PHARYNGEAL II Flashcards
1
Q
P POUCHES are endoderm in origin and each pouch will develop a dorsal and ventral diverticle except for the 1st P pouch because
A
the tongue will form where the ventral diverticle would form
2
Q
1st P pouch
A
will form tubotympanic recess which will dilate at the distal end to form a primitive tympanic cavity and proximally will form an auditory tube. the lining of the primitive tympanic cavity will contribute to the formation of the eardrum/tympanic membrane
3
Q
2nd p pouch
A
- dorsal= later form the ear
2. ventral lining of the 2nd p pouch will differentiate and proliferate to form palatine tonsil
4
Q
3rd p pouch
A
- dorsal= will form the inferior parathyroid gland which will lose its attachment from the P gut and it will populate the migrating thyroid gland and the lower pole of the thyroid gland
- ventral lining will form the thymus, thymus will migrate in a chordal medial direction pulling the parathyroid with it, thymus will meet its counterpart from the right side and it will migrate into the thorax to attain its feutal position
5
Q
4th pouch
A
- dorsal= form superior parathyroid which will also lose connection to its P gut and populates the migrating thyroid gland superiorly
- ventral= unknown
6
Q
5th pouch
A
- rudimentary
- consists of an ultimobranchial body which does not contribute to an adult structure but it is a resting place for neural crest cells which will form cells of the particular thyroid gland
7
Q
P grooves
A
- 5th week
- there are 4 grooves
- only pouch of P arch 1 will form external acoustic meatus of the ear
- pouch of 2nd P arch expands in a chordal and lateral direction to fuse with the epicardial ridge in the lower neck regions, in the process it overlaps the P grooves of 2,3,4 arch and make them obliterate/smooth such that they will not have an adult structure
- 2nd groove will form cavity called cervical sinus which will disappear with further development
8
Q
brachial sinus and fistula
A
These appear when pharyngeal grooves 2, 3 and 4 persist
