Bone Growth

Question 1

Differentiation of chondroctues occurs within mesenchymal model.

What do these chondrocytes produce?

Where does this first occur?

What does this lead to?

Answer 1

Chondrocytes produce cartilage

First occuring in the diaphyseal region of humerus and femur

Ultimately the long bones are composed principally of cartilage

Question 2

Where does the primary ossification centre form?

Answer 2

In the diaphysis

Question 3

What does the primary ossification centre do?

Answer 3

Hypertrophy of the chondrocytes

Invasion by blood vessels
-Forming nutrient artery system

Conversion to bone starts circumferentially from the periosteum

Question 4

Where are the secondary ossification centres?

Answer 4

At the epiphyseal regions

Question 5

The process of enchondral ossification in secondary ossification centres occurs via what?

Answer 5

Growth plate

Question 6

What are the two types of ossification?

What are the differences?

Answer 6

Enchondral (endochondral)
-Formation of bone within hyaline cartilage

(Intra)membranous

• Bone forms directly from mesenchymal tissue and does not require a prior cartilage model
• No growth plates
• Occurs in flat bones including the skull bones, clavicle and scapula

Question 7

What are the ossification centres of the elbow?

When do they each form?

Answer 7

C = Capitellum (2y)
R = Radial head (4y)
I = Internal Epicondyle (6y)
T = Trochlea (8y)
O = Olecranon (10y)
E= External epicondyle (12y)

Question 8

Give 2 types of physis (growth plate)

Answer 8

Horizontal (producing longitudinal growth)

Spherical (producing circumferential growth)

Question 9

How are chondrocytes arranged in the physis?

Answer 9

Chondrocytes arranged in layers

Each layer having a different function and destiny

Question 10

What are the 3 layers of the growth plate?

Name the sub layers

Answer 10

Epiphysis
-Zone of reserve

Physis

• Zone of proliferation
• Zone of hypertrophy
• –Maturation
• –Degredation
• –Provisional calcification

Metaphysis

Question 11

Describe the zone of reserve

Cells, function etc

Answer 11

Spherical chondrocytes that are few in number with a large extra-cellular matrix

High concentrations of lipids, glycogen and proteoglycan’s for storage

Bone matrix production

Low pO2

Question 12

What does dwarfism/gigantism effect?

Answer 12

Action of GH which mostly effects zone of proliferation

Proportionate changes in size

Question 13

Mucopolysaccharidosis is a deficiency in which enzyme?

Answer 13

Hydrolase enzyme

Question 14

What are the 4 syndrome types in mucopolysaccharidosis?

Answer 14

Morquio’s
Hurler’s
Hunter’s
Sanfilippo’s

Question 15

What does mucopolysaccardisosis cause?

Answer 15

Proportionate dwarfism

Complex sugars found in urine

Abnormality in Zone of Hypertrophy

Question 16

What is effected in bone by Rickets?

Answer 16

Gross distortion of Zone of maturation

Poorly defined zone of Provisional Calcification

Physeal “cupping” and widening (“champagne glass”)

Bowing of long bones “swiss cheese trabeculae” etc

Question 17

What is multiple epiphyseal dysplasia?

genotype, what is effected, types

Answer 17

Autosomal dominant

Bilateral and symmetrical

Delayed ossification

Severity varies

• Ribbing’s (mild)
• Fairbank’s (severe)

Metacarpals/ tarsals shortened

Early OA in weight-bearing joints