THE EAR

1
THE EAR
2
External Ear
3

• outer portion of the ear that is visible on the
  side of the head, called the pinna, skin and
  cartilage, with muscular attachments in the back.
  Its shape helps us localize where sounds in the
  environment are coming from.
• ear canal sounds coming from the front are more
  easily directed into the ear canal.
• tympanic membrane, also known as the ear drum.

4
(No Transcript)
5
Middle Ear
6

• The middle ear is that part of the ear between
  the external and the inner ear.
• Its outer border is the thin membrane known as
  the ear drum, or tympanic membrane. As sound
  strikes the ear drum, it vibrates and in turn
  transmits these vibrations to the three small
  bones of the middle ear
• the malleus
• the incus
• the stapes.
• The combination of the ear drum and the lever
  action of these bones helps to amplify the sound
  vibration.
• The end of the stapes is called the oval window
  and it is connected to the inner ear.

7

• The middle ear is normally filled with air.
• An opening called the eustachian tube connects
  the middle ear to the back of the upper throat.
  When this tube is opened, for example during
  yawning, the pressure in the middle ear is
  equalized to atmospheric pressure.

8
(No Transcript)
9
The Inner Ear
10

• The inner ear is the delicate structure which
  transforms the sound vibrations from the stapes
  into nerve signals that are transmitted to the
  brain. It also plays an important role in
  maintaining our balance. The inner ear consists
  of tiny fluid-filled canals encased in some of
  the hardest bone in the body.
• The hearing portion of the inner ear is the
  cochlea, a snail shaped structure that is
  connected to the stapes. As the stapes moves in
  and out, it produces fluid waves within the
  cochlea.
• These waves in turn cause movement of tiny cells
  within the cochlea called the hair cells. As
  these hair cells vibrate, they send signals to
  the brain which can then be interpreted as sound.

11
(No Transcript)
12

• The basic hearing test or audiogram tests one's
  ability to hear pure tones in each ear. A
  comparison between these two types of conduction
  can be very useful in localizing which part of
  the hearing mechanism is responsible for the
  loss.
• In particular, the test is useful in determining
  if the loss is due to problems with the portion
  of the middle ear that conducts sound from the
  ear canal to the middle ear (in which case it
  would be called a "conductive" hearing loss) or
  if it is due to the inner ear or the nerve that
  conducts the sound signals to the brain (in which
  case it would be called a "sensorineural" hearing
  loss).

13

• The results of audiograms are most often
  displayed in graph form. This graph shows the
  amount of hearing loss expressed in units called
  decibels at different sound frequencies (also
  called Hertz).
• High frequencies correspond to high tones, and
  low frequencies are low tones. Most audiograms go
  from around 250 hertz to 8000 hertz. A loss up to
  20 decibels on this graph is considered "normal".
  Hearing losses over 20 decibels are considered
  abnormal.

14
Cochlear Implant
15
What is a cochlear implant?

• The cochlear implant is a prosthetic replacement
  for the inner ear (cochlea) and is only
  appropriate for people who receive minimal or no
  benefit from a conventional hearing aid.
• The cochlear implant bypasses damaged parts of
  the inner ear and electronically stimulates the
  nerve of hearing. Part of the device is
  surgically implanted in the skull behind the ear
  and tiny wires are inserted into the cochlea. The
  other part of the device is external and has a
  microphone, a speech processor (that converts
  sound into electrical impulses), and connecting
  cables. It is battery powered, adjustable, and
  expensive.

16
(No Transcript)
17
(No Transcript)
18

• The Nucleus 22 Channel Cochlear Implant System is
  shown above.
• The various components are
• The electrode array (which is placed in the inner
  ear).
• The receiver for the electrode array.
• The speech processor, a small electronics package
  that typically is placed in the wearer's pocket.
• Transmitting coil and
• Microphone, both of which are worn behind the
  ear.

19
(No Transcript)
20

• Sounds in the environment are picked up by the
  small directional microphone.
• A thin cable (cord) sends the sound from the
  microphone to the Spectra 22 speech processor.
• The speech processor amplifies, filters and
  digitizes sound into coded signals.
• These coded signals are sent from the speech
  processor to the transmitting coil via the
  cables.
• The transmitting coil sends the signals across
  the skin to the implanted receiver/stimulator via
  an FM radio signal.
• The receiver/stimulator delivers the correct
  amount of electrical stimulation to the
  appropriate electrodes on the array.
• The electrodes along the array stimulate the
  remaining auditory nerve fibers in the cochlea.
• The resulting electrical sound information is
  sent through the auditory system to the brain for
  interpretation .

21
Diseases
22
Meniere's Disease
Meniere's disease first described in 1861 by the
French physician Prosper Meniere, is
characterized by multiple symptoms, all
associated with excessive fluid in the inner ear
involving both the hearing and balance organs.
Excessive fluid in the cochlea (hearing organ) is
known as cochlear hydrops. Excessive fluid in the
semicircular canals (balance organ) results in
dizziness and is known as vestibular hydrops.
Almost all Meniere's patients have both cochlear
and vestibular hydrops.
23
Earache (Otitis Media)
An earache or ear infection (otitis media) is
usually a complication of an upper respiratory
infection, such as a cold. Otitis media usually
occurs in children under 3 years of age. Symptoms
include inflammation of the middle ear, often
with fluid building up behind the ear drum. The
child may cry persistently, tug at the ear, have
a fever, be irritable, and be unable to hear
well. These symptoms may sometimes be accompanied
by diarrhea, nausea, and vomiting. Otitis media
is common in young children whether they attend
child care or are cared for at home. However,
some children appear to be more susceptible to
otitis media than other children.
24
Perforated Eardrums
A perforated eardrum is a hole or rupture in the
eardrum, a thin membrane which separates the ear
canal and the middle ear. The medical term for
the ear drum is the tympanic membrane. The middle
ear is connected to the nose by the eustachian
tube, which equalizes pressure in the middle ear.
A perforated eardrum is often accompanied by
decreased hearing and occasional discharge. Pain
is usually not present.
25
Tinnitus, or Head Noise
The presence of tinnitus, or head noise, is a
very common and annoying occurrence. It may be
intermittent or constant in character, mild or
severe in intensity, and vary from a low roar to
a high-pitched type of sound. It may be
subjective (audible only to the patient) or
objective (audible to others). It may or may not
be associated with hearing impairment.