W6 Anatomy And Histology Of Joins And Ossification

Question 1

Describe the process of ossification

Answer 1

• progenitor cells form osteoblastic lines
• these cells of the lines proliferate
• maturation of the matrix
• matrix mineralises, forming bone

Question 2

What is ossification?

Answer 2

Development of new bone

Question 3

What is intramembranous ossification?

Answer 3

When mesenchymal gets converted straight to bone.

Faster process. No cartilage state in between, direct conversion.

Question 4

Give examples of bones formed by intramembranous ossification.

Answer 4

Flat bones of the skull, most facial bones, mandible

Question 5

Describe the process of intramembranous ossification.

Answer 5

1. in the ossification centre, the mesenchymal cells get converted to osteoblast cells, which secrete the organic extracellular matrix
2. calcification: calcium and other mineral salts are deposited and extracellular matrix calcifies
3. formation of trabeculae: extracellular matrix develops into trabeculae that fuse to form spongy bone
4. development of the periosteum: mesenchyme at the periphery of the bone develops into the periosteum. Forms outer layer periosteum, then compact bone, then spongy bone in the middle.

Question 6

What is a fontanelle?

Answer 6

In infants, the space where two sutures join forms a membrane covered ‘soft spot’ called a fontanelle. Allow for growth of brain and skull, and moulding at time of birth. Close slowly after birth.

Question 7

What fontanelle are in infants and how many?

Answer 7

Anterior fontanelle, anterolateral fontanelle, posterolateral fontanelle, posterior fontanelle
There are 6 in total

Question 8

When does the anterior fontanelle close?

Answer 8

After 18 months

Question 9

What is endochondral ossification?

Answer 9

Formation of bone

Membrane converted to cartilage, cartilage replaced by bone

Question 10

Describe the process of endochondral ossification (16:00)

Answer 10

1. Fetal hyaline cartilage model develops from mesenchyme
2. Cartilage calcified and a periosteal bone collar forms around diaphysis
3. Primary ossification centre forms in the diaphysis
4. Secondary ossification centre form in the epiphyses
5. Bone replaces cartilage, except the articular cartilage and epiphyseal plates
6. Epiphyseal plates ossify and form epiphyseal lines

Question 11

What parts of the skull develop by the different ossifications?

Answer 11

Skull base by endochondral ossification

Skull vault by membranous ossification

Question 12

What is achondroplasia?

Answer 12

The endochondral ossification of the skull is affected. Skull vault grows normally, but base remains small. So foramen magnum develops narrowly and can cause compression on the spinal cord.

Question 13

What are the different layers of the growth plate/epiphyseal growth plate?

Answer 13

Zone of resting cartilage
Zone of proliferation
Zone of hypertrophy
Zone of calcification and cell death
Zone of ossification