The Ear

Perry C. Hanavan

Outer Ear

• Peripheral– Outer ear– Middle ear– Inner ear– Auditory nerve

• Central– Brainstem– Midbrain– Cerebral

Peripheral

Outer Ear - Pinna

Middle Ear - Tympanum

Middle Ear – Tympanic Membrane

Middle Ear – Ossicles

Middle Ear - Ossicles

Middle Ear – Ossicles - Malleus

Middle Ear – Ossicles - Incus

Middle Ear – Ossicles - Stapes

Middle Ear

Inner Ear - Osseous

Inner Ear - Membranous

Inner Ear - Labyrinth

Inner Ear – Organ of Corti

Cochlear Structures

Inner Ear – Organ of Corti

Basilar Membrane

• Traveling wave

Inner Ear – OHC & IHC

• IHC– Non-motile– Afferent– Responds to

loud sounds• OHC

– Motile– Efferent– Responds to

soft sounds

OHCs

Two Theories of Motility

• Somatic prestin motor

• Hair bundle motor

Tip-links –Hair Bundle Motor

<<<IHC

OHC >>>

Tip Link Structure

• Tip Link Structure

Hair Bundle Motor

Tip-links

Auditory Nerve

2 Types of Auditory Neurons

Paul Fuchs YouTubePaul Fuchs YouTube

Type IType II

The wave V latency used in the standard ABR IT5 and I-V delay measures is dominated by neural activity from the high-frequency regions of the cochlea. Thus, unless the tumor affects these high-frequency fibers sufficiently, standard ABR latencies will be normal.

TUMOR

Large TumorAbnormal Standard ABR

Small TumorAbnormal Standard

ABR

Small TumorNormal Standard ABR

Standard ABR

HIGH-FREQUENCY

FIBERS

Facial Nerve Sup. Vest Nerve

Inf. Vest NerveAcoustic Nerve

Cross-section of Internal Auditory Canal