Percentage of plasma in blood :

Question

Accepted Answer

The correct option is (1):
The normal and most commonly accepted percentage of plasma within the total volume of human blood ranges from approximately 50% to 60%. Plasma is the pale, yellowish liquid component that makes up the extracellular matrix of blood, with the remaining volume consisting of formed elements (erythrocytes, leukocytes, and thrombocytes). Specifically, plasma typically accounts for about 55% of the blood's volume, which places the 50%-60% range as the correct physiological measurement. This liquid matrix is essential as it carries blood cells, nutrients, hormones, antibodies, and waste products throughout the body, making it a vital component for systemic function and homeostasis.

The incorrect option is (2):
A range of 70%-80% plasma is physiologically inaccurate and would indicate a massive decrease in the number of blood cells, particularly red blood cells. Since the formed elements normally constitute about 45% of the total blood volume, a plasma percentage this high would mean the cellular component is critically low (20-30%). This abnormal ratio would be indicative of a pathological condition like severe anemia or hemodilution, where the oxygen-carrying capacity of the blood would be drastically reduced.

The incorrect option is (3):
A plasma percentage of 30%-40% is significantly lower than the normal physiological range. This measurement would imply that the formed elements constitute a dangerously high proportion of the blood, roughly 60%-70%. This condition, known as polycythemia or hemoconcentration, causes the blood to become excessively thick or viscous. Highly viscous blood flows poorly, which drastically increases the workload on the heart and raises the risk of severe cardiovascular events like clotting, strokes, or heart attacks.

The incorrect option is (4):
The range of 80%-90% is extremely inaccurate for the percentage of plasma in whole blood. Although plasma itself is composed of over 90% water, its volume relative to the total blood volume never reaches this high under normal or even moderate pathological conditions. Such a high plasma percentage suggests an extreme level of hemodilution, practically devoid of formed elements, which is incompatible with life as it would result in immediate and complete failure of oxygen transport and immune function.