Skeletal Cartilages

Introduction

• Cartilage is a type of skeletal tissue.
• Most of the skeleton initially starts as cartilage, especially in embryos and fetuses.
• Cartilage remains in areas requiring flexibility, e.g., rib cage.

Characteristics of Skeletal Cartilage

• Made of resistant, molded cartilage tissue, primarily water.
• Lack of blood vessels and nerves, hence no bleeding or pain.
• Nutrient supply via surrounding perichondrium.
  • Perichondrium: Dense connective tissue that surrounds cartilage, resists outward expansion, and contains blood vessels for nutrient delivery.

Composition

• Made of chondrocytes: mature cartilage cells in small cavities (lacunae).
• Chondrocytes maintain the jelly-like extracellular matrix of cartilage.

Types of Cartilage

1. Hyaline Cartilage

   • Provides support, flexibility, and resilience.
   • Most abundant, contains collagen fibers.
   • Locations: joints (ends of bones), ribs, larger airways (larynx, trachea), nasal cartilage.

2. Elastic Cartilage

   • Similar to hyaline but with more elastic fibers.
   • Locations: external ear, epiglottis.
   • Function: Allows flexibility and recoiling to original shape.

3. Fibrocartilage

   • Toughest type due to thick collagen fibers.
   • High tensile strength, resists compression.
   • Locations: menisci of knee, intervertebral discs, pubic symphysis.
   • Function: Provides structural support, allows for slight movement and flexibility.

Growth of Cartilage

• Appositional Growth

  • Occurs in perichondrium, new matrix laid down at cartilage surface.
  • Analogous to the layering of pearls.

• Interstitial Growth

  • New cartilage forms from within.
  • Similar to tree growth, new material found deeper within.

Calcification of Cartilage

• Occurs during normal bone growth and aging.
• Can calcify due to injury or trauma, leading to hardened cartilage.
• Calcified cartilage is not true bone due to its avascular nature.