Limb Development

Question 1

What are HOX genes?

Answer 1

Genes conserved through evolution that help with development and growth

Question 2

When is organogenesis complete?

Answer 2

Week 8

Question 3

When is the trilaminar disc stage?

Answer 3

Day 17

Question 4

Cartilage and bone is formed from the

Answer 4

intermediate mesoderm

Question 5

Limb buds are an outpouching of the

Answer 5

ventrolateral body wall

Question 6

The paraxial mesoderm forms somites which differentiate into

Answer 6

muscles of the limbs

Question 7

Limb musculature is innervated by

Answer 7

the ventral rami of spinal nerves

Question 8

The posterior condensation gives rise to

Answer 8

extensors

Question 9

The UL is innervated by the

Answer 9

brachial plexus (C5-T1)

Question 10

The LL is innervated by the

Answer 10

sciatic nerve (L4-S3)

Question 11

Limb patterning occurs in how many planes?

Answer 11

3
proximodistal
craniocaudal
dorsoventral

Question 12

What is secreted by the mesenchyme to induce the formation of the AER?

Answer 12

FGF10

Question 13

What FGF does the AER express?

Answer 13

FGF 4 and FGF 8

Question 14

The area underneath the AER is known as the

Answer 14

proliferation zone

Question 15

Failure of the AER in the central part of the limb bud leads to

Answer 15

cleft hand/foot

Question 16

Supernumerary limbs are induced by

Answer 16

ectopic FGF

Question 17

The fact that the thumb is lateral and the little finger is medial can be explained by

Answer 17

craniocaudal patterning

Question 18

The ZPA can be found in the

Answer 18

caudal part of the limb bud

Question 19

A high concentration of SHH causes

Answer 19

the growth of caudal structures

Question 20

The dorsal ectoderm expresses what

Answer 20

Wnt7, which activates LMX1B