What term describes the shaft or the long tubular portion of long bones?

The term that describes the shaft or the long tubular portion of long bones is diaphysis. The diaphysis is the main or central part of a long bone, which provides structural support and strength. It is primarily made of compact bone that is organized to resist bending and torsional forces. This area of the bone contains the medullary cavity, where bone marrow is found, playing an important role in hematopoiesis (the production of blood cells) and fat storage.

In contrast, the epiphysis refers to the ends of the long bones, which are involved in forming joints and articulations. The metaphysis is the region where the diaphysis meets the epiphysis and is primarily active during the growth phase of the bone. Articular cartilage covers the surfaces of the epiphysis at the joint interfaces, aiding in smooth movement and shock absorption. Understanding these distinctions helps in grasping the structure and functioning of long bones in the skeletal system.