Deck 10: Limb Development

Question 1

The apical ectodermal ridge forms at the boundary between regions expressing ________________.

A)Wnt-7a and En-1
B)Shh and Msx-1
C)Wnt-7a and Shh
D)En-1 and Msx-1
E)Wnt-7a and Msx-1

Answer 1

A

Question 2

The skeletal musculature of the limb arises from the _________________.

A)Somatopleure of the lateral plate mesoderm
B)Neural crest
C)Splanchnopleure of the lateral plate mesoderm
D)Neural tube
E)Somites

Answer 2

E

Question 3

In the developing limb,the sonic hedgehog gene product is produced in the ______________.

A)Zone of polarizing activity
B)Region of interdigital cell death
C)Common muscle mass
D)Apical ectodermal ridge
E)Progress zone

Answer 3

A

Question 4

A mutation of Hoxa-13 is characterized by ______________.

A)Diplopia
B)Shortened phalanges
C)Syndactyly
D)Triphalangeal thumb
E)Amelia

Question 5

If the neighboring somites are removed,what would be missing from the developing limb?

A)Cartilage
B)Skeletal muscle
C)Bone
D)Digits
E)Melanocytes

Question 6

Which of the following associations of tissues contributing to the limb is incorrect?

A)Somite - myoblasts
B)Neural crest - pigment cells
C)Neural tube - motor axons
D)Splanchnopleure of the lateral plate - skeleton
E)Neural crest - sensory axons and Schwann cells

Question 7

Which anomaly is due to the absence of programmed cell death?

A)Triphalangeal thumb
B)Phocomelia
C)Polydactyly
D)Syndactyly
E)Diplopodia

Question 8

The connective tissue of the limb arises from ______________.

A)Paraxial mesoderm
B)Intermediate mesoderm
C)Somatic mesoderm
D)Lateral mesoderm
E)Neural crest

Question 9

Which of the following limb defects can be predicted by observing an early limb bud possessing two apical ectodermal ridges?

A)Syndactyly
B)Radial hemimelia
C)Diplopodia
D)Phocomelia
E)None of the above

Question 10

What is a principal function of the apical ectodermal ridge?

A)Stimulating outgrowth of the limb bud
B)Setting up the anteroposterior axis of the limb bud
C)Determining the organ-specific characteristics of the ectodermal appendages of the limb
D)Determining the pattern of neural ingrowth in the limb
E)Attracting the subcutaneous plexus of capillaries

Question 11

Syndactyly is due to abnormal patterns of _______________.

A)Cell death
B)Hox gene expression
C)Sonic hedgehog signaling
D)Myoblast migration from the somites
E)Fibroblast growth factors-2, -4, and -8 signaling from the apical ectodermal ridge

Question 12

Myoblasts migrating away from the somite toward the limb buds express _____________.

A)Pax-3
B)Sonic hedgehog
C)Paraxis
D)All of the above
E)None of the above

Question 13

___________,produced by the apical ectodermal ridge,stimulates outgrowth of the limb bud.

A)Sonic hedgehog
B)Bone morphogenetic protein-7
C)Fibroblast growth factor-4
D)Wnt-7a
E)None of the above

Question 14

Which molecule is involved in fixation of the dorsoventral axis of the limb bud?

A)Sonic hedgehog
B)Wnt-7a
C)Fibroblast growth factor-2
D)Hoxd-13
E)Retinoic acid

Question 15

In the initiation of limb development,the expression and secretion of ____________ by local mesodermal cells stimulate the overlying ectoderm to secrete fibroblast growth factor-8.

A)Sonic hedgehog
B)Fibroblast growth factor-10
C)Bone morphogenetic protein-7
D)Msx-1
E)None of the above

Question 16

Syndactyly is due to a disturbance in what embryological mechanism?

A)Induction
B)Programmed cell death
C)Cell migration
D)Failure of tube formation
E)Failure to fuse

Question 17

Sonic hedgehog is a morphogenetically active protein secreted by the _____________.

A)Apical ectodermal ridge
B)Nonridge ectoderm
C)Zone of polarizing activity
D)Limb cartilage
E)Neural crest