Middle Ear

Tympanic Cavity

• In petrous portion of temporal bone.
• Narrow and oblique.
• Tympanic cavity is directly internal to tympanic membrane.
• Epitympanic recess is space superior to tympanic membrane.
• Connected anteriorly to nasopharynx via the auditory tube.
• Connected posteriorly with mastoid air cells via mastoid antrum.
• Lined by mucous membrane.
• Contains:
• 3 bones: malleus, incus, and stapes
• 2 muscles: tensor tympani, and stapedius
• 2 nerves: chorda tympani, and tympanic plexus.

Ossicles

Malleus

• Head lies in epitympanic recess.
• Articulates with incus
• Handle attached to TM.
• Chorda tympani nerve crosses medial surface of neck.

Incus

• Lies in epitympanic recess.
• Head articulates with head of malleus.
• Long process articulates with stapes.
• Short process connected by ligament to posterior wall.

Stapes

• Base fits into fenestra vestibuli (oval window).
• Head articulates with incus.

Overview of the Middle Ear

Articulation of the ossicles

These bones form a chain across the tympanic cavity from the TM to fenestra vestibuli (oval window). Covered by mucous membrane that also lines the tympanic cavity. Transmits vibration movements of the TM to the inner ear. Functions to increase the force but decrease the amplitude.

White: tympanic membrane and annular ligament, and posterior incudal ligament Red: stapedius muscle and tensor tympani

Nerves in the middle ear

White: tympanic membrane and ligaments Cream: malleus, incus, stapes Red: stapedius muscle and tensor tympani Blue: inner ear Yellow: nerves

Schematic view of the middle-ear cavity

Middle ear (tympanic cavity)

Lateral wall (the tympanic membrane) has been removed to see the interior of the middle ear. RED: Internal carotid BLUE: Internal jugular vein PURPLE: Tensor tympani YELLOW: Facial nerve(VII) with nerve to stapedius & chorda tympani DARK GREEN: Auditory tube, oval and round windows LIGHT GREEN: Cochlea