Pharyngeal Apparatus: Clefts

Question 1

1st cleft

Answer 1

Forms external auditory meatus and ear drum outer layer

Question 2

2nd, 3rd, 4th clefts

Answer 2

1. Active proliferation of 2nd arch mesodermal tissue leads to downwards growth to overlap 3rd and 4th arches and related clefts
2. Finally, it merges with epicardial ridge in neck
3. 2nd arch is separated from 2nd, 3rd, and 4th clefts by cervical sinus which will be completely obliterated leaving no remnant