Periosten

Periosten is a term that refers to the dense, fibrous connective tissue that surrounds bones. It is a critical component of the skeletal system, playing vital roles in bone growth, repair, and protection. The periosten is composed of two layers: an outer fibrous layer and an inner cellular layer. The outer layer provides structural support and anchors the muscles and tendons to the bone. The inner cellular layer contains osteoblasts, which are cells responsible for bone formation, and osteoclasts, which are cells involved in bone resorption. This dynamic cellular activity allows the periosten to adapt to mechanical stress and facilitates bone remodeling throughout life.

During bone development, the periosten is essential for the appositional growth of long bones, meaning growth in width. It also plays a crucial role in fracture healing. When a bone breaks, the periosten initiates a cascade of events that lead to the formation of a callus, a temporary structure that bridges the fracture gap and stabilizes the broken bone. This callus is eventually remodeled into new bone tissue, restoring the bone's original strength and integrity. Furthermore, the periosten is richly supplied with blood vessels and nerves, which contribute to bone nutrition and sensation. Damage to the periosten, such as in periostitis, can lead to significant pain and inflammation.