Where are red blood cells produced in the body?

• A. Bone marrow
• B. Brain
• C. Spleen
• D. Lymph nodes

Answer: (A)

Red blood cells are produced in bone marrow. In adults, stem cells in the red bone marrow divide and differentiate through several stages into mature erythrocytes, in a process called erythropoiesis. Erythropoietin from the kidneys signals the marrow to make more red blood cells when oxygen levels are low, helping maintain the right number of RBCs in the blood. The brain doesn’t generate blood cells; its role is control and coordination. The spleen helps filter and recycle old red blood cells and, under certain conditions, can contribute to blood cell production, but it is not the normal site of production. Lymph nodes are part of the immune system and do not produce red blood cells.