Ii

Malleus Stapes I

- Cochlear nerve

Cochlea

Eustachian tube

Tympanic membrane

Mastoid process

Bone

Middle ear cavity

The ear canal opens behind the tragus and curves inward about 24 mm. Its outer portion is surrounded by cartilage. The skin in this outer portion is hairy and contains glands that produce cerumen (wax). The inner portion of the canal is surrounded by bone and lined by thin, hairless skin. Pressure on this latter area causes pain—a point to remember when you examine the ear.

The bone behind and below the ear canal is the mastoid part of the temporal bone. The lowest portion of this bone, the mastoid process, is palpable behind the lobule.

At the end of the ear canal lies the tympanic membrane (eardrum), marking the lateral limits of the middle ear. The middle ear is an air-filled cavity that transmits sound by way of three tiny bones, the ossicles. It is connected by the eustachian tube to the nasopharynx.

The eardrum is an oblique membrane held inward at its center by one of the ossicles, the malleus. Find the handle and the short process of the malleus—the two chief landmarks. From the umbo, where the eardrum meets the tip of the malleus, a light reflection called the cone of light fans downward and anteriorly. Above the short process lies a small portion of the eardrum called the pars flaccida. The remainder of the drum is the pars tensa. Anterior and posterior malleolar folds, which extend obliquely upward from the short process, separate the pars flaccida from the pars tensa but are usually invisible unless the eardrum is retracted. A second ossicle, the incus, can sometimes be seen through the drum.

Stapes Pars Tensa

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