pharyngeal pouch

The pharyngeal pouch is an anatomical structure that develops in the early embryos of all vertebrates, including humans. These pouches are lateral expansions of the pharynx, which is the part of the endodermal gut located behind the mouth cavity.12

In aquatic vertebrates like fish, these pouches can form gill clefts used for respiration. In terrestrial vertebrates, including humans, the pharyngeal pouches contribute to the development of various structures. The first pair of pouches forms the auditory tubes and tympanic cavities. The second pair is associated with the formation of tonsils, while the third and fourth pairs give rise to the parathyroid glands. Additionally, parts of these pouches are utilized in the formation of the thymus and the rudiment of the thyroid gland. The aortic arches, crucial blood vessels, also develop between successive pharyngeal pouches.12