Blood formation occurs primarily in which part of the skeletal system?

Blood formation, or hematopoiesis, occurs primarily in the bone marrow, which is a spongy tissue found in the interior of certain bones. The bone marrow is where stem cells are located, which can develop into all the different types of blood cells, including red blood cells, white blood cells, and platelets.

While bones provide the structure and protection necessary for the body, and cartilage serves as a flexible support in various joints, these options do not directly participate in the process of blood cell production. Ligaments, which connect bones to other bones, also do not have a role in forming blood. Therefore, the bone marrow is the correct choice, as it is specifically designed for the production of blood cells within the skeletal system.