Ears

• The ear is the sense organ of hearing and equilibrium.
• The ear consists of three distinct parts: the external ear, the middle ear, and the inner ear.
• The tympanic membrane separates the external ear from the middle

  ear.
• external ear and the tympanic membrane can be assessed by direct

  inspection and using an otoscope.
• middle and inner ear cannot be directly inspected - testing hearing

  acuity and the conduction of sound assesses these parts of the ear.
• The external ear is composed of the Auricle or pinna, external

  auditory canal.
• The auricle (pinna) is the portion of the external ear visible without

  any tools - shaped with hollows, furrows, and ridges that form an

  irregular funnel to conduct sound waves into the external auditory

  canal.
• The external auditory canal is S-shaped in the adult.
• Modified sweat glands in the external ear canal secrete cerumen, a

  wax-like substance that keeps the tympanic membrane soft.
• Cerumen has bacteriostatic properties, and its sticky consistency

  serves as a defense against foreign bodies.
• What part of the ear can be asses by direct inspection and an otoscope?

  External ear and tympanic membrane
• 3 parts of the external ear

  pinna, external auditory canal, tympanic membrane
• The middle ear or Tympanic cavity, is a small, air-filled chamber in

  the temporal bone.
• The tympanic membrane has a translucent, pearly

  gray appearance and serves as a partition stretched across the

  inner end of the auditory canal, separating it from the middle

  ear.
• The tympanic membrane is concave and located at the end of the

  auditory canal in a tilted position
• Handle and short process of the malleus: the nearest auditory ossicle that can be seen through the translucent membrane
• Umbo: the base of the malleus, also serving as a center point landmark
• Cone of light: the reflection of the otoscope light seen as a cone due to the concave

  nature of the membrane
• Pars flaccida: the top portion of the membrane that appears to be less taut than the bottom portion
• Pars tensa: the bottom of the membrane that appears to be taut
• The middle ear contains three auditory ossicles: the malleus, the incus, and the stapes
• Air pressure is equalized on both sides of the tympanic membrane by means of the eustachian tube, which connects the middle ear to the nasopharynx
• The inner ear, or Labyrinth- is fluid-filled and made up of the bony labyrinth and an inner membranous labyrinth.
• The Bony labyrinth has three parts: cochlea, vestibule, and semicircular

  canals
• The inner cochlear duct contains the spiral organ of Corti, which is the

  sensory organ for hearing.
• Sensory receptors, located in the vestibule and the membranous

  semicircular canals, sense position and head movements to help maintain both static and dynamic equilibrium.
• The transmission of sound waves through the external and middle ear is referred to as conductive hearing
• The transmission of sound waves in the inner ear is referred to as perceptive or “sensorineural hearing.”
• a conductive hearing loss would be related to a dysfunction of the external or middle ear
• A sensorineural loss would be related to dysfunction of the inner ear
• Some ears have a Darwin tubercle, a clinically insignificant,

  small prominence on the auricle of the ear
• Earwax, produced by the apocrine glands in the external ear,

  varies between dry and wet wax based on genetics.
• Europeans and Africans tend to have wet earwax, and East

  Asians, Native Americans, and Eskimos tend to have dry earwax
• The same genetic variation leads to women with dry earwax

  having a lower incidence of breast cancer, seen especially in East

  Asian women.
• Presbycusis, a gradual sensorineural hearing loss, is common after the age of 50 years
• Tinnitus - ringing in the ear
• otitis externa is referred to as "swimmer's ear"
• Conductive hearing loss: Caused by something that stops sound

  getting through the outer or middle ear
• Sensorineural hearing loss (SNHL): Occurs when there is a problem in

  the way the inner ear or hearing nerve works
• Mixed hearing loss: Includes both a conductive and a sensorineural

  loss