Cartilage and Osseous Tissue - Quick Review

Lacuna and chondrocyte

• Lacuna: the small cavity that houses a chondrocyte in cartilage.
• Chondrocytes reside in lacunae.
• Ground substance of cartilage includes chondroitin sulfate and glucosamine.
• Ground substance contains thin collagen fibers (not readily seen with common stains).
• Purpose of collagen in the ground substance: provides structural support and tensile strength to cartilage.

Fibrous cartilage (fibrocartilage)

• Examples: menisci of the knee, intervertebral discs, symphysis pubis.
• Common features: strength and durability; chondrocytes in lacunae.
• Matrix: dense collagen fibers to give durability and support.

Elastic cartilage

• Examples: auricle (ear), epiglottis.
• Function: flexibility.
• Chondrocytes in lacunae.
• Matrix: contains elastic fibers to give elasticity.

Osseous tissue

• Compact bone
  • Location: shaft of long bones, outside portions of flat bones.
  • Function: strength and some flexibility.
  • Cells: osteoblasts and osteocytes in lacunae.
  • Relationship: Osteoblasts synthesize the matrix (osteoid) that calcifies to give bone its hardness; bone also contains collagen fibers that contribute to flexibility.
  • Without calcium salts: bone would be soft and nonmineralized, lacking hardness.
  • Without collagen: bone would be brittle and fracture-prone; lacking toughness.
  • Why collagen is essential: provides tensile strength and toughness, enabling bone to resist bending in addition to mineral hardness.