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Flashcards in Ch. 10 Book Questions Deck (10)
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1

Which of the following molecules plays an important role in the determination of the dorsoventral axis of the developing limb?
a. Msx-1
b. Wnt-7a
c. Hoxd-13
d. Pax-1
e. FGF-8

b. Wnt-7a

2

What molecule is associated with myogenic cells migrating into the limb bud from the somites?
a. shh
b. BMP-7
c. FGF-4
d. Pax-3
e. En-1

d. Pax-3

3

What is the principal function of the AER?
a. Stimulating outgrowth of the limb bud
b. Setting up the anteroposterior axis of the limb bud
c. Determining the specific characteristics of the ectodermal appendages of the limb
d. Determining the pattern of neural ingrowth into the limb
e. Attracting the subcutaneous plexus of capillaries in the limb bud

a. Stimulating outgrowth of the limb bud

4

In the developing limb the sonic hedgehog (shh) gene product is produced in the:
a. Progress zone
b. Region of interdigital cell death
c. ZPA
d. AER
e. Common muscle mass

c. ZPA

5

The connective tissue of the limb arises from the:
a. Paraxial mesoderm
b. Neural crest
c. Intermediate mesoderm
d. Somitic mesoderm
e. Lateral mesoderm

e. Lateral mesoderm

6

The formation of clubfoot (talipes equinovarus) is associated with:
a. A misplaced ZPA
b. Defective cellular migration from somites
c. Thalidomide
d. Oligohydramnios
e. A neural crest defect

d. Oligohydramnios

7

An infant whose mother underwent chorionic villus sampling during pregnancy was born with the tips of two digits missing. What is a possible cause?

A tear of the amnion during the chorionic villus sampling procedure could have resulted in an amniotic band wrapping around the digits and strangulating their blood supply, thereby causing the tips to degenerate and fall off.

8

A woman who underwent amniocentesis during pregnancy gave birth to a child with a duplicated thumb. What is a possible cause?

This defect is unlikely to be related to the amniocentesis procedure because the morphology of the digits is well established by the time such a procedure is undertaken (usually around 15 to 16 weeks). The most likely cause is a genetic mutation.

9

If the somites close to a limb-forming region are experimentally removed, the limbs form without muscles. Why?

Muscle-forming cells arise from the somites.

10

A child is born with webbed fingers (syndactyly). What is the reason for this anomaly?

The immediate cause is likely the absence of programmed cell death in the interdigital mesoderm. The cause of the disturbance in cell death is currently not understood.