What is the name of the membrane covering the outside of the diaphysis?

The membrane covering the outside of the diaphysis is known as the periosteum. This dense layer of vascular connective tissue provides a protective layer for the bone and serves multiple functions. It contains blood vessels and nerves that are essential for bone health, growth, and repair, contributing to the nourishment of the bone tissue. Additionally, the periosteum is instrumental in the attachment of tendons and ligaments, thus playing a critical role in the overall biomechanics and function of the skeletal system.

The endosteum, although associated with bone structure, lines the inner surfaces of the bone, such as the medullary cavity, rather than covering the diaphysis. The metaphysis refers to the region between the diaphysis and the epiphysis, playing a role in the growth of long bones but does not cover the bone. Articular cartilage is the smooth tissue that covers the ends of bones in joints, enabling smooth movement and reducing friction, which is entirely different from the function of the periosteum.