Sites of hematopoiesis include all but a. red marrow of spongy bone b. the heads of femur and humerus in adults c. medullary cavities in bones of infants d. medullary cavities in bones of a healthy adult.

Verified step by step guidance

1. Understand that hematopoiesis is the process of blood cell formation.
2. Recognize that in adults, hematopoiesis primarily occurs in the red marrow of spongy bone, particularly in flat bones and the heads of long bones like the femur and humerus.
3. Note that in infants, hematopoiesis occurs in the medullary cavities of bones, as they have more red marrow compared to adults.
4. Identify that in healthy adults, the medullary cavities of long bones are typically filled with yellow marrow, which is not active in hematopoiesis.
5. Determine which option does not fit the typical sites of hematopoiesis by considering the role of red and yellow marrow in different life stages.

Key Concepts

Hematopoiesis

Hematopoiesis is the process of blood cell formation, which occurs primarily in the bone marrow. In adults, this process mainly takes place in the red marrow of certain bones, while in infants, it can occur in the medullary cavities of various bones. Understanding where hematopoiesis occurs is crucial for identifying the correct answer to the question.

Bone Marrow Types

Bone marrow is classified into two types: red marrow, which is involved in hematopoiesis, and yellow marrow, which primarily stores fat. In adults, red marrow is found in specific locations, such as the pelvis and the proximal ends of long bones, while yellow marrow replaces red marrow in other areas. This distinction is important for determining the sites of hematopoiesis mentioned in the question.

Medullary Cavity

The medullary cavity is the central cavity of bone shafts where yellow marrow is stored in adults, and red marrow is found in infants. In adults, the medullary cavities of long bones typically do not participate in hematopoiesis, as red marrow is largely replaced by yellow marrow. Recognizing the role of the medullary cavity in different age groups is essential for answering the question accurately.