Cartilage

Question 1

What is cartilage? (2)

Answer 1

• Cartilage is a form of connective tissue composed of chondrocytes and specialized ECM
• Avascular

Question 2

What is the ECM of cartilage? (3)

Answer 2

o Solid and firm but pliable matrix, making it resilient
o Large amounts of GAGs compared to type II collagen
- allows for diffusion between blood vessels in the surrounding connective tissue and the chondrocytes within the matrix
o Large amount of hydrated proteoglycans make the matrix weak in shear (resists tearing)

Question 3

Hyaline cartilage:
Location
Function
Presence of perichondrium
Undergoes calcification
Main cell type present
Characteristic features of ECM

Answer 3

Question 4

Elastic cartilage:
Location
Function
Presence of perichondrium
Undergoes calcification
Main cell type present
Characteristic features of ECM

Answer 4

Question 5

Fibrocartilage:
Location
Function
Presence of perichondrium
Undergoes calcification
Main cell type present
Characteristic features of ECM

Answer 5

Question 6

What is the hyaline cartilage matrix defined by? (4)

Answer 6

• Categorized by matrix containing
  o Type II collagen fibers
  o GAGs
  o Proteoglycans
  o Multi-adhesive glycoproteins

Question 7

What are chondrocytes? (2)

Answer 7

o Can be found singularly or in isogenous groups
o In isogenous groups, they indicate that the cells
have recently divided

Question 8

What are the Regions of the hyaline cartilage matrix? (3)

Answer 8

1. Capsular (pericellular) matrix
2. Territorial matrix
3. Interterritorial matrix

Question 9

What is the Capsular (pericellular) matrix?

Answer 9

o Ring of more densely staining matrix located
immediately around the chondrocyte

Question 10

What is the territorial matrix?

Answer 10

o Surrounds the isogenous groups and stains less intensely than capsular matrix

Question 11

What is the Interterritorial matrix? (2)

Answer 11

o Surrounds territorial matrix
o Occupies the space between groups of chondrocytes

Question 12

What is the Perichondrium? (3)

Answer 12

o Firmly attached dense irregular connective tissue composed of cells that are indistinguishable from fibroblasts
o Source of new cartilage cells
o When actively growing perichondrium appears in 2 layers
- Inner cellular layer containing chondroblasts
- Outer fibrous layer

Question 13

What are the features of articular cartilage? (2)

Answer 13

o No perichondrium present
o Exhibits zonation for specific functions

Question 14

What are the zones of articular cartilage? (4)

Answer 14

1. Superficial (tangential) zone
2. Intermediate (transitional) zone
3. Deep (radial) zone
4. Calcified zone

Question 15

What is the Superficial (tangential) zone? (3)

Answer 15

o Pressure resistant region closest to articular surface
o Chondrocytes are elongated and flattened
o Type II collagen arranged parallel to free surface

Question 16

What is the Intermediate (transitional) zone? (2)

Answer 16

o Below superficial zone
o Round, randomly distributed chondrocytes

Question 17

What is the deep (radial) zone?

Answer 17

o Small, round chondrocytes arranged in short columns
perpendicular to free surface

Question 18

What is the calcified zone? (2)

Answer 18

o Calcified matrix with small chondrocytes
o Tidemark separates deep zone from calcified zone

Question 19

How is elastic cartilage distinguished? (3)

Answer 19

• Distinguished by the presence of elastin in the cartilage matrix
• All other components are the same as that of hyaline cartilage
• Does not calcify with the ageing process

Question 20

What is fibrocartilage? (4)

Answer 20

• Combination of hyaline cartilage and dense regular connective tissue
• Chondrocytes dispersed among collage fibers singularly/in rows/in isogenous groups
• No perichondrium present
• Has type I and II collagen fibers

Question 21

What is Chondrogenesis? (4)

Answer 21

• Mesenchymal chondroprogenitor cells differentiate into chondroblasts
• These chondroblasts secrete cartilage matrix
• When they are completely surrounded by matrix, they are called chondrocytes
• Mesenchymal tissue immediately surrounding chondrogenic nodules give rise to perichondrium

Question 22

What are the types of cartilage growth? (2)

Answer 22

1. Appositional growth
2. Interstitial growth

Question 23

What is appositional growth? (5)

Answer 23

• Forms new cartilage at the surface of an existing cartilage
• Requires perichondrium
• New cartilage cells are derived from the inner portion of the surrounding perichondrium
• Cells resemble fibroblasts in form and function
  o They produce type I collagen
• When cartilage growth is initiated, these cells differentiate

Question 24

What is interstitial growth? (2)

Answer 24

• New cartilage is formed within an existing cartilage mass
• New cartilage cells arise from the division of chondrocytes within their lacunae

Question 25

How is interstitial growth possible? (4)

Answer 25

This is only possible because:
o The chondrocytes retain their ability to divide
o The surrounding matrix is distensible allowing for cell secretory activity
* As new matrix is secreted, a partition is formed between daughter cells and they each occupy their
own lacuna
* The daughter cells mover further apart as more matrix is secreted

Question 26

Why is cartilage repair limited? (3)

Answer 26

o Avascularity
o Immobility of chondrocytes
o Limited ability of mature chondrocytes to proliferate

Question 27

When can cartilage repair occur? (2)

Answer 27

• Repair can occur but only if defect involves perichondrium
• Repair mostly involves production of dense connective tissue

Question 28

What is Osteoarthritis? (2)

Answer 28

• Degenerative, age-related joint disease characterized by
  o Chronic joint pain
  o Destruction of articular cartilage