Topic 29 - Osteogenesis: Desmal ossification

Question 1

What is demsmal ossification and what does it form?

Answer 1

• Bones form directly from layer of embryonic mesenchyme to bones.
• Intramembranous.
• Forms calvarium bones.

Question 2

Process:?

Answer 2

1. Capillaries invade site.
2. Mesenchymal cells become spherical, forming osteoprogenitor cells.
3. Osteoprogenitor cells form osteoblasts (bone-forming cells).
4. Osteoblasts synthesize and secrete osteoid, causing mineralization.
5. Osteoblasts surrounded by osteoid transform into osteocytes.

Question 3

Formations:?

Answer 3

• Ossification center.
• Bony spiracles and trabeculae.
• Immature bone (trabecular, spongy, or cancellous).
• Eventually replaced by mature lamellar bone.