What is the name of the shaft or middle section of a long bone?

The shaft or middle section of a long bone is called the diaphysis. The diaphysis is the long, tubular portion of the bone, which is primarily made of compact bone and provides strength and support for the bone structure. It contains the medullary cavity, which is important for the production of blood cells and storage of fat.

In long bones, the diaphysis connects the two ends, known as the epiphyses, which are often involved in joint articulation and are covered by cartilage. The metaphysis is the region where the diaphysis meets the epiphysis and is where growth occurs in the bone during development. Cartilage is a flexible connective tissue found in various parts of the body, but it is not the name of the shaft itself. Thus, diaphysis is the correct term to identify the central part of a long bone.