ear

• Pathway of sound:

  1. Pinnae
  2. external auditory canal
  3. tympanic membrane
  4. ossicles
  5. oval window
  6. inner ear (organs of corti)
  7. auditory nerve or round window (excess sound)
• Pinna:

  channel sound waves

  made of cartilage so flexible

  higher the sound wave the higher the frequencies and the thicker the sound wave the louder the sound

  dogs can move to redirect sound waves
• Auditory canal:

  • conducts sound waves
  • has glands that secrete cerumen
• Cerumen functions:

  1. repels water
  2. moisture for epithelium
  3. traps dust, sand, dirt and other debris
  4. antibiotic and antifungal properties
  5. odour discourages insects
  6. cleanses ear canal
• Tympanic membrane:

  converts sound waves into mechanical waves by vibrating
• Ossicles (bones):

  • transmit and amplify waves, so sound is concentrated on a smaller area

  1. Malleus (hammer)
  2. Incus (anvil)
  3. Stapes (stirrup)
• Oval window:

  • passes vibrations from stapes to inner ear
• Eustachian Tube:

  • from wall of middle ear to nasopharynx
  • opens when yawning and swallowing:

  1. This equalizes pressure on the ear drum, without this different pressure between outside and middle of ear would cause the tympanic membrane to displace outwards
• Cochlear:

  organs of corti:

  convert pressure into nerve impulses
• Semi circular canals: Balance

  • Cristae in Ampulla - side to side
  • Maculae in Saccule and Utricles - up/down and tilt
• Round window:

  allows vibration to dissipate avoiding echoes