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DerivativesPharyngeal pouch Derivatives
1st pouch Eustachian tube,tympanic cavity
2nd pouch Palatine tonsil,tonsillar fossa
3rd pouch Inferior parathyroid,thymus glands
4th pouch Superior parathyroid
5th pouch Ultimobranchial body,parafollicular cells of thyroid
Pharyngeal clefts
• Outer ectodermal lined grooves • 4 in number• Only the first cleft remains and contributes to
facial structure• 1st cleft gives rise to external auditory meatus
and its epithelial lining gives rise to eardrum• Rest form the cervical sinus which soon
disappears
When it goes wrong
• Ectopic thymic and parathyroid tissue• Branchial cysts and fistulae• Neural crest craniofacial defects-Treacher-
Collins,DiGeorge,Robin sequence
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