The Skeletal System: Bones, Cartilage, and Ligaments — Structure and Function

The skeletal system provides the body’s framework. Its three main connective tissue components:

1. Bones (Osseous Tissue)

• Hard, mineralized (hydroxyapatite + collagen).
• Functions: support, protection, leverage for movement, mineral reservoir (Ca²⁺, PO₄³⁻), hematopoiesis (marrow), endocrine (osteocalcin, FGF23).
• Types: long, short, flat, irregular, sesamoid.

2. Cartilage

• Specialized avascular connective tissue (chondrocytes in ECM of collagen + proteoglycans).
• Types:
  • Hyaline: articular surfaces, costal cartilage, growth plates, tracheal rings.
  • Fibrocartilage: menisci, intervertebral discs, pubic symphysis — tensile strength.
  • Elastic: pinna, epiglottis, auditory tube — flexibility.
• Functions: smooth joint surfaces, shock absorption, structural templates (growth plates).

3. Ligaments

• Dense regular connective tissue (parallel collagen type I).
• Connect bone to bone across joints.
• Functions: joint stability, limit excessive motion, proprioception (mechanoreceptors).
• Poor vascularity → slow healing.

Integration

Bones leverage, cartilage cushions, ligaments stabilize. Together with tendons (muscle-to-bone) and muscles, they enable controlled movement.