Which of these components makes up the greatest portion of whole blood by volume?

• A. Platelets
• B. Plasma
• C. White blood cells
• D. Red blood cells

Answer: (B)

Verified step by step guidance

1. Begin by understanding the composition of whole blood. Whole blood consists of plasma, red blood cells, white blood cells, and platelets.
2. Plasma is the liquid portion of blood and serves as a transport medium for nutrients, hormones, and waste products. It makes up about 55% of the total blood volume.
3. Red blood cells, also known as erythrocytes, are responsible for carrying oxygen from the lungs to the rest of the body and returning carbon dioxide to the lungs for exhalation. They make up about 45% of the blood volume.
4. White blood cells, or leukocytes, are part of the immune system and help fight infections. They make up less than 1% of the blood volume.
5. Platelets, or thrombocytes, are involved in blood clotting and also make up less than 1% of the blood volume. Therefore, plasma constitutes the greatest portion of whole blood by volume.