Formation of the Bony Skeleton

Question 0

During Intramembranous Ossification bone develops from what type of CT?

That CT is formed by what type of cell?

Answer 0

Bone develops from fibrous membrane.

Fibrous CT membranes are formed by mesenchyme cells.

Question 1

What are the 2 mechanisms for bone formation?

At week during embryonic development do they start to form?

Answer 1

1. Intramembranous ossification
2. Endochondral ossification

Week 8

Question 2

Intramembranous Ossification occurs where?

Answer 2

Flat bones of the skull, the mandible, and clavicle.

Question 3

What are the stages of Intramembranous Ossification?

Answer 3

1. Mesenchyme cells form fibrous CT = Dense Irregular CT.
2. Ossification center starts in the dense irregular CT.
3. Bone matrix (Osteoid) is secreted within the fibrous membrane).
4. Bone (diploe) & periosteum form.
5. Bone collar of compact bone forms, and red marrow appears.

Question 4

During Endochondral ossification bone develops from what?

Answer 4

Bone forms by replacing hyaline cartilage.

Question 5

Endochondral ossification forms what in the body?

Answer 5

Long bones and most other bones in the body (except flat).

Question 6

Endochondral ossification uses what as its template or model for bone construction?

What must be done prior to ossification?

Answer 6

1. Hyaline cartilage templates.

2. Requires breakdown of hyaline cartilage prior to ossification.

Question 7

What are the stages Endochondral ossification?

Answer 7

1. Mesenchymal cells form hyaline cartilage.
2. Primary ossification center develops in the center of hyaline cartilage - and forms the periosteal (Osteoid) bone collar.
3. Calcification and cavitation of the diaphysis of hyaline cartilage.
4. Diaphysis elongates and medullary cavity forms PLUS the appearance of secondary ossification center in the epiphyses.
   
   • ossification of the epiphyses, with hyaline cartilage remaining only in the epiphyseal plates.