ears

• Ear


  Sense organ of hearing and equilibrium
• Ear


  • Consists of three distinct parts: the external ear, the middle ear, and the inner ear
• Tympanic membrane

  Separates the external ear from the middle ear
• External ear and tympanic membrane


  • Can be assessed by direct inspection and using an otoscope
• Middle and inner ear


  • Cannot be directly inspected, instead testing hearing acuity and the conduction of sound assesses these parts
• External ear


  • Composed of the auricle, or pinna, and the external auditory canal
• Auricle (pinna)

  Portion of the external ear visible without any tools, composed of a thin plate of yellow elastic cartilage covered by tight-fitting skin and shaped with hollows, furrows, and ridges that form an irregular funnel to conduct sound waves into the external auditory canal
• External auditory canal


  1. shaped in the adult, the outer part curves up and back, the inner part curves down and forward
• Cerumen


  Modified sweat glands in the external ear canal secrete a wax-like substance that keeps the tympanic membrane soft, has bacteriostatic properties, and serves as a defense against foreign bodies
• Middle ear


  A small, air-filled chamber in the temporal bone, separated from the external ear by the tympanic membrane and from the inner ear by a bony partition containing two openings, the round and oval windows
• Tympanic membrane (eardrum)


  A translucent, pearly gray partition stretched across the inner end of the auditory canal, separating it from the middle ear. It is concave and located at the end of the auditory canal in a tilted position such that the top of the membrane is closer to the auditory meatus than the bottom.
• Landmarks of the tympanic membrane


  • Handle and short process of the malleus
  • Umbo
  • Cone of light
  • Pars flaccida
  • Pars tensa
• 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
• Auditory ossicles in the middle ear

  • Malleus
  • Incus
  • Stapes
• Auditory ossicles


  Tiny bones responsible for transmitting sound waves from the eardrum to the inner ear through the oval window
• Eustachian tube


  Connects the middle ear to the nasopharynx, equalizing air pressure on both sides of the tympanic membrane
• Inner ear (labyrinth)

  Fluid-filled, made up of bony labyrinth and inner membranous labyrinth
• Parts of bony labyrinth

  • Cochlea
  • Vestibule
  • Semicircular canals
• Cochlear duct


  Contains the spiral organ of Corti, 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
• Hearing

  1. Sound vibrations traveling through air are collected by and funneled through the external ear

  2. Causing the eardrum to vibrate

  3. Sound waves are then transmitted through auditory ossicles as the vibration of the eardrum causes the malleus, the incus, and the stapes to vibrate

  4. As the stapes vibrates at the oval window, the sound waves are passed to the fluid in the inner ear

  5. The movement of this fluid stimulates the hair cells of the spiral organ of Corti and initiates the nerve impulses that travel to the brain by way of the acoustic nerve
• Conductive hearing


  Transmission of sound waves through the external and middle ear
• Perceptive or sensorineural hearing


  Transmission of sound waves in the inner ear
• Conductive hearing loss


  Related to a dysfunction of the external or middle ear (e.g., impacted earwax, otitis media, foreign object, perforated eardrum, drainage in the middle ear, or otosclerosis)
• Sensorineural hearing loss


  Related to dysfunction of the inner ear (i.e., organ of Corti, cranial nerve VIII, or temporal lobe of brain)
• Bone conduction (BC)


  Though less efficient, serves to augment the usual pathway of sound waves through air, bone, and, finally, fluid
• The Weber test. (A) For this test, which assesses sound conducted via bone, the tuning fork is placed at the center of the client’s head or forehead. (B) A normal result is when sound is heard equally in both ears. Conductive loss is indicated when sound lateralizes to the impaired ear. Sensorineural loss is indicated when sound lateralizes to the good ear
• The Rinne test


  1. Place tuning fork base on mastoid process

  2. When the client no longer hears the sound, move tuning fork to front of the external auditory canal

  3. Compare air and bone conduction (AC and BC, respectively) sounds
• Conductive loss


  • BC is heard longer or the same amount of time as AC (BC ≥ AC)
• Sensorineural loss


  • Client hears poorly in both ears, but AC is heard longer than BC (AC > BC)
• AC through the external or middle ear is impaired


  Vibrations through bone bypass the problem to reach the cochlea
• Inner ear or cochlear nerve is less able to transmit impulses


  Regardless of how the vibration
• POLYP Ear polyp: growth on inside the ear canal due to chronic ear infections or a skin cyst inside the ear (cholesteatoma). EXOSTOSIS Known as surfer’s ear, abnormal bone growth within the ear canal due to chronic irritation, heredity, or unknown reasons. MICROTIA Congenital abnormality where the external ear does not fully develop. TOPHI Hard external ear nodules associated with deposits of uric acid crystals in advanced gout.
• Acute otitis media


  Red, bulging membrane; decreased or absent light reflex
• Blue/dark red tympanic membrane

  Blood behind eardrum due to trauma
• Perforated tympanic membrane


  Perforation results from rupture caused by increased pressure, usually from untreated infection or trauma