Periosteum is a thin layer of connective tissue that surrounds and covers the surface of bones in the human body. It plays a crucial role in the growth and repair of bone tissue, as well as providing support and protection for the underlying bone.
Structure
The periosteum is composed of two layers: an outer fibrous layer and an inner cellular layer. The fibrous layer is made up of dense, irregular connective tissue and contains collagen fibers, blood vessels, and nerve fibers. The inner cellular layer is composed of osteoblasts (bone-forming cells), osteoclasts (bone-resorbing cells), and undifferentiated mesenchymal cells. These cells are responsible for the growth and repair of bone tissue.
The periosteum is richly vascularized, meaning it has an abundant supply of blood vessels, which is essential for its function in bone growth and repair. The periosteum also contains nerve fibers, which provide sensory innervation to the bone and allow for the perception of touch, pressure, and pain.
Location
The periosteum can be found covering the surface of most bones in the body, with the exception of certain areas such as joint surfaces and the articular cartilage (a thin layer of smooth, flexible tissue that covers the ends of bones in a joint). The periosteum is continuous with the fibrous tissue surrounding the joints, known as the joint capsule.
Function
The periosteum plays a vital role in the growth and repair of bone tissue. It contains stem cells, which are undifferentiated cells that can differentiate into different types of cells, including osteoblasts. During bone growth, the stem cells in the periosteum differentiate into osteoblasts and begin to produce new bone tissue.
The periosteum also plays a role in the repair of bone tissue. When a bone is damaged, the periosteum releases signaling molecules that attract immune cells and stimulate the production of new bone tissue. The periosteum also contains blood vessels that can deliver oxygen and nutrients to the site of the injury, aiding in the repair process.
In addition to its role in bone growth and repair, the periosteum also provides support and protection for the underlying bone. It helps to stabilize the bone and prevent it from cracking or breaking under stress. The periosteum also acts as a barrier to prevent bacteria and other foreign substances from entering the bone.
Clinical Significance
There are several clinical conditions and procedures that involve the periosteum.
Periostitis
Periostitis is an inflammation of the periosteum, typically caused by an injury or infection. Symptoms may include pain, swelling, and tenderness along the affected bone. Periostitis is often treated with rest, ice, and nonsteroidal anti-inflammatory drugs (NSAIDs). In severe cases, surgery may be necessary to remove infected tissue.
Osteomyelitis
Osteomyelitis is an infection of the bone and bone marrow, which can spread to the periosteum. Symptoms may include fever, chills, fatigue, and pain in the affected area. Osteomyelitis is typically treated with antibiotics and, in severe cases, surgery to remove infected tissue.
Periosteal stripping
Periosteal stripping is a surgical procedure in which the periosteum is stripped from the surface of a bone. This procedure is often used to treat conditions such as osteomyelitis and non-union fractures (a fracture that fails to heal properly).
During the procedure, the periosteum is carefully stripped from the bone using specialized instruments. The bone is then cleaned and disinfected to remove any remaining infected tissue. The periosteum is then replaced and secured in place using sutures or staples. This procedure helps to stimulate new bone growth and promote healing.
Bone grafting
Bone grafting is a surgical procedure in which bone tissue is transplanted from one area of the body to another. The periosteum is often used as a source of bone tissue for grafting. During the procedure, a small piece of bone with the attached periosteum is removed from the donor site and transplanted to the recipient site. The periosteum helps to stimulate new bone growth and promote healing at the recipient site.
Periosteal elevators
Periosteal elevators are specialized surgical instruments used to lift and manipulate the periosteum during surgical procedures. They are often used in procedures such as bone grafting and periosteal stripping.
