Diaphysär

Diaphysär, or diaphyseal, describes anything relating to the diaphysis, the central shaft of a long bone that lies between the proximal and distal ends, the epiphyses. The diaphysis provides structural support and acts as a lever for movement.

Anatomically, the diaphysis is composed mainly of dense cortical (compact) bone arranged in a cylindrical shell around a medullary cavity. The outer surface is covered by the periosteum, a vascularized connective tissue, while the inner surface is lined by the endosteum. The medullary cavity houses bone marrow and is lined by a thin endosteal layer. In adults, the cavity often contains yellow marrow, whereas red marrow is more common near the ends of long bones and in other marrow-rich sites.

Development and growth involve endochondral ossification of the diaphysis during fetal development. Longitudinal growth occurs at the epiphyseal plates (growth plates) near the ends of the bone; these plates gradually close during adolescence, after which the diaphysis can no longer lengthen.

Blood supply to the diaphysis comes mainly from the nutrient artery, which enters through a nutrient foramen to supply the inner cortical bone and marrow. Periosteal arteries nourish the outer cortex, and metaphyseal vessels support the ends of the bone.

Clinical relevance includes diaphyseal fractures, which affect the shaft of long bones and require management such as immobilization or intramedullary nailing. Healing depends on intact blood supply and stable alignment. The term diaphysär is used in German to denote characteristics of the diaphysis, with diaphyseal used in English.