Development of the Limbs

Question 1

What do the upper and lower limb buds form from?

Answer 1

somatopleuric lateral plate mesoderm

Question 2

What are the two layers that each limb bud contains?

Answer 2

outer ecctodermal cap

inner mesodermal core

Question 3

What layer of differentiated ectoderm induces differentiation throughout the limb?

Answer 3

Apical ectodermal ridge (AER)

Question 4

What determines which limb segments will form?

Answer 4

The amount of time mesenchyme is under influence of AER

Question 5

What layer subdivision gives rise to bones, tendons, lligaments and vasculature of the limb?

Answer 5

Lateral plate mesoderm

Question 6

What layer subdivision gives rise to muscles of the limb?

Answer 6

Somitic mesoderm

Question 7

Appendicular skeleton forms by endochondral ossification from condensations of _______?

Answer 7

lateral plate mesoderm

Question 8

During the 5th week somitic mesoderm invades limb bud and forms a dorsal and ventral mass. What forms out of these masses?

Answer 8

Myoblasts – which then form the muscles of the limbs

Question 9

Which way does the upper limb rotate?

Answer 9

laterally

Question 10

Which way does the lower limb rotate?

Answer 10

medially

Question 11

How do the limb muscles get innervation?

Answer 11

Motor axons arising from the spinal cord enter the limb buds and grow into the dorsal and ventral muscle masses

Question 12

Are the limbs innervated by dorsal or ventral primary rami?

Answer 12

Ventral rami

Question 13

_________ enter the limb buds after the motor axons and use them for guidance

Answer 13

sensory axons