<s>[INST] context: (Dorsal part of the 1st ectodermal cleft) (357-IBS 8th) (317-I.B.Singh 8th)External acoustic meatus is derived from the dorsal part of the first ectodermal cleft. However, its deeper part is formed by proliferation of its lining epithelium.FATE OF ENDODERMAL POUCHESA. First pouch(a) Its ventral part is obliterated by formation of the tongue(b) Its dorsal part receives a contribution from the dorsal part of the second pouch, and these two together form a diverticulum that grows towards the region of the developing ear. This diverticulum that grows towards the region of the developing ear. This diverticulum is called the trubotympanic recess. The proximal part of this recess gives rise to the auditory (pharyngotympanic) tube, and the distal part to the, middle ear cavity including the tympanic antrumB. Second Pouch(a) The epithelial of the ventral part of this pouch contributes to the formation of the tonsil(b) The dorsal part takes part in the formation of the tubotympanic recessC. Third Pouch- give rise to inferior parathyroid gland & ThymusD. Fourth Pouch- gives origin to the superior parathyroid glands and may contribute to the Thyroid glandE. Fifth or Ultimobranchial pouch- give rise to ultimobranchial body (some species) & caudal pharyngeal complex [/INST] question: External acoustic meatus is derived from | options: A: Dorsal part of the first ectodermal cleft B: Ventral part of the first ectodermal cleft C: Dorsal part of the 2nd ectodermal cleft D: Ventral part of the 2nd ectodermal cleft | answer: A </s>