Which component makes up about 55% of blood by volume?

Which component makes up about 55% of blood by volume?

• A. 40-45% erythrocytes
• B. <1% leukocytes
• C. <1% platelets
• D. 55% plasma

Answer: (D)

Plasma is the liquid component of blood that makes up about 55% of its volume. It functions as the fluid matrix that carries water, electrolytes, nutrients, hormones, waste products, and most plasma proteins (like albumin, globulins, and fibrinogen). This fluid layer helps maintain blood volume and pressure and serves as the medium for transporting substances around the body. The remaining ~45% consists of formed elements: erythrocytes (red blood cells) make up about 40–45% of blood volume, while white blood cells and platelets together account for less than 1%. So, the component that fits the 55% figure is plasma.

Plasma is the liquid component of blood that makes up about 55% of its volume. It functions as the fluid matrix that carries water, electrolytes, nutrients, hormones, waste products, and most plasma proteins (like albumin, globulins, and fibrinogen). This fluid layer helps maintain blood volume and pressure and serves as the medium for transporting substances around the body.

The remaining ~45% consists of formed elements: erythrocytes (red blood cells) make up about 40–45% of blood volume, while white blood cells and platelets together account for less than 1%. So, the component that fits the 55% figure is plasma.