pharyngeal pouches

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pha·ryn·ge·al pouch·es

paired evaginations of embryonic pharyngeal endoderm, between the pharyngeal arches, extending toward the corresponding ectodermally lined pharyngeal grooves; during development they evolve into epithelial tissues and organs, such as thymus and thyroid glands.

pharyngeal pouches, the four pairs of evaginations from the lateral walls lining the pharynx between the branchial arches in a developing embryo.
References in periodicals archive ?
Older theories hold that they are congenital abnormalities caused by an incomplete obliteration of pharyngeal pouches.
2) The thymus is derived from the third and fourth pharyngeal pouches.
When they do occur, they typically arise from the parotid gland and the first and second pharyngeal pouches.