Medicine and Health related Information

The endodermal pouches take part in the formation of several important organs:-

1) FIRST POUCH:-

Its ventral part is obliterated by the formation of the tongue.
Its dorsal part receives a contribution from the dorsal part of second pouch and these together form a diverticulum that grows towards the region of developing ear. This diverticulum is called tubotympanic recess.
The proximal part of this recess gives rise to the auditory tube, the distal part of middle ear cavity including the tympanic antrum.

2) SECOND POUCH:-

a) The epithelium of the ventral part of the pouch contrivbutes to the formation of tonsil.
b) The dorsal part takes part in the formation of TUBOTYMPANIC RECESS.

3) THIRD POUCH:-

This gives rise to inferior parathyroid glands and thymus gland.

4) FOURTH POUCH:-

This gives origin to superior parathyroid gland and may contribute for the development of thyroid gland.

5) FIFTH or ULTIMO BRANCHIAL POUCH:-

A fifth pouch is seen for brief period during development. In some species it gives rise to ultimobranchial body. Its fate in man is controversial. It is generally believed to be incorporated into fourth pouch the together forming the caudal pharyngeal complex.
The superior parathyroid gland arises from this complex, the complex probably also gives origin to the parafollicular cells of thyroid.