What is a Diaphysis?

Diaphyses (singular: diaphysis) refers to the shaft or body of a long bone, excluding the ends (called epiphyses). In other words, it is the midsection of a long bone that connects the two epiphyses. The diaphyses is made up of compact bone tissue and contains the bone's medullary cavity, which is filled with bone marrow.

In the context of skeletal anatomy, the diaphyses is important because it provides the main support for the bone's weight-bearing functions, while the epiphyses are responsible for the bone's movement and flexibility. The diaphyses also serves as a site for muscle attachment and provides a surface for the attachment of ligaments and tendons.

For example, in the femur (thigh bone), the diaphyses is the long shaft of the bone that connects the hip joint at one end to the knee joint at the other end. Similarly, in the humerus (upper arm bone), the diaphyses is the portion of the bone that connects the shoulder joint at one end to the elbow joint at the other end.