What is the periosteum? What is its function?

What is the periosteum? What is its function?

Its a dense fibrous membrane that covers the outer surfaces of modified rigid connective tissues i.e bones except for those that are capped by cartilage e.g joints.Periosteum is composed of two layers:
Fibrous periosteum(outer layer):
It is composed mostly of collagen. The bb(color(violet(fibroblast cells) in this layer are densely packed.
It contains lymphatic & blood vessels. It contain nerve fibres that induce pain in case of tissue damage.

This layer of periosteum serve as a site for muscular attachmnets to the bones.
It also allow different lymphatic and blood vessels to penetrate into bones. These help the bones to get nutrients and also supply the bones with osteocytes, thorugh Volkmans canals.

Cambium or osteogenic periosteum(inner layer):
It contains osteogenic or progenitor cells which later develop into osteoblasts. It is not as tightly packed.

The osteoblasts(evolved from progenitor cells) play salient role in in the growth and repair of bony tissue.

Most growth in bones is produced by osteoblasts. Osteoblasts produce hard mineral matrix by absorbing Ca^(2+) ions in the blood. In case of fracture or are damage to bones, the osteoblasts of the periosteum repair the damage and replace the mineral matrix, often reinforcing the bone beyond its original thickness.

Hope it helps…