Final answer:
Hematopoiesis predominantly takes place in the red bone marrow, specifically in the spongy tissue of certain bones. While other organs can support blood cell production in specific conditions, red bone marrow is the major site post-birth. Granulocytes, a crucial type of white blood cell, are categorized as leukocytes.
Step-by-step explanation:
Hematopoiesis and Sites of Blood Cell Production
Hematopoiesis, or the process of blood cell production, primarily occurs in the red bone marrow. Although other organs such as the liver and spleen do take over hematopoiesis during the early stages of life and can serve as sites for extramedullary hematopoiesis in certain disease states, the bone marrow is the main site for this process post-birth. Specifically, red bone marrow within the spaces of spongy bone tissue is responsible for synthesizing red blood cells, white blood cells, and platelets. In adults, hematopoiesis is largely restricted to bones such as the cranial and pelvic bones, vertebrae, sternum, and the proximal epiphyses of the femur and humerus.
Granulocytes are a type of white blood cell, which classifies them as leukocytes (D). They are characterized by granules in their cytoplasm and play a critical role in the immune response.