What does the term 'diaphysis' refer to in bone anatomy?

The term 'diaphysis' refers specifically to the long, main portion of a long bone. This part is typically cylindrical in shape and extends between the two ends of the bone, known as the epiphyses. The diaphysis is primarily composed of compact bone, which provides strength and support for the bone structure during weight-bearing activities. This is crucial in understanding bone anatomy, as it helps differentiate between various parts of the bone, including the areas that are involved in growth and development versus those that are more focused on structural integrity.

In contrast, the end portions of bones are referred to as epiphyses. The outer layer of the bone is called the periosteum, while the soft tissue surrounding the bone mainly refers to the marrow or connective tissues that support the bone structure but are distinct from the diaphysis itself.