Coverings of bone

The two coverings of bone are periosteum and endosteum.

Periosteum

Periosteum is the membrane, which invests the outer surface of the bone except its articular areas where it is covered by articular cartilage.

The outer layer of bones is protected by the periosteum, it is a dense fibrous membrane. A fibrous outer layer and a cellular inner layer make up its two layers. In contrast to the cellular layer, which is made up of fibroblasts, osteoblasts, and osteoclasts, the fibrous layer is made up of collagen fibres. In veterinary anatomy, the periosteum fulfils a number of vital roles. It serves as an attachment point for ligaments and tendons as well as protection for the underlying bone, bone growth, and bone repair. The bone is additionally innervated and supplied with nutrients by the blood vessels and nerves that are found there.

The periosteum consists of an outer protective fibrous layer and an inner cellular osteogenic layer.

Endosteum

Endosteum is a thin membrane lining the medullary cavity (contains bone marrow) and larger Haversian canals. It is also called as medullary membrane.

A delicate, thin membrane called the endosteum covers the inside of bones. Mostly osteoprogenitor cells and osteoblasts make up its single layer of cells. The remodelling and expansion of bone tissue depend heavily on the endosteum. It contributes to the formation of new bone by giving osteoblasts a surface on which to work and deposit new bone matrix. Osteoclasts, specialised cells in charge of bone resorption, are also present. Additionally, the endosteum participates in the transfer of nutrients and minerals from the bone to the bone marrow cavity, which helps to maintain the overall homeostasis of the skeletal system.