Bone is the main

BONE

Bone is the main component of the skeleton in the adult human. Like cartilage, bone is a specialized form of dense connective tissue. Bone gives the skeleton the necessary rigidity to function as attachment and lever for muscles and supports the body against gravity.

Two types of bone can be distinguished macroscopically:

Trabecular bone (also called cancellous or spongy bone) consists of delicate bars and sheets of bone, trabeculae, which branch and intersect to form a sponge like network. The ends of long bones (or epiphyses) consist mainly of trabecular bone. Compact bone does not have any spaces or hollows in the bone matrix that are visible to the eye. Compact bone forms the thick-walled tube of the shaft (or diaphysis) of long bones, which surrounds the marrow cavity (or medullary cavity). A thin layer of compact bone also covers the epiphyses of long bones.

Bone is, again like cartilage, surrounded by a layer of dense connective tissue, the periosteum. A thin layer of cell-rich connective tissue, the endosteum, lines the surface of the bone facing the marrow cavity. Both the periosteum and the endosteum possess osteogenic potency. Following injury, cells in these layers may differentiate into osteoblasts (bone forming cells) which become involved in the repair of damage to the bone.