Limb Development

Question 1

Limbs appear as limb buds in week?

Answer 1

4

Question 2

What is the crucial step in limb bud formation

Answer 2

Core of somatic lateral plate mesoderm release GDFs to activate limb bud formation

Question 3

Ectoderm at distal border thickens to form…

Answer 3

Apical ectodermal ridge

Question 4

All other skeletal structures from the neck down develop from?

Answer 4

Sclerotomes of somites

Question 5

Somatic mesoderm and sphlanchnic mesoderm related to which embryonic layers

Answer 5

Ectoderm and endoderm respectively

Question 6

On which body wall do the limbs first appear

Answer 6

Ventrolateral body wall

Question 7

Lower limb buds begin forming how long after?

Answer 7

2 to 3 days after

Question 8

Upper and lower limb buds rotate in which direction

Answer 8

Laterally and medically respectively

Question 9

Positioning along craniocaudal axis regulated by

Answer 9

Homeobox genes

Question 10

Patterning of anterior posterior axis or limb regulated by

Answer 10

Zone polarizing activity

Question 11

Limb outgrowth initiated by which growth factors

Answer 11

TBX5 AND FGF10 in forelimb

TBX4 and FGF10 in hindlimb

Question 12

TBX4, … secreted by?

Answer 12

Lateral plate mesoderm

Question 13

Which factors induce AER

Answer 13

Bone morphogenic proteins from ventricular ectoderm

Question 14

Cells of AER express …. which maintain progress zone for limb growth

Answer 14

FGF4 And FGF 8

NB: other molecules include SHH, WNT7a

Question 15

Proximal distal axis initiated by

Answer 15

Signals from axial structures including the secretion of FGF and later maintained by the AER.

FGF gene produced at apical ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs

Question 16

SUPER IMPORTANT

Answer 16

Slide 22 Limb devt