AEMCA Practice Exam

What does the diaphysis refer to in bone structure?

1. The end parts of the bone

2. The growth plate of the bone

3. The long shaft of the bone

4. The outer layer of the bone

The correct answer is: The long shaft of the bone

The diaphysis refers specifically to the long shaft of a bone. In skeletal anatomy, the diaphysis is the central part of a long bone, which is typically tubular in shape and provides structural support for the bone. This section is primarily composed of compact bone, which offers strength and rigidity while maintaining a relatively lightweight structure. The diaphysis is also involved in the production of blood cells, as the medullary cavity within houses bone marrow. In contrast, the end parts of the bone are known as the epiphyses, which serve different functions such as facilitating joint movement and providing surfaces for articulation. The growth plate, or epiphyseal plate, is the area of growing tissue near the end of the long bone and is crucial for bone lengthening during development, while the outer layer of the bone is referred to as the periosteum, which serves as a protective layer and supports muscle attachment. Understanding these terms helps clarify the organization of bone structure and the distinct functions of each part.