18. Limb Development

Question 1

Which of the following statements is not correct about limb formation?

A. The apical ectodermal ridge induces mesodermal differentiation.
B. Paraxial mesoderm forms bone and ligaments of the limbs.
C. Cell death contributes to digit formation.
D. Hind limb buds arise after the forelimb buds.

Answer 1

B. Paraxial mesoderm forms bone and ligaments of the limbs.

Question 2

Which of the following terms describes the absence of limb development? 
A. Syndactyly
B. Polydactyly 
C. Amelia
D. Brachydactyly

Answer 2

C. Amelia

Question 3

Which of the following cells are precursors to the bone (humerus) in the arm?

A. Neural crest cells
B. Surface ectoderm
C. Paraxial mesoderm
D. Lateral plate mesoderm

Answer 3

D. Lateral plate mesoderm

Question 4

All of the following are true statements concerning limb buds except:

A. Apical ectodermal ridge induces mesenchymal differentiation
B. Limb bud mesenchyme forms bone and ligaments
C. Cell death accompanies digit formation
D. The fore limb bud arises after the hind limb bud
E. Syndactyly is caused by abnormal limb bud development

Answer 4

D. The fore limb bud arises after the hind limb bud

Question 5

Both sets of limb bids can first be seen easily during the:

A. 2nd week
B. 3rd week 
C. 4th week 
D. 5th week 
E. 6th week

Answer 5

D. 5th week

Question 6

The extensor musculature of the developing limb

A. Is derived from the Epimere
B. Is supplied by the dorsal primary rami
C. Corresponds to the ventral tip of the abdominal hypomeres
D. Is supplied by the ventral division of the ventral primary rami
E. Is supplied by the dorsal divisions of the ventral primary rami

Answer 6

E. Is supplied by the dorsal divisions of the ventral primary rami

Question 7

The apical mesoderm lays down the segments of the limb in a proximal distal order. The primary inductive influence on the activity of this mesoderm is:

A. The apical ectodermal ridge
B. The notochord
C. The zone of polarizing activity
D. The WNT signaling pathway
E. The sonic hedgehog signaling pathway

Answer 7

A. The apical ectodermal ridge

Question 8

The axial artery of the upper limb is represented in the adult by the axillary and:

A. Radial arteries
B. Brachial arteries
C. Posterior interosseous arteries
D. Anterior interosseous arteries

Answer 8

B. Brachial arteries

Question 9

A child has polydactyly. What embryological mechanism can account for this?

A. Loss of the AER
B. Loss of the ZPA
C. Up regulation of the ZPA
D. Down regulation of the ZPA

Answer 9

C. Up regulation of the ZPA