EVERYDAY SCIENCE

Detailed explanation-1: -The resulting pouches give rise to the middle ear cavity, Eustachian tube, mastoid air cells, palatine tonsils, thymus, parathyroid, and parafollicular cells of the thyroid. [7] Each of these tissues develops from their respective pharyngeal pouch, or pouches, in the case of the parathyroid gland.

Detailed explanation-2: -Pharyngeal pouches develop in the early embryos of all vertebrates, including the air-breathing terrestrial reptiles, birds, and mammals. The number of pouches has been reduced in the course of evolution from six or more to four in tetrapods, and the posterior pouches may not actually break through.

Detailed explanation-3: -Pharyngeal pouches are endodermal out-pockets occurring between the pharyngeal arches in embryological development. Various transcription factors regulate the mechanical bending of the endodermal tube, resulting in pharyngeal pouch formation.

Detailed explanation-4: -The first amphibians evolved from a lobe-finned fish ancestor about 365 million years ago. The first reptiles evolved from an amphibian ancestor at least 300 million years ago. Mammals and birds both evolved from reptile-like ancestors. 03-Jul-2019