Ossicular connections Malleus: Manubrium of malleus connects to umbo of TM. Incus: Head of malleus connects to body of incus (incudo-mallear joint) Stapes: Inferior process of incus connects to form lenticular process, which connects to the stapes (incudo-stapedial joint) Footplate of the stapes connects to the oval window

Ossicular connections, cont’d. Suspended in the middle ear cavity by axial ligaments Posterior ligaments of incus Anterior ligaments of malleus Middle ear muscles Tensor tympani: Connected to manubrium of the malleus Activated by the trigeminal nerve Stapedial muscle: Connected to the head of the stapes Activated by the facial nerve

Functions of the middle ear Effective sound transmission to inner ear Shields the round window from direct air pressure variations Protective function: Acoustic reflex http://www.neurophys.wisc.edu/animations/

Possible methods of sound transmission into inner ear Bone conduction: Through bones of the skull Air in the middle ear cavity Through the ossicles: Most effective

Nature of middle ear cavity Not a completely closed cavity Necessary for efficient ossicular chain movement Opening through the eustachian tube Pressure equalization