What is the name of the middle section of a long bone that makes up most of its length?

The middle section of a long bone, which constitutes the majority of its length, is referred to as the diaphysis. This central part of the bone serves several vital functions. It contains the medullary cavity, which is filled with bone marrow, a key player in the production of blood cells. The diaphysis is also primarily composed of a dense and compact form of bone tissue that provides strength and structural support, enabling the bone to withstand the forces placed upon it during movement and weight-bearing activities.

In contrast, the epiphysis refers to the rounded ends of the bone, which articulate with adjacent bones at the joints. The metaphysis is the region where the diaphysis meets the epiphysis and is involved in the growth of bone during development. The articular surface is the specific part of the epiphysis that forms a joint with another bone, covered by smooth cartilage to facilitate movement. Each of these sections plays distinct roles in the overall anatomy and function of long bones, but it is the diaphysis that primarily comprises the length of the bone.