ACB 8120 Lecture Notes - Lecture 10: Eardrum, Eustachian Tube, Antihelix
12 Apr 2020
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Explain how the ear develops accounting for the multiple germ layers and pharyngeal arches involved. Internal ear develops as a vesicle from the surface ectoderm and migrates into the embryonic mesoderm. Middle ea r develops from pharyngeal pouch 1 (eustachian tube links middle ear to throat) The two recesses grow close together but separated by a thin membrane (tympanic membrane; which is a combination of all 3 germ layers) Describe the surface anatomy of the external ear in anatomical language. Helix large outer rim (has antihelix right underneath it) Tragus tab anterior to external auditory meatus (has antitragus inferior to it) External auditory meatus ( describes both the surface anatomic structure and the bony hole) Leads from auricle to tympanic membrane (through external auditory meatus) Starts cartilaginous, becomes bony as it enters the petrous part of temporal bone. The lateral surface of the tympanic membrane is also considered part of the external ear because of its embryologic origin.
