Answer to Question #173396 in Zoology for Edwin L.

Question

Enumerate the components of the Pharyngeal Apparatus (Clefts, Arches, and Pouches) and their derivatives. 

Answer 1

The development of the head and neck begins in the 4th and 5th week. Growth of mesenchymal tissue (connective tissue) in the cranial region of the embryo results in the formation of arches, separated by clefts. These are the pharyngeal arches and pharyngeal clefts.

Simultaneously, a number of outpocketing appear on the lateral wall of the pharynx – the pharyngeal pouches. The pouches separate the arches on the internal (endodermal) surface whilst the clefts separate the arches on the external (ectodermal) surface.