How much blood does the human body contain?

When the human body suffers trauma, a large amount of blood will flow out of the wound. If the situation is not serious, the coagulation function of platelets will stop the bleeding quickly and avoid excessive blood loss. However, in some serious accidental situations, such as car accidents, fractures, falls, etc., the amount of blood outflow from the wound will be very high, and blood transfusions will be needed in the process of treating the injured. So, how much blood does the human body contain?

How many milliliters of blood are there in the human body?

Under normal circumstances, the total blood volume in a person's body is about 8% of body weight. If the body weight is 100 catties, the blood volume is 8 catties. That is 4 kilograms. The total volume is 4000 ml, of which plasma accounts for more than half.

The blood volume of a healthy person is not fixed. It varies between different individuals and also changes under different conditions of the same individual. Generally speaking, men have more blood than women; obese people have more fat, so the amount of blood per kilogram of body weight is less than normal.

Blood cells are divided into three categories: red blood cells, white blood cells, and platelets.

Blood component analysis

Blood is composed of plasma and blood cells.

1. Plasma

Plasma is equivalent to the intercellular matrix of connective tissue, while serum is a light yellow translucent liquid, which contains, in addition to a large amount of water, inorganic salts, fibrinogen, albumin, globulin, enzymes, hormones, various nutrients, metabolites, etc. These substances have no definite form, but have important physiological functions.

1L of plasma contains 900-910g of water (90%-91%). 65-85g protein (6.5%-8.5%) and 20g low molecular weight substances (2%). Low molecular weight substances include a variety of electrolytes and small molecular organic compounds, such as metabolites and certain other hormones. The electrolyte content in plasma is basically the same as that in tissue fluid.

(ii) Blood cells

During the life of the body, blood cells are constantly metabolized. The average life span of red blood cells is about 120 days, while the survival period of granulocytes and platelets generally does not exceed 10 days. The life span of lymphocytes varies from a few hours to several years.

The production of blood cells and platelets comes from the hematopoietic organs. Red blood cells, granulocytes and platelets are produced by the red bone marrow, while agranulocytes are produced by the lymph nodes and spleen.

Blood cells are divided into three categories: red blood cells, white blood cells, and platelets.