Blood, tissue fluid and lymph - the internal environment of the body in which the vital activity of cells, tissues, organs. The internal environment of a person ensures the efficiency of all organs, tissues of the human body. Blood circulating throughout the body delivers nutrients, oxygen, hormones and various types of enzymes to the tissues, taking the decay products and delivering them to the organs of excretion. In order for this system to work normally, the volume of circulating blood is determined in each organism. For each person, he is individual.
The concept
It is difficult to establish the exact volume of circulating blood in a person, since this is a dynamic phenomenon that varies widely. When a person is at rest, only part of the blood takes part in the circulation, and only the amount necessary to complete the cycle in a short period of time. On the basis of this process, the concept of “circulating blood volume” appeared in medicine.
What determines the volume
In the human body, the volume of circulating blood will always have different indicators. This is due to physique, living conditions, physical activity, general condition, age, gender. So, in the same person at rest and during physical activity, volume indicators will be different. In the first case, they will decrease by about 10-15% of the initial data.
Normally, with an average degree of physical activity, the volume of circulating blood is 50-80 ml per kilogram of weight. You can consider this with examples. So, for men weighing 70 kilograms, the volume of circulating blood is 5.5 liters, which is about 80 ml / kg of weight. A woman is slightly less - about 70 ml / kg of weight.
In a healthy person who is in a supine position for more than seven days, the volume decreases by ten percent.
What volume consists of
It is believed that in the body of an adult male about 5.5 liters of blood. Of these, 3-3.5 liters is plasma, and the rest is red blood cells.
About 90,000 liters of blood pass through the vessels throughout the day. About 20 liters of this amount from the smallest blood vessels in the tissue as a result of filtration pass.
"Parts" of blood
The total volume of human circulating blood is conventionally divided into actively moving along the vascular bed and deposited, i.e. the part that does not take part in the blood circulation. If necessary, it is quickly included in the process, but for this special hemodynamic conditions must be created.
It is generally accepted that the volume of deposited blood is twice the amount of actively circulating. The deposit is in a state of incomplete stagnation: some of it is periodically included in the moving, and from there, the same amount of circulating goes into the state of deposit.
The volume of circulating blood is changed by compensating for the capacity of the venous bed.
Factors Affecting BCC
The main factors that affect the blood volume in the human body are:
- normalization of fluid volume between the interstitial space and blood plasma;
- red blood cell normalization;
- normalization of fluid exchange between the environment and plasma.
The processes of regulating the amount of blood are regulated by various organs, systems: kidneys, sweat glands, etc.
Volume regulation
Blood volume is regulated by the nervous system with the help of atrial receptors A, which respond to pressure changes, and type B, that respond to atrial distension and are sensitive to changes in the amount of blood.
Infusion of various solutions has an effect on volume. When infusing a solution of sodium chloride into a vein, the blood volume does not increase for a long time. In this case, excess fluid is excreted from the body using enhanced diuresis.
With dehydration, deficiency of salts, the injected solution helps to restore disturbed balance.
With the introduction of glucose, dextrose into the blood, fluid is transported into the interstitial, and then into the cell space. If the dextrates are injected for a long period, they can contribute to an increase in the volume of circulating blood.
Blood distribution
The distribution of the amount of blood in the body occurs as a percentage and is as follows:
- the share of the pulmonary circulation is about 25%;
- heart - 10%;
- lungs - 12%.
The remaining volume is accounted for by a large circle of blood circulation, that is, about 75%. Of these, 20% circulate in the arterial system. About 70% of the bcc is located in the venous system. The capillary bed accounts for about 6%.
With blood loss, the volume of blood decreases - plasma and red blood cells; with dehydration, water is lost, and with anemia - only the number of red blood cells. With these types of pathological processes, it is urgent to conduct treatment in the form of replenishing the blood volume. During blood loss, a transfusion is carried out, with dehydration, substances are introduced that contribute to the normalization of the water balance.