Posts Tagged ‘middle ear anatomy’

Hearing is one of the five senses; it has a powerful role in the communication process. Hearing enables people to experience the world around them through sound. Remember the last conversation you had, the emotions and information exchanged, now imagine how that conversation would be like without the power of hearing. For many individuals suffering from a hearing loss is a reality.

Prevalence Of Hearing Loss:

  • Affects all ages;
  • 3 in 10 people over age 60 have hearing loss;
  • 65% of people with hearing loss are younger than 65;
  • 3 in 3,000 infants are born with severe to profound hearing loss;
  • At least 1.4 million children (18 or younger) have hearing problems;
  • The presence of hearing loss has doubled in the past 30 years


How We Hear:

The ear is made up of the inner, middle, and outer ear; and central auditory pathway. The process of hearing begins with the outer ear. The pinna or auricle collects sound energy and directs it down the ear canal into the eardrum. The incoming sound vibrations cause the eardrum to vibrate, setting into motion the malleus, incus, and stapes making up the ossicular chain of the middle ear. The stapes bone of the middle ear vibrates up against the oval window of the fluid filled inner ear. Fluids within the spiral shaped cochlea of the inner ear are set into motion, stimulating the hair cells of the Organ of Corti. When the hair cells respond, they activate neurons of the auditory nerve. The signal is now in the form of a neural code that can be processed by the nervous system.

Outer Ear Anatomy

  • Pinna
  • External Auditory Meatus (eardrum)
  • Tympanic Membrane

Middle Ear Anatomy

  • Tympanic Membrane
  • Ossicular Chain: Malleus Bone, Incus Bone, and Stapes Bone (smallest bones in the body)
  • Muscles: Tensor Tympani Muscle, Stapedius Muscle
  • Eustachian Tube

Inner Ear Anatomy

  • Cochlea
  • Inner and Outer Hair Cells

Center Auditory Pathways

  • 8th cranial nerve



Types of Hearing Loss:

Hearing loss is categorized by which part of the auditory system is damaged.

  • Three Basic Types:
  1. Conductive Hearing Loss: problem in the outer or middle ear
  2. Sensorinueral Hearing Loss: problem located in the inner ear or central auditory pathway
  3. Mixed Hearing Loss: refers to a conductive and sensorinueral hearing loss occurring at the same time
  • Causes:
  1. Conductive Hearing Loss: wax in the ear canal, a perforation the in the eardrum, or fluid in the middle ear
  2. Sensorinueral Hearing Loss: aging, infection or other disease, noise exposure, or related to a genetic disorder
  3. Mixed Hearing Loss


Degree Of Hearing Loss:

The degree of hearing loss refers to the severity of the loss.

  • Normal: -10 to 15 dB HL
  • Slight: 16 to 25 dB HL
  • Mild: 26 to 40 dB HL
  • Moderate: 41 to 55 dB HL
  • Moderately Severe: 56 to 70 dB HL
  • Severe: 71 to 90 dB HL
  • Profound: 91+ dB HL


The Audiometer and Test Environment:

The audiometer is the principle tool used in the process of evaluating a patient’s auditory functioning. It is an electronic device that produces and delivers sounds to the patient. It produces a audible threshold graph called an Audiogram that is interpreted by an audiologist when diagnosing a hearing disorder. To meet the need for an appropriately quiet environment, audiological testing is performed in specially constructed, sound-isolated rooms.


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