Exam 3: Limb Development 2

Question 1

What cells are the limb bud mesenchyme derived from?

Answer 1

Lateral plate mesoderm

Question 2

What are limb muscles derived from?

Answer 2

Somitic ventral dermomyotomes

Question 3

What causes cartilage formation to be constricted to the central core of the limb bud?

Answer 3

Wnt-7a from overlying ectoderm

Question 4

What is expressed to induce pre-cartilage formation in the limb bud central core?

Answer 4

BMP’s

Question 5

In what direction does differentiation of cartilaginous skeleton occur?

Answer 5

Proximodistal

Question 6

In what direction does digit formation occur?

Answer 6

5 –> 1

Question 7

What marks the point of joint formation?

Answer 7

Condensed zone of cells

Question 8

What inhibits BMP in the region where the joint will form?

Answer 8

Noggin

Question 9

T/F: All components of the joint are formed by skeletal elements.

Answer 9

False, Articular cartilages by skeletal elements & other components by additional mesenchymal cell condensations

Question 10

Which part of the cartilage/bone forming in the limb bud remains intact where the joint forms & forms the joint capsule?

Answer 10

Perichondrium

Question 11

Proximal cells of limb bud produce _____, while pre-muscle cells in the somite express _____.

Answer 11

Scatter factor.

c-met, receptor for scatter factor

Question 12

What do migrating pre-muscle cells express?

Answer 12

Pax-3 & N-cadherin

Question 13

What is pre-muscle cell differentiation in the limb bud dependent on?

Answer 13

Wnt-6 expressed by the ectoderm

Question 14

What is expressed by the connective tissue associated with the muscle masses?

Answer 14

Tcf-4

Question 15

T/F: Individual muscle morphology is determined by connective tissue.

Answer 15

True

Question 16

At what week do motor axons originate from the spinal cord?

Answer 16

5th

Question 17

If the forelimb rudiment is removed, nerves of the brachial plexus are _____ and cells in ganglion may be _____ by up to 50%.

Answer 17

Smaller.

Reduced

Question 18

If an additional limb rudiment is transplanted, what happens to the spinal nerves?

Answer 18

Local spinal nerves supply transplanted limb & increase in thickness.
Ganglia increase as much as 40%

Question 19

If the forelimb rudiment is cut out and transplanted near the original one, _____ nerves are deflected in the direction of the transplanted limb.

Answer 19

Brachial

Question 20

If an additional limb is transplanted next to host limb, _____ nerves develop _____ & they are usually not functional.

Answer 20

Brachial.

Branches

Question 21

Earlly vasculature arises from endothelial cells from _____, _____, & _____.

Answer 21

Aorta, cardinal veins, & angioblasts

Question 22

What inhibits formation of blood vessels?

Answer 22

Overlying ectoderm