MI: Ear Anatomy and Cochlear Implants

Sound

Mechanical energy that is transmitted by longitudinal pressure waves in a medium (such as water or air)

Pinna

collects sound waves and channels them into the ear canal

Auditory Canal

entry way for sound waves

Tympanic Membrane (Ear Drum)

a thin flap of skin that is stretched tight like a drum and vibrates when sound hits it

Malleus (Hammer), Incus (Anvil), and Stapes (Stirrup)

The ossicles: malleus connects to the tympanic membrane transferring auditory oscillations to the incus and then the stapes. The stapes connects to the oval window allowing for mechanical energy to be transferred to the fluid-filled inner ear.

Oval Window

connects ossicles to cochlea, leads to movement of fluid within the cochlea and activation of receptors for hearing

Round Window

vibrates in opposite phase to vibrations entering the inner ear through the oval window. In doing so, it allows fluid in the cochlea to move

Semicircular Canals (Vestibular Apparatus)

lined with hair cells and filled with fluid to maintain balance and equilibrium

Cochlea

Sound waves are transduced into electrical impulses that the brain can interpret as individual frequencies of sound

Auditory (8th Cranial) Nerve

neural impulses travel to temporal lobe

Tympanic (Middle Ear) Cavity

area surrounding the ossicles

Eustachian Tube

opens intermittently to equalize the intratympanic air pressure with the pressure in the external auditory canal

Cochlear Implant

An electrical prosthetic device that enables individuals with sensorineural hearing loss to recognize some sounds and that consists of an external microphone and speech processor that receive and convert sound waves into electrical signals which are transmitted to one or more electrodes implanted in the cochlea where they stimulate the auditory nerve

Microphone

captures sound

Processor

converts sound into digital signal

Transmitter

A transmitter sends sound signals to a receiver and stimulator implanted under the skin

Receiver

stimulate the auditory nerve with electrodes that have been placed in the cochlea

Electrodes

Conductor of electricity: takes the place of damaged cochlear structures or hai​r cell - nerve synapses

Outer Ear

The outer visible portion of the ear that collects and directs sound waves toward the tympanic membrane by way of a canal which extends inward through the temporal bone

Middle Ear

The intermediate portion of the ear containing a chain of three ossicles that extends from the tympanic membrane to the oval window and transmits vibrations to the inner ear

Inner Ear

The essential part of the vertebrate organ of hearing and equilibrium that includes the vestibule, the semicircular canals, and the cochlea

Sensorineural Hearing Loss

Hearing loss or impairment resulting from problems with the auditory nerves

Conductive Hearing Loss

sounds cannot get through the outer and middle ear