The Periosteum
The periosteum is a thin fibrous membrane that covers the outer surface of bone in all locations except at articular surfaces (joints), tendon insertions, and sesamoid bone surfaces. 1, 2
Anatomical Structure
The periosteum consists of two distinct layers 1, 2:
- Outer fibrous layer: A firm, collagen-filled layer containing fibroblasts that provides structural support and protection 1, 2
- Inner cambium (proliferative) layer: Contains osteoprogenitor cells that differentiate into osteoblasts responsible for bone formation, remodeling, and width increase 1, 2
Attachment and Blood Supply
- The periosteum is anchored to underlying bone by strong collagenous fibers called Sharpey's fibers, which extend into the outer circumferential and interstitial lamellae of bone 2
- Four vascular systems supply the periosteum: the intrinsic periosteal system (between the two layers), periosteocortical (main nutritional supply), musculoperiosteal (callus formation after fractures), and fascioperiosteal (bone-specific) 1
Clinical Significance
- Unlike bone itself, the periosteum contains nociceptive nerve endings, making it highly sensitive to manipulation and a source of pain in bone pathology 2
- The periosteum serves as a reservoir of osteogenic cells critical for bone healing after fractures, with progenitor cells developing into osteoblasts and chondroblasts 2
- In children, the periosteum is looser and more elastic compared to adults, resulting in earlier and more exuberant reactions to injury or disease 1
- Swelling becomes clinically apparent only when tumors or infections progress through the cortex and distend the periosteum 3