Lect. 22 - Skeletal System Devpt. I Flashcards Preview

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Flashcards in Lect. 22 - Skeletal System Devpt. I Deck (16):
1

What parts of the skeleton originate in the lateral plate mesoderm?

Limb bones and girdles

2

What parts of the skeleton originate in the head mesoderm?

Calvaria and base of skull

3

What parts of the skeleton originate in the neural crest?

Facial bones

4

Describe the common pathways of the bone/cartilage differentiation pathways

Mesenchyme is induced to enter the common pathway; production of N-cadherins which promote mesenchymal cell condensation; TGF-beta stimulates synthesis of fibronectin and N-CAM; aggregated state of mesenchymal cells is stabilized.

5

Describe the membranous bone pathway of the bone/cartilage differentiation pathways.

Requires TFs Runx-2 and Osx; mesenchymal cells differentiate into osteoblasts

6

Describe the permanent cartilage pathway of the bone/cartilage differentiation pathways.

Mesenchymal condensation forms chondroblasts; Sox-9 causes chondroblasts to secrete collagen II and cartilage matrix; Sox-9 is continually expressed in permanent cartilage.

7

Describe the endochondral bone pathway of the bone/cartilage differentiation pathways.

Runx-2, ihh, and BMP-6 induce this cartilage to undergo hypertrophy; hypertrophic cartilage cells secrete bone proteins and vascular endothelial growth factor; invading blood vessels erode the hypertrophic cartilage and bring in osteoblasts to replace cartilage w/ bone

8

Origin of the centrum

Derived from ventral and medial parts of paired scleretomes

9

Origin of neural arches

Arise from dorsal regions of sclerotomes

10

Origin of costal processes/ribs

Proximal development depends on expression of myotonic myogenic factors, Myf-5 and Myf-6; distal development depends on BMP signals from somatopleural mesoderm

11

Occipital-cervical boundary

Hox 3

12

Cervical-thoracic boundary

Hox 6

13

Attached-floating ribs boundary

Hox 9

14

What is the origin of the sternum?

Derived from lateral plate mesoderm; arises as a pair of cartilaginous bands that fuse then subdivides into craniocaudal elements

15

What is the origin of the clavicle?

Arises from neural crest; follow intramembranous pathway; one of the first bones to become ossified

16

What parts of the skeleton originate in the mesodermal scleretomes (of somites)?

Vertebral column, ribs, sternum