What is the rounded end of a long bone that contains the joint structure?

The rounded end of a long bone that contains the joint structure is known as the epiphysis. This region is specifically designed to articulate with other bones, forming joints. The structure of the epiphysis includes a layer of cartilage known as articular cartilage, which smooths out the surfaces for joint movement and helps reduce friction between bones during movement.

The epiphysis also houses spongy bone, which is lighter and contains red bone marrow, responsible for blood cell production. The overall design of the epiphysis enables it to distribute loads and withstand the stresses placed on joints during activities such as walking or running.

In contrast, the diaphysis refers to the long, tubular shaft of the bone, primarily composed of dense, compact bone and provides strength and support. The marrow cavity is the internal space within the diaphysis that contains bone marrow, while the periosteum is a membrane that covers the outer surface of the bone, playing a role in growth and repair, as well as providing a site for muscle attachment.