![]() ![]() The cavity that extends the length of the diaphysis is the medullary cavity. Compact bone is very strong, and it provides the supportive strength of long bones. As the name implies, compact bone is formed of tightly packed bone that lacks the spaces found in spongy bone. In other epiphyses of the limbs, the spaces between trabeculae are filled with yellow bone marrow, which is composed of adipose tissue.Ĭompact bone forms the wall of the diaphysis and a thin superficial layer over the epiphyses. ![]() In an adult’s long bones, red bone marrow fills the spaces between trabeculae within the proximal epiphyses of the humerus and femur. Spongy bone reduces the weight of a bone without reducing its supportive strength. The trabeculae are covered by a thin connective tissue membrane called endosteum (en-dos ‘-te-um) that is involved in forming and repairing bone. It consists of thin rods or plates called trabeculae (trah-bek’-u-le) that form a meshlike framework containing numerous spaces. Spongy (trabecular) bone forms the internal structure of the epiphyses and the internal surface of the diaphysis wall. The internal structure of a long bone is revealed by a longitudinal section. ![]() Tiny blood vessels from the periosteum help to nourish the bone. The periosteum provides protection and also is involved in theįormation and repair of bone. Each epiphysis is joined to the diaphysis by an epiphysial (growth) plate of hyaline cartilage in immature bones or by an epiphysial line, a line of fusion, in mature bones.Įxcept for the region covered by articular cartilages, the entire bone is covered by the periosteum (per-e-os’-te-um), a dense irregular connective tissue membrane that is firmly attached to the underlying bone. The long shaft of bone that extends between the two epiphyses is the diaphysis (di-af’-e-sis). Its purpose is to protect and cushion the end of the bone, in addition to providing a smooth surface for movement of joints. ![]() The articular cartilage, which is composed of hyaline cartilage, covers the articular surface of each epiphysis. The epiphyses (plural) articulate with adjacent bones to form joints. Refer to as you study the following section.Īt each end of the bone, there is an enlarged portion called an epiphysis (e-pif’-e-sis). The femur, the bone of the thigh, will be used as an example in considering the structure of a long bone. ![]()
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