CARTILAGE - Basics

Question 1

What is cartilage made up of (2)?

Answer 1

Cells (chondrocytes [and fibroblasts in fibro])

Extracellular Matrix

Question 2

What is the ECM made up of for hyaline, elastic and fibrocartilage?

Answer 2

Hyaline - Proteoglycans, Hyaluronic acid, Type II collagen
Elastic - Proteoglycans, Hyaluronic acid, Type II collagen, Elastic fibres
Fibro - Proteoglycans, Hyaluronic acid, Type I and II collagen

Question 3

What role does Hyaluronic acid have?

Answer 3

It is resilient to compression (needed in cartilage) and also suggested to have a lubricating effect

Question 4

What property about GAGs helps form a watery gel ECM? How does this help cartilage be resilient to pressure?

Answer 4

They are negatively charged so attract H20 forming a gel. Cartilage (esp hyaline) is resistant to pressure because of 1) Hydrated ECM and 2)Transient movement of the H20

Question 5

How do substances get in if cartilage is avascular?

Answer 5

The high ratio between GAGS:Type II collagen allows for diffusion of substances between chrondrocytes and surrounding blood vessels.

Question 6

What cells do Hyaline, Elastic and Fibrocartilage have? What types of collagen?

Answer 6

Hyaline - Chondrocytes, Type II
Elastic - Chondrocytes type II
Fibro - Chondrocytes & Fibroblasts type I and some II

Question 7

What is the direction of growth for cartilage?

Answer 7

Direction of growth is from periphery inwards - Appositional

Question 8

What are isogenous groups (structure/function)

Answer 8

Groups of chondrocytes (recently undergone mitosis) that are clustered together. Helps cartilage grow by secreting ECM, which causes interstitial growth and they become further apart.

Question 9

What is the perichondrium?

Answer 9

Layer of dense connective tissue - contains elongated fibroblast-like cells

Question 10

What is the role of chrondrocytes? From which cells are they formed from?

Answer 10

Secrete and maintain EC matrix.

Formed from chrondroblasts - derived from embryonic stem cells

Question 11

Which areas are there no perichondrium? (3 - 2 areas in the body and one type of cartilage)

Answer 11

• Articulating surfaces
• Epiphyseal growth plate
• Fibrocartilage

Question 12

Which types of cartilage calcify with age and which dont?

Answer 12

Hyaline does

Elastic and Fibrocartilage don’t

Question 13

Do adult chondrocytes continue to undergo mitosis and interstitial growth?

Answer 13

No

Question 14

Give some examples of where fibrocartilage is found? What is a common about all these areas that makes having fibrocartilage important?

Answer 14

• Vertebral discs
• Articular discs of sternoclavicular and temporomandibular joints
• Menisci of knee
• Pubis synthesis

They all withstand shock and resist shearing.

Question 15

What is endochondrial ossification? When does it occur until?

Answer 15

Replacement of hyaline with bone - most bones form this way. Stops when puberty finishes/adult skeletally mature.

Question 16

What are the 6 stages of endochondrial ossification? What occurs at each?

Answer 16

1) 5 wks gestation - cartilage model of bone
2) 6-8wks - collar of periosteal bone forms at shaft
3) 8-12wks - a)central cartilage calcifies b)artery supply brings osteogenic cells c)primary ossification centre formed
4) postnatal - a)medulla becomes cancellous bone b)cartilage forms growth plates c)epiphyses develop secondary centres for ossification
5) prepubescent - a)epiphises ossify b)growth plates move apart c)bones lengthen
6) adult - a)epiphyseal growth plates replaced by bone b)hyaline articular cartilage persists.

Question 17

Define osteocyte, osteoclast, osteoblast

Answer 17

Osteocyte - mature bone cell when an osteoblast is embedded into the EC matrix it has secreted

Osteoblast - builds bone - Deposits
Osteoclast - Resorbs bone

Question 18

What are the 5 zones of cells through the epiphyseal growth plate and what do they do?

Answer 18

1) Zone of reserve cartilage - no cellular prolif
2) Zone of prolif - prolif and EC matrix secreted
3) Zone of hypertrophy - cells enlarge
4) Zone of calcified cartilage - degenerate and matrix calcifies
5) Zone of resorption - calcified matrix is in direct contact with the marrow cavity - blood vessels and connective tissue innate where dying chondrocytes are and leave calcified cartilage as spicules. Bone is laid down on these spicules.