Anatomy of a Long Bone
Each end of the long bone is called the epiphysis. You may refer to either the proximal epiphysis or the distal epiphysis. It is composed of mostly spongy bone enclosed by a thin layer of compact bone. The epiphyseal plate is a flat plate of hyaline cartilage seen in young, growing bone. This is the site of bone growth. The remaining epiphyseal line can still be seen in adults once growth has stopped.
The epiphysis is covered with articular cartilage. It is made of hyaline cartilage. The purpose of this is to decrease friction at joint surfaces.
The long shaft of the bone is called the diaphysis. It makes up most of the bone's length. It is composed of compact bone.
The outside of the diaphysis is covered by the periosteum. It is a fibrous connective tissue membrane. There are specialized perforating fibers that secure the periosteum to the underlying bone.
The endosteum is a thin layer of connective tissue lines the inside of the bony tissue, creating the medullary cavity.
The hollow inside of the bone is referred to as the medullary cavity. Red (site of hematopoiesis) and yellow (mostly fat) bone marrow are stored here. In adults, red bone marrow is in cavities of spongy bone and epiphysis of some long bones.