What significant substance does spongy bone contain?

Spongy bone, also known as trabecular or cancellous bone, is primarily known for housing red bone marrow. The presence of red bone marrow in spongy bone is crucial because this is where hematopoiesis, the process of blood cell production, takes place. Red bone marrow is essential for producing red blood cells, white blood cells, and platelets, thus playing a vital role in the body's immune response and oxygen transport.

While spongy bone does contain minerals, which contribute to its structural integrity and strength, the key characteristic that distinguishes it in terms of function is its production of blood cells. Similarly, it does have collagen fibers, which are significant components throughout bone tissue, providing flexibility and tensile strength, but they are not unique or specific to spongy bone alone. Yellow bone marrow, which is mainly involved in fat storage, is primarily found in the central cavities of long bones rather than in spongy bone, further emphasizing the distinct role of red bone marrow in spongy bone.