Definition (Periostem): This is the fibro-vasculo-cellular layer covering the external surface of bone, expect the articular surface.
The outer surface of bone, other than the articular surface is covered by a fibro-vascular layer called periosteum.
Structure: It consists of two layers:
- Outer fibrous layer: It consists of dens fibrous connective tissue and contains a network of blood vessels.
- Inner osteogenic layer: It is composed of more loosely arranged connective tissue, some collagenous fibers and connective tissue cells.
- Periosteum provides medium through which muscles, tendons & ligaments are attached to bone.
- As it is more vascular, it forms avascular bed from which it sends capillaries to nourish the underlying bone.
- The periosteum helps in bone forming during the growth period and during repair of fracture.
- It prevents overgrowth of bone.
- Fibrous layer acts as a limiting membrane, which keeps the osteogenic layer in the proper position.