Biological Chemistry - Berezov, T. T., Korovkin, B. F. 1998

Blood

Blood is a fluid tissue responsible for transporting chemical substances (including oxygen) throughout the body, thereby integrating biochemical processes across various Cells and intercellular spaces into a unified system. In addition, blood performs protective, regulatory, thermoregulatory, and other vital Functions.

Blood consists of plasma and suspended formed elements. The latter include erythrocytes, leukocytes, and platelets. The normal blood volume averages 5200 mL in men and 3900 mL in women.

Plasma accounts for approximately 55% of total blood volume. Erythrocytes make up the bulk of the formed elements—44% of the total blood volume—while other cells account for only about 1%.

Under normal conditions, the relative density of whole blood is 1.050–1.064, plasma is 1.024–1.030, and cellular components are 1.080–1.097. Blood exhibits considerable viscosity due to its high protein and erythrocyte content. The viscosity of blood is 4 to 5 times greater than that of Water.

An important physicochemical indicator is the Osmotic Pressure of Blood Plasma. It is determined by the osmotic concentration, i.e., the total number of particles per unit volume. At a Temperature of 37°C, the osmotic pressure of blood plasma is approximately 7.6 atm. This value is primarily due to sodium chloride and other low-molecular-weight substances dissolved in the blood; about 0.03 atm is contributed by Proteins, mainly albumins, and is referred to as colloid-osmotic, or oncotic, pressure.

The close interconnection between blood and all body Tissues makes it possible to detect pathological Changes in the body through blood analysis, monitor the progression of pathological processes, and evaluate the efficacy of therapeutic measures.