Compact bone
Substantia compacta
- Latin synonym: Textus osseus compactus; Substantia corticalis; Cortical bone; Cortex ossis
- Synonym: Dense bone
Definition
Compact bone is the dense, solid form of bone tissue that forms the outer layer of all bones and constitutes the majority of the diaphysis (shaft) of long bones. It is characterized by a tightly organized structure composed of cylindrical units called osteons (or Haversian systems), which consist of concentric lamellae of mineralized collagen fibers surrounding a central Haversian canal containing blood vessels and nerves. The osteons are interconnected by transverse Volkmann’s canals, and the tissue is perforated by a network of canaliculi that facilitate communication between osteocytes embedded in lacunae within the lamellae.
Compact bone provides mechanical strength and rigidity, enabling bones to resist bending and torsional forces. Its hierarchical organization, from mineralized collagen fibrils at the nanoscale to osteons at the microscale, is essential for bone’s biomechanical properties and resistance to fracture.
The compact bone is distinct from trabecular (spongy) bone, which is less dense and found at the ends of long bones and within vertebrae.
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