Which of the following composes the greatest amount of volume in blood?
a. erythrocytes
b. leukocytes
c. white blood cells
d. platelets
Answer: a. erythrocytes
Erythrocytes, or red blood cells, compose the greatest volume of blood, accounting for approximately 99% of the cells. A hematocrit is a measurement of the actual percentage of the blood's volume, which consists of red blood cells. People with lower hematocrit levels (women, typically) have reduced hemoglobin content.