What is the hollow middle section of a long bone called?

The hollow middle section of a long bone is known as the diaphysis. This is the primary long shaft of the bone, which serves several important functions. The diaphysis is mostly composed of compact bone, providing strength and support while also housing the medullary cavity. The medullary cavity is lined with a thin layer of tissue known as endosteum and contains bone marrow, which is crucial for the production of blood cells.

In contrast, the epiphysis refers to the end parts of the long bone and is where the joint surfaces are located, typically covered with cartilage. The metaphysis is the region where the diaphysis meets the epiphysis, which is particularly important during the growth phase of the bone. The cortex, although also important, refers to the outer layer of the bone rather than a specific section like the diaphysis. Understanding these terms and their specific functions helps in studying the anatomy and physiological aspects of the skeletal system.