What is the central cavity in the shaft of a long bone called?

The central cavity in the shaft of a long bone is called the medullary canal. This hollow region within the diaphysis, or shaft, of the bone plays a critical role in the storage of bone marrow, which can be either red or yellow. Red marrow is involved in the production of blood cells, while yellow marrow primarily consists of adipose tissue and serves as an energy reserve. The medullary canal is lined by the endosteum, a thin layer of connective tissue that helps in the growth and repair of the bone. This specific anatomical feature is essential to the overall function of long bones in the skeletal system, allowing for both structural support and effective hematopoiesis. Other terms such as epiphyseal line, periosteum, and endosteum relate to different structures surrounding or lining the bone but do not denote the central cavity itself.