U2 Lecture 4

Question 1

Types of growth of cartilage

Answer 1

Interstitial and appositional growth

Question 2

Define interstitial growth

Answer 2

• growth from within (cartilage)

- growth in length at epiphyseal plate

Question 3

Steps of interstitial growth

Answer 3

1. Chondroblasts build matrix and differentiate into chondrocytes
2. Chondrocytes divide
3. chondrocytes build matrix and spread apart
4. Cartilage tissue grows from within

Question 4

Zones for growth in the epiphyseal plate

Answer 4

Epiphysis

1. resting cartilage
2. proliferating cartilage
3. hypertrophic cartilage
4. calcified cartilage

Diaphysis

• epiphysis and diaphysis are the outer layers of bone

Question 5

What zone of cartilage is new chondrocytes formed?

Answer 5

proliferating cartilage

Question 6

What happens in calcified cartilage?

Answer 6

old chondrocytes are replaced by bone

Question 7

Growth at epiphyseal plate summary

Answer 7

1. Diaphyseal osteoclasts break down calcified cartilage
2. osteoblasts lay down spongy bone
3. chondrocytes will continue to form cartilage matrix at the proliferating cartilage region
4. growth in length stops when the osteoclasts/ osteoblasts work faster than the chondrocytes in the proliferating zone -> epiphyseal plate closes and becomes the epiphyseal line

Question 8

Define Appositional growth

Answer 8

• growth in width
• periosteal osteoblasts build bone on outer surface of bone and endosteal osteoblasts increase the diameter of the marrow cavity
• both bone diameter and cortical width increase

Question 9

What does appositional growth do?

Answer 9

It generates new osteons to the periosteal side of the bone

Question 10

Steps of appositional growth

Answer 10

1. ridges in periosteum create groove for periosteal blood vessel
2. periosteal ridges fuse, forming an endosteum-lined tunnel
3. osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel forming a new osteon
4. bone grows outward as osteoblasts in periosteum build new lamellae. repeats as ridges fold over blood vessels