BIOCHEMISTRY - Key Regulators and Biological Fluids of the Human Body - 2016

5. BLOOD BIOCHEMISTRY

5.2. Physicochemical Properties of Blood

Blood volume. The Human Body contains about 5.5 liters of blood, which accounts for approximately 1/13 of total body weight.

Blood density. Ranges from 1.05 to 1.06 g/cm³.

Viscosity. High; it can vary depending on Water and protein content.

Osmotic pressure. At a Temperature of 37 °C, it is 7.7 - 8.1 atm. When hypotonic solutions or water are introduced into the bloodstream, the pressure decreases and erythrocytes are destroyed (hemolysis), whereas administration of hypertonic solutions increases the pressure, drawing water out of erythrocytes and causing them to shrink. This pressure is maintained at a constant level by the Kidneys.

Active reaction (pH). pH = 7.4. This value is maintained by the buffer capacity—the Blood Buffer Systems, which include bicarbonates (53%), phosphates (5%), Plasma Proteins (7%), and erythrocyte Hemoglobin (35%).

Alkaline reserve of blood. Determined by The amount of alkaline substances that neutralize acids entering the bloodstream. The alkaline reserve is expressed in milliliters of CO₂ bound by 100 ml of blood. In an adult, the alkaline reserve is 50 - 70 ml of CO₂, whereas in athletes it is 10 - 15% higher.

During intense muscular activity, large amounts of acidic substances enter the bloodstream, resulting in a decreased blood buffer capacity (leading to acidosis). When ascending to altitudes of 3,000 meters or higher, blood alkalinity increases due to the loss of acidic substances (leading to alkalosis). Acidosis and alkalosis can be compensated (if the pH level remains unchanged) or uncompensated. Significant shifts in pH indicate Metabolic Disorders and impaired physiological Functions, which can be life-threatening.