Figure 242

Schematic drawings showing development of the ear. a. This drawing shows the relationship of the surface ectoderm-derived otic vesicle to the first pharyngeal arch during the fourth week of development. b. The otic vesicle sinks deep into the mesenchymal tissue and develops into the membranous labyrinth. Note the development of the tubotympanic recess lined by endoderm into the future middle-ear cavity and auditory tube. In addition, accumulation of mesenchyme from the first and second pharyngeal arches gives rise to tympanic ring tubotympanic recess incus malleus developing external acoustic meatus otic vesicle otic cartilaginous capsule stapes round window squamous part of petrous bone petrous part of temporal bone external acoustic meatus tympanic membrane

membranous labyrinth tympanic cavity auditory tube membranous labyrinth external acoustic meatus tympanic membrane tympanic cavity auditory tube squamous part of petrous bone petrous part of temporal bone

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