Diff9 - 16

Question 1

Where does the craniofacial skeleton come from?

Answer 1

Cranial neural crest

Question 2

Where does the axial skeleton come from?

Answer 2

Somites

Question 3

Where does the limb skeleton come from?

Answer 3

Lateral mesoderm

Question 4

What is essential for axial skeleton formation?

Answer 4

Pax1/9

Question 5

What supplements sclerotome formation?

Answer 5

Scleraxis

Question 6

What are involved in patterning of Pax1/9 expression?

Answer 6

SHh and BMP4

Question 7

What are the three steps in axial skeleton formation?

Answer 7

Sclerotome induction, chondrogenesis, osteogenesis

Question 8

Outline sclerotome induction

Answer 8

Question 9

Characterise Pax1 KO

Answer 9

Viable, abnormalities in vertebrae, sternum and scapula

Question 10

Characterise Pax9 KO

Answer 10

Die early, abnormal craniofacial, visceral and limb skeletogenesis

Question 11

Characterise Pax1/9 KO

Answer 11

Completely lack medial sclerotome derivatives

Question 12

Outline transformation from sclerotomal cell to chondroblast

Answer 12

Migration around notochord, down-regulation of Pax1/9, condensation

Question 13

Outline transformation from chondroblast to chondrocyte

Answer 13

Proliferation induced by BMP2/4/5, production of cartilage matrix proteins

Question 14

What does chondroblast production of cartilage matrix proteins require?

Answer 14

Sox9, HMG-box transcription factor

Question 15

What are the two main modes of osteogenesis?

Answer 15

Intramembranous - mainly skull; endochondral - limbs

Question 16

Outline endochondral ossification

Answer 16

Chondrogenesis; chondrocytes cease proliferation, becoming hypertrophic, then dying by apoptosis; blood vessels and osteoblasts enter this space, becoming bone marrow; osteoblasts replace disappearing cartilage and form primary ossification centre; blood vessels enter epiphyses; secondary ossification centres form in epiphyses, leaving cartilaginous growth plate between