periostio

Periostio, in English known as the periosteum, is a dense, double-layered membrane that covers most of a bone’s exterior surfaces, except where articular cartilage is present. It consists of an outer fibrous layer and an inner cambial (osteogenic) layer. The fibrous layer provides structural protection and serves as an attachment site for tendons and ligaments, while the cambial layer contains osteoprogenitor cells capable of differentiating into osteoblasts during growth and repair.

The periosteum is highly vascularized and innervated. Blood vessels from surrounding tissues perforate the outer layer and supply the cortex, while nerves convey sensory information, contributing to pain perception in fractures and other injuries. The periosteum also anchors to the bone via Sharpey's fibers, which are collagen fibers that extend from the periosteum into the cortical bone.

Functions and growth: The periosteum protects bone and supplies nutrients necessary for bone health. The inner osteogenic layer participates in appositional or circumferential growth and plays a key role in fracture healing by providing osteoblasts that contribute to new bone formation. It also serves as an attachment point for tendons and ligaments, aiding in movement and force transmission.

Clinical notes: In children, the periosteum is relatively thick and more osteogenic, contributing to rapid bone growth and healing. Injury to the periosteum can cause significant pain and swelling. Periostitis is inflammation of the periosteum and can occur with repetitive strain, infection, or deficiencies such as scurvy; imaging may show periosteal reaction or new bone formation along the cortex in some conditions.