Which structure is primarily responsible for providing support and nutrition to bone cells?

The periosteum is a crucial structure that covers the outer surface of bones, serving as a protective layer and playing a significant role in nourishment and support for bone cells. This dense layer of connective tissue is rich in blood vessels and nerves, which supply essential nutrients to the bone and facilitate the healing process. The periosteum's vascular network aids in the delivery of oxygen and nutrients, which are vital for maintaining healthy bone tissue and supporting the metabolic activities of bone cells, particularly osteoblasts and osteocytes.

While bone marrow is important for producing blood cells, it does not primarily provide support or nutrition to bone cells. Cancellous bone, also known as trabecular bone, has a spongy structure that contributes to the overall strength and weight reduction of bones but is not the primary nourishing structure. Osteoid is the unmineralized organic component of the bone matrix, necessary for bone formation but not directly responsible for the nourishment of bone cells in the same way that the periosteum is. Thus, the periosteum stands out as the correct answer due to its specific functions related to nutrition and support for bone cells.