Bone Components: Epiphysis, Articular Cartilage, Periosteum, and Hyaline Cartilage Explained

These structures are integral to skeletal form and function.

Epiphysis

• Expanded end of a long bone; composed of spongy bone covered by compact bone.
• Articulates with adjacent bone at synovial joint.
• Contains red marrow (hematopoiesis) in adults.

Articular (Hyaline) Cartilage

• Smooth, white, avascular, aneural covering of epiphyseal surfaces.
• Composed of type II collagen + proteoglycans (high water content) → low friction, load distribution.
• No perichondrium; nutrition by synovial fluid diffusion.
• Limited repair capacity (chondrocytes trapped in lacunae).

Periosteum

• Tough fibrous membrane covering all bone surfaces except articular cartilage.
• Two layers: outer fibrous (collagen, Sharpey's fibers → tendons/ligaments), inner cambium (osteoprogenitor cells).
• Functions: bone growth (appositional), fracture repair (callus), vascular/nervous supply, tendon/ligament attachment.

Hyaline Cartilage (General)

• Most common cartilage type: articular surfaces, costal cartilage, nasal septum, tracheal rings, embryonic skeleton.
• Glassy, semi‑transparent; resilience and smooth articulation.
• Precursor to endochondral bone formation.

Relationships

Epiphysis → covered by articular cartilage (a specialized hyaline cartilage) → bathed in synovial fluid. Periosteum covers the metaphysis/diaphysis, stopping at the articular margin.

Together, these tissues enable skeletal growth, joint mechanics, and injury response.