Embryology Weeks (outer and middle ear)

what occurs during the fourth week?

The pharyngeal arches are formed from different portions of the trilaminar. From this structure, many other structures begin to develop.

• the ossicles are begin forming from cartilage of the mesoderm

  • initially, the malleus and incus are attached, and later differentiate

• the external auditory meatus also begins to form from the first pharyngeal cleft

  • will continue to develop until after birth

• the auricle begins to develop at auricular hillocks on the first and second pharyngeal arches

what occurs during week five to eight?

the auricular hillocks will develop and move up to the final position of the ears on the lateral wall of the skull

what occurs during week 9

myoblasts from the arch mesenchyme proliferate at the region the stapedius and tensor tympani muscles will form

differentiation begins in week 9 once the structures are formed

what occurs during weeks 16 to 28?

arising from the first pharyngeal pouch, the eustachian tube connects the pharynx to the middle ear, and is continuous with the tympanic cavity

the tympanic cavity is formed from an expansion of the pharynx, and is also connected to the middle ear by the eustahian tube.