cartilage tissue

Question 1

what is cartilage tissue

Answer 1

• A resilient (elastic) and smooth tissue that comes in different forms and is found in the nose, ear, joints and discs/symphyses of the body

Question 2

cartilage tissue: structure

Answer 2

Structure:

• Chondrocytes (cartilage cells) occupy lacunae (small chambers) embedded in the extracellular cartilage matrix
• Chondrocytes produce and maintain extracellular matrix which is composed of fibres and ground substance (proteoglycans and water)
• This arrangement resists tensile and compressive forces

Question 3

cartilage tissue: key components

Answer 3

• Cartilage is avascular = no blood vessels
• Chondrocytes produce a factor that discourages growth of blood vessels
• Cartilage is aneural = no nerves
• Cartilage gets its nutrition through diffusion (from synovial fluid)
• Components of cartilage extracellular matrix:
  - Collagen fibres
  - Ground substance
  - Proteoglycans
  Chondroitin sulphate, keratin sulphate and hyaluronic acid are the most common GAGs found in cartilage
  - Proteins
  - Water (65-85%)

Question 4

Growth of Cartilage
2 types:
Interstitial
Appositional

Answer 4

Interstitial:
- within
- occurs in physes - in early life
Appositional:
- beside
- hyaline + elastic cartilage gets thicker due to more extracellular matrix and new chondroblasts = new layers

Question 5

Types of cartilage: hyaline cartilage + function

Answer 5

• Found on articular surfaces on synovial joint + end of nose
  → matrix contains large protein fibres that are mostly collagen
  → has a uniform, glossy appearance (resembles glass)
  → provides stiff + somewhat flexible support
  → reduces friction b/w bones
  → found at ends of bones of synovial joints, costal cartilage, larynx, trachea, bronchi, thyroid, nose
  Function:
• bears mechanical stresses without permanent distortion (ie. cushions + absorbs shock)
• smooth surface allows easy sliding movt of bones and minimises shearing
• Resisting friction more than compression (at superficial surface)

Question 6

Types of cartilage: elastic cartilage + function

Answer 6

→ matrix contains numerous (dark-staining) elastic fibres: supportive but bends easily
→ found in external ear, epiglottis

Question 7

Types of cartilage: fibrocartilage + function

Answer 7

→ matrix has little ground substance + numerous, densely interwoven collagen fibres arranged in layers: provides high tensile strength & shock absorption
→ limits movement
→ prevents bone-to-bone contact
→ found b/w pubic bones, intervertebral discs, + the menisci of the knee + articular discs

Question 8

Types of damage to cartilage by wear: interfacial wear

Answer 8

• Wear: removal of material from surfaces by mechanical action
• Synovial joints are particularly susceptible to two different types of wear
  Interfacial wear:
• Damage to articular surfaces caused by lack of lubrication
• This type of wear never occurs in normal joints e.g. occurs in osteoarthritis
• Subchondral bone = bone under the cartilage = now becoming damaged and subchondral bone has lots of nerve fibres in it = hurt

Abrasive: a softer surface is damaged by a harder one
Adhesive: fragments are torn from one surface and adhere to another

Question 9

Types of damage to cartilage by wear: fatigue wear

Answer 9

Fatigue wear:

• Damage to extracellular matrix caused by repetitive loading
• This type of wear occurs in normal joints e.g. high-impact loading injuries

Question 10

repairing cartilage

Answer 10

• Cartilage has limited ability to repair itself
  Why?
• Since cartilage is usually avascular, oxygen + nutrients must diffuse from surrounding tissues (synovial fluid)
• Growth of blood vessels into damaged cartilage is unlikely since forces applied to cartilage are sufficient to collapse capillaries
  Solutions
• Surgical intervention is required, e.g. surgical removal of damaged cartilage + tissue implants
• Once the cartilage is completely destroyed joint replacement is one option