Anatomy and physiology of eustachian tube and middle ear related to otitis media.

The middle ear is part of a functional system composed of the nasopharynx and the eustachian tube (anteriorly) and the mastoid air cells (posteriorly). The only active muscle that opens the eustachian tube is the tensor veli palatini, which promotes ventilation of the middle ear. The eustachian tube also functions to protect the middle ear from excessive sound pressure, and nasopharyngeal secretions. The eustachian tube helps drain the middle ear during opening and closing by pumping secretions from the middle ear; clearance of secretions also occurs. An understanding of the anatomy and physiology of the system can aid the clinician in understanding the role of eustachian tube dysfunction in the cause and pathogenesis of middle ear disease and the possible contribution of allergy to this disease.