Erythrocytes are which type of blood cell?

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

Answer: (A)

Erythrocytes are the cells whose main job is oxygen transport in the blood, and the term literally means red cell. That’s why the best match is red blood cells. Their hemoglobin carries oxygen from the lungs to tissues and returns carbon dioxide for disposal. They’re the most abundant blood cells and have a distinctive biconcave shape that increases surface area for gas exchange and makes them flexible as they flow through tiny vessels. In mammals they lack a nucleus when mature, maximizing space for hemoglobin. They’re produced in the bone marrow through erythropoiesis, regulated by erythropoietin, and typically survive about 120 days. This set apart white blood cells, which defend against infection; platelets, which help with clotting; and plasma, the liquid portion of blood.