Csonthártya

Csonthártya, known in English as the periosteum, is a dense, vascular connective tissue layer that covers the outer surface of most bones, except where cartilage lines the joints. It forms a continuous envelope around bone and serves as both a protective covering and an interface with surrounding tissues.

The periosteum consists of two layers. The outer fibrous layer contains collagen fibers, fibroblasts, and a rich supply of nerves, providing mechanical protection and serving as an attachment site for tendons and ligaments. The inner cambial, or osteogenic, layer harbors osteoblasts and progenitor cells capable of forming new bone and participating in growth and repair.

Functions of the periosteum include nourishing the underlying bone through blood vessels that accompany nerves and extend into the cortex, and enabling growth in bone diameter (appositional growth) via the activity of osteoblasts in the inner layer. During fracture healing, periosteal progenitor cells contribute to callus formation and accelerate repair.

Clinical significance includes periostitis, inflammation of the periosteum that can follow trauma, infection, or overuse. The periosteum participates in the pathology of osteomyelitis, and radiographs may show a periosteal reaction in various conditions. In children, the periosteum is relatively thick and highly active, influencing healing capacity and growth.

In summary, the periosteum is a critical structure for bone protection, nutrition, growth, and repair, with distinct fibrous and osteogenic layers and significant clinical relevance across age groups.