weapons against the intruder: the antibodies. Killer cells destroy body cells that have already been attacked by a pathogen so that it cannot multiply there. And Memory cells ultimately ensure that the body remembers an infection for a long time and that the immune reaction happens much faster the next time. Thanks to them, you become immune to certain diseases, so you only go through them once in a lifetime.

Close wounds and avoid blood loss

Of course, it is even better if pathogens cannot even penetrate the bloodstream. Therefore, when injured, the body tries to close the wound as quickly as possible. The blood coagulates and forms a crust that only falls off when the blood vessel and the skin over it have healed again. Another type of blood cell, called platelets, is involved in blood clotting. In addition, various coagulation factors are required, these are proteins in the blood fluid (also called blood plasma).

Heavily bleeding wounds must also be bandaged, as blood loss of more than two liters can be fatal. Such injuries often require a blood transfusion afterwards. There are also diseases in which blood clotting is impaired; in such cases, additional coagulation factors must be given, for example through a transfusion of blood plasma.

Editors SimplyScience.ch
Blood donation from the Swiss Red Cross (www.das-blut.ch), kiknet.ch/kik AG