What fibrous is covering the surface of bone that involved in thickening bone?

The periosteum is a fibrous membrane that covers the surface of all bones except for the joints. It envelops the bone and consists of two layers: the outer fibrous layer and the inner cellular layer. The fibrous layer is composed of dense connective tissue and functions to protect the bone and attach tendons, ligaments, and muscles. The cellular layer consists of osteoprogenitor cells, which are responsible for bone growth and repair.