7.1 Cartilage And Endochondral Ossification

Question 1

General composition of cartilage?

Answer 1

Type of CT therefore -

1) specialised cell - chondrocytes
2) Extracellular matrix
- fibres (mostly collagen)
- ground substance (hyaluronan mols made of proteoglycans made of GAGs)

Question 2

What are the three types of cartilage, their composition and examples of where they are found?

Answer 2

1) hyaline
- em - type 2 coll and ground substance
- perichondrium
- e.g. Epiphyseal plates, Trachea, bronchi, larynx,
2) elastic
- perichondrium
- em - type 2 coll, elastic fibres and ground substance
- e.g external ear and epiglottis
3) fibrocartilage
- no perichondrium
- em - type 1 coll and ground substance
- Chondrocytes and fibroblasts
- e.g. Intervertebral discs, pubic symphysis

Question 3

What is the lining around some types of cartilage called and what is its function?

Answer 3

Perichondrium
dense CT that envelopes hyaline and elastic cartilage (not at joint)
contains fibroblast-like cells that differentiate into chondroblasts (flat) and then round up into chondrocytes

Question 4

What is the function of hyaline cartilage?

Answer 4

Reduces friction and absorbs shock

Question 5

In what space do chondrocytes lie in?

Answer 5

Lacuna

Question 6

What fibres do not calcify?

Answer 6

Elastic

Question 7

Describe endochondral ossification. (6)

Answer 7

1. Start with initial hyaline cartilage model
2. Collar of periosteal bone forms
3. Central cartilage calcifies, nutrient artery penetrates bone supplying it with osteoblasts, primary ossification centre formed.
4. Medulla becomes cancellous, cartilage forms epiphyseal growth plates, epiphyses develop secondary ossification centres
5. Epiphysis ossify, growth plates move apart lengthening bone
6. Epiphyseal growth plates replaced by bone, articular cartilage persists

Question 8

Zooming into the growth plates, there are 5 different zones. Name them and their functions.

Answer 8

Zone of reserve cartilage - no proliferation
Zone of proliferation
Zone of hypertrophy - cells enlarge
Zone of calcified cartilage - enlarged cells degenerate as their matrix calcified
Zone of resorption - calcified cartilage turns into bone by osteoblasts function

Question 9

Where is a chondroblast found and what does it do?

Answer 9

In the perichondrium

It allows appositional growth (thickening)

Question 10

Function of fibrocartilage?

Answer 10

Has resilience to act as a shock absorber
Resists shearing
Withstand high pressure

Question 11

Where are the epiphyses, metaphyses and diaphysis?

Answer 11

Epiphyses at ends of bone, metaphyses on other side of growth plate to epiphyses and diaphysis is further in the medulla

Question 12

Describe a synovial joint.

Answer 12

1. Movable joint
2. Bone ends covered by articulating hyaline cartilage
3. Lie within lubricating synovial fluid by articular capsule
4. Lined by synovial membrane

Question 13

What cells are present in the synovial membrane and what is their function?

Answer 13

Macrophages that swallow debris

Fibroblast-like producing synovial fluid

Question 14

Does cartilage have blood vessels that supply to it?

Answer 14

No

Question 15

What is interstitial growth and appositonal growth?

Answer 15

Interstitial growth is where cartilage model grows in length by cell division of chondrocytes and secretion of EM.

Appositional growth is where cartilage model grows in thickness due to addition of more EM on peripheral cartilage surface, accompanied by new chondroblasts developing from perichondrium

Question 16

Function of elastic cartilage.

Answer 16

Structure and support