Osseous meatus is recognized by its non-hair bearing epithelium which extends medially up to the annulus of the eardrum.
Bilateral anterior bony hump with retracted eardrum of a patient. Note the inferior meatal recess (arrow) where small foreign body may lodged and
potentially missed on conventional otoscopic examination.
Antero-inferior recess (arrow). Close-up view (ellipse)
The osseous auditory meatus is clinically identified as non-hair bearing epithelium and blends with the eardrum edges. The inner 2/3rd of the ear canal length is bony and the outer 1/3rd is cartilaginous. The epithelium of bony meatus is highly sensitive to painful stimuli and manipulation may trigger cough reflex.
Another example of antero-inferior recess (arrow) of the left ear canal. The eardrum is also retracted with small rim of tympanosclerosis seen posteriorly.
Isthmus is the natural narrowing of the ear canal. It is located at two region: at junction between the cartilaginous-bony junction and just before the anterior meatal recess (dots).