S12) Cartilage

Question 1

What is cartilage?

Answer 1

Cartilage is an avascular tissue that consists of an extensive extracellular matrix in which lie chondrocytes

Question 2

What are chondrocytes and what do they do?

Answer 2

The chondrocytes are cartilage cells which produce and maintain the extracellular matrix

Question 3

What is the role of glycosaminoglycans?

Answer 3

GAGs permit ready diffusion of substances between the chondrocytes and the blood vessels surrounding the cartilage

Question 4

Describe the structure of the extracellular matrix

Answer 4

The extracellular matrix is solid and firm, but also rather pliable and therefore resilient to the repeated application of pressure (hyaluronic acid assists this)

Question 5

Explain how the structure of the extracellular matrix is adapted to its function

Answer 5

High hydration & transient movement of water in the matrix, permits resilience to varying pressure loads

Question 6

Identify and distinguish between the structure of the three types of cartilage

Answer 6

• Hyaline cartilage: matrix containing proteoglycans, hyaluronic acid and type II collagen

- Elastic cartilage: matrix like hyaline cartilage but with many elastic fibres and elastic lamellae

- Fibrocartilage: matrix like hyaline cartilage but with abundant type I collagen fibres

Question 7

Where can hyaline cartilage be found?

Answer 7

• Nose cartilage
• Articular cartilage of joint
• Costal cartilage
• Trachea cartilage

Question 8

The only cell type in hyaline cartilage is the chondrocyte.

Describe its role and properties

Answer 8

• Chondrocytes are present singly or, if recently divided, as small clusters called isogenous groups
• The chondrocytes within the isogenous groups separate as they lay down extracellular matrix

Question 9

Explain the role of hyaline cartilage in bone development

Answer 9

In early foetal development, hyaline cartilage is the precursor model of those bones which develop by endochondral ossification

Question 10

What is the role of the perichondrium?

Answer 10

• Fibroblast-like cells of the perichondrium give rise to flat, new formed chondroblasts
• The chondroblasts secrete matrix components and round up to develop into chondrocytes

Question 11

In terms of cartilage, distinguish between appositional and interstitial growth

Answer 11

- Appositional growth: involves an increase in width due to growth from the periphery (perichondrium)

• Interstitial growth: involves an increase in length due to the deposition of further matrix by isogenous groups deeper in the cartilage

Question 12

What do chondrocytes lie in?

Answer 12

Each chondrocyte lies in a lacuna (pl. lacunae)

Question 13

Where can elastic cartilage be found ?

Answer 13

• External ear (pinna)
• Epiglottis

Question 14

Explain how elastic cartilage differs from that of hyaline

Answer 14

• The many elastic fibres confers elasticity upon the cartilage, in addition to the resilience of hyaline cartilage
• Elastic cartilage does not calcify (hyaline calcifies with age)

Question 15

Where can fibrocartilage be found?

Answer 15

• Intervertebral discs
• Pubic symphysis
• Sternoclavicular joint
• Meniscus

Question 16

What are the cell types found in fibrocartilage?

Answer 16

• Chondrocytes
• Fibroblasts

Question 17

Explain how fibrocartilage differs from hyaline cartilage

Answer 17

• Fibrocartilage is a combination of dense regular connective tissue and hyaline cartilage
• The cells are often distributed in rows and there is no surrounding perichondrium

Question 18

What is the primary function of fibrocartilage?

Answer 18

Fibrocartilage has the resilience to act as a shock absorber and to resist shearing forces