2014 Basic Science

Question 1

Question 9
Abnormal development of which structure leads to altered orientation of the upper limb in mirror hand?
1. Sclerotome
2. Resting zone
3. Progress zone
4. Apical ectodermal ridge
5. Zone of polarizing activity

Answer 1

5. Zone of polarizing activity
6. Sclerotome: one of the paired masses of mesenchymal tissue, separated from the ventromedial part of a somite, which develop into vertebrae and ribs.
7. Resting zone: this is a zone of endochondral bone formation
8. Progress zone: layer of mesodermal cells immediately beneath the apical ectodermal ridge in the developing limb bud
9. AER: at the distal tip of the limb bud, interacts with progress zone to grow limb. Ectodermal cells
10. Zone of polarizing activity: posteriorly-placed on the limb bud. Mesodermal cells that direct the AP-axis of limb growth