Blood plasma
As already mentioned, blood plasma makes up about 55% of the total blood volume. The blood plasma is blood without cells. Blood plasma consists of approximately 90% water and 10% solid components such as protein, electrolytes and carbohydrates.
Plasma proteins One litre of blood contains approx. 60 – 80 g of protein. Due to its size it cannot penetrate the plasma wall and exerts a water-attracting force (colloid-osmotic pressure).
Thus, by suction, the water from the interstitial space returns to the capillary. The level of the colloid-osmotic pressure (normal value approx. 25mmHg) does not determine the size of the protein molecules, but their number.
The small-molecular albumins are involved in 75% of the colloid-osmotic pressure. Consequently, an albumin decrease increases the extravasal and decreases the intravasal fluid volume and thus leads to edema. In addition, albumins assume a transport function for ions and exogenous substances such as antibiotics.
Globulins are larger molecules that perform a transport function. In addition, globulins contain immunoglobulins which have a defence function against bacterial foreign substances. Their proportion is about 32g per litre of blood plasma.
The fibrinogen is important for blood coagulation and is represented with approx. 3g per litre of blood. In addition to the water-binding function, defence function and transport function, the protein contained in the blood is important as an amino acid reservoir. The amount of electrolytes in the blood is about 9g/litre and is mainly determined by Na+ and Cl-. Other components of blood plasma: In addition to proteins, glucose, free fatty acids, cholesterol, enzymes and hormones are contained in the blood, but only in very small quantities.
Blood defence system
If foreign substances such as bacteria enter the bloodstream, either an unspecific defence function is created by macrophages or a specific defence action of the so-called immune reaction takes place. The human immune system has more than 1 billion lymphocytes for this specific defence function. The lymphocytes are produced in the lymph nodes, spleen and bone marrow and are transported into the bloodstream.
The antibodies of the human body amount to about 100 million trillion. The lymphocytes are differentiated into T-form for specific cellular defence and B-form for specific humoral defence. The B-lymphocytes are responsible for the formation of large quantities of antibodies.
They are imprinted in the lymph nodes and tonsils for their specific task and released into the blood and lymphatic system. On contact with the antigen, the B-lymphocytes transform into plasma cells and produce antibodies. The T-lymphocytes take over the function if not all pathogens have been killed by the non-specific defence or specific humoral defence.
The T-lymphocytes are imprinted in the thymus for their respective task. The T-lymphocytes dock with the antigen with their specific receptor. The T lymphocytes are responsible for the killing of cancer cells and transplanted tissue.
Another form of lymphocytes are the null cells, which make up about 10% of all lymphocytes and take over unspecific “killer functions”. Active immunization Active immunization is used to prevent life-threatening infections. In this process, the body is administered weakened but still living pathogens, which trigger the formation of antibodies.
For example, protective vaccination against swine flu, measles, diphtheria. Passive immunisation Passive immunisation involves the administration of antibodies which have been formed in the organism against the specific antigen. Compared to active immunisation, the result is an immediate effect.
