Cartilage

Question 1

What is the only cell type found in hyaline cartilage?

Answer 1

Chondrocytes

• If recently divided in small clusters called isogenous groups
• The chondrocytes within the isogenous groups separate as they lay down extracellular matrix

Question 2

What role does hyaline cartilage have in bone development?

Answer 2

• In early foetal development, hyaline cartilage is the precursor model of those bones that develop by endochondrial ossification
• As long bones develop, some hyaline cartilage remains at the articulating surface (and also at the epiphyseal growth plate until bone growth ceases)

Question 3

What is the structure of hyaline cartilage?

Answer 3

• Avascular
• Extensive extracellular matrix in which lie chondrocytes
• Chondrocytes produce and maintain the extracellular matrix (solid and firm but also pliable due to high water content so is resilient to repeated pressure)
• Hyaluronic acid assists resilience to repeated application of pressure

Question 4

Where is hyaline cartilage found?

Answer 4

Found in articulating joints:

• Nose
• Intervertebral disc
• Costal cartilage
• Knee joints

Question 5

What covers hyaline cartilage?

Answer 5

Perichondrium cover the margin of hyaline cartilage (top and bottom)
- Perichondrium is a dense connective tissue

Question 6

What does hyaline cartalige contain?

Answer 6

• Contains elongated fibroblast-like cells that can develop into chondroblasts and then into chondrocytes
• Chondrocytes lying cartilage extracellular matrix which they produce and maintain:
  
  • Growth from the periphery known as APPOSITIONAL GROWTH
  • Growth from the centre known as INTERSTITIAL GROWTH

Question 7

What is the histology of hyaline cartilage stained with H&E?

Answer 7

• Pink layer = dense connective tissue containing fibroblasts and collagen 1
• Lighter pink layer = perichondrium
• White layer = Growing cartilage (appositional growth)
• Purple layer = Cartilage and extracellular matrix (highly hydrated which leads to resilient and non-compressible characteristics

Question 8

What are the layers of cartilage during growth at epiphyseal plate (oldest –> newest)?

Answer 8

Zone of resorption
- Calcified matrix is in direct contact with marrow cavity
- Small blood vessels and connective tissue invade the region occupied by
the dying chondrocytes leaving the calcified cartilage as spicules between
them.
- Bone is laid down on these cartilage spicule

Zone of calcified cartilage
- Enlarged cells begin to degenerate and matrix calcifies

Zone of hypertrophy

• Cells enlarge
• Matrix compressed into linear bands between cell columns

Zone of proliferation
- Cells actively dividing to form columns, cells enlarge and secrete matrix

Zone of reserve cartilage
- No cellular proliferation or active matrix production