Middle Ear Embryology
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The middle ear (tympanic) cavity is derived from the first pharyngeal pouch and the ossicles are from the first and second arch cartilages .
First Pharyngeal Pouch
- forms the auditory tube (narrow proximal part) & tympanic cavity (distal sac-like structure)
- tympanic membrane—forms from lining of tympanic cav.
- later comes into contact with epithelial lining of 1st pharyngeal cleft (future EAM)
Ossicles—(malleus, incus, & stapes) embedded in mesenchyme during most of development; in 8th month it degenerates & endoderm envelops them & connects them to wall of cavity
- malleus—1st pharyngeal arch (tensor tympanin = accompanying m. inn by CN V)
- incus—1st pharyngeal arch
- stapes—2nd pharyngeal arch (stapedius m = accompanying m. inn by CN VII)
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