In the context of bone marrow anatomy and function, where are red blood cells (erythrocytes) primarily produced in adults?

• A. Red bone marrow (hematopoietic marrow) within spongy bone
• B. The periosteum covering the outer surface of bones
• C. Yellow bone marrow within the medullary cavity of long bones
• D. Compact (cortical) bone of the diaphysis

Answer: (A)

Verified step by step guidance

1. Understand the function of red bone marrow: It is the primary site of hematopoiesis, the process of producing red blood cells (erythrocytes), white blood cells, and platelets.
2. Identify the location of red bone marrow in adults: Red bone marrow is found mainly within the spongy (cancellous) bone, especially in flat bones like the pelvis, sternum, and ribs, as well as the epiphyses of long bones.
3. Differentiate red bone marrow from yellow bone marrow: Yellow bone marrow primarily stores fat and is found in the medullary cavity of long bones; it does not actively produce blood cells under normal conditions.
4. Recognize that the periosteum is a dense connective tissue layer covering the outer surface of bones and does not participate in blood cell production.
5. Note that compact (cortical) bone forms the dense outer layer of bone and provides structural support but does not contain marrow spaces for hematopoiesis.