The development of the ear.

ABSTRACT

The ear consists of three parts which are of different origin but function as one unit. The internal car originate from the otic vesicle, which in the fourth week of development splits off from the surface ectoderm. This otic vesicle divides in a ventral component which give rise to the saccule and cochlear duct, and a dorsal component which gives rise to the utricle, semicircular ducts and endolymphatic duct. The epithelial structures so formed are known as the membranous labyrinth. The middle ear, consisting of the tympanic cavity and auditory tube, is lined with epithelium of ectodermal origin of the first pharyngeal pouch. The ear icicles, the malleus and incurs are derived from the first and the stapes from the second pharyngeal arches. The external auditory meatus develops from the first pharyngeal cleft and is lined at the bottom by the tympanic membrane. In order to understand ear development, pig and chick embryos are used in laboratory studies. However, since pig embryos are not easily available, this study compares the ear development of pig and rat embryos. The study indicates that the ear of the pig and rat develop in the same manner and rat embryos could be used in the future instead of pig embryos for studying ear development.