Hearing and balance

Three layers of the ear

External, middle, inner

External acoustic meatus

Ear canal

Tympanic Membrane

Splits the external and middle ear

Tympanic cavity

Narrow air filled cavity in the temporal bone

Contents of the middle ear

Auditory ossicles, stapedius (CNVII) and tensor tympani muscles (CNV)

Pharyngotympanic tube

Connects middle ear to upper throat (pharynx)

Malleus

Attached to tympanic membrane

Parts of auditory ossicles (middle ear)

Malleus, incus, stapes

Incus

Connector between malleus and stapes

Stapes

Attached to oval window

parts of the inner ear

Bony labyrinth, membranous labyrinth

Bony labyrinth

Consists of cochlea, utricle, saccule, semicircular canals

Membranous labyrinth

k+ rich endolymph

Cochlea

Inner and outer hair cells

Inner hair cells

Tilts to cause opening of cation channels (+)

Outer hair cells

Efferent fibers, either help protect or increase responsiveness

Vestibular system

Saccule and utricle, ampulla

Saccule and utricle

Responds to the pull of gravity and changes in head position

Ampulla

Rotational movements of the head

Hearing transmission path

Tympanic membrane, ossicles, Scalia vestibuli (oval window), basilar membrane

Balance

Vestibular, visual, sensory systems, and VOR (vestibular-ocular reflex)