Parts of the Ear and Energy Types

Outer Ear

Composed of:

• Pinna: collects sound like a funnel and directs down ear canal

• External ear (canal): transmits sound from pinna to middle ear, produces cerumen which serves as protective function

• Tympanic Membrane (ear drum): where outer ear ends, efficient vibrator to convert acoustic energy to mechanical energy

Middle ear

• Air filled space in temporal bone, starts back side of tympanic membrane, conducts mechanical energy to inner ear

Composed of:

• Auditory Ossicles (Ossicular Chain)

• Eustachian Tube (equalizes pressure, runs from middle ear to back of throat, normally closed, opens when yawning/swallowing, adults angle downward, childrens are horizontal and remain open- not as easily drained

• Pressure Equalization (PE) Tubes: surgically implanted to ventilate middle ear cavity

• TM Perorations: Ear Drum is easily perforated with small objects such as Q tips

Inner Ear:

• Two separate systems, same fluid running through both 

  • Semicircular canals: important for balance, movement, determining body position in space- not involved in hearing. 

  • Cochlea: bony tube curled like snail shell, divided into three tubes by two membranes- all three full of fluid, 

  • Organ of corti: located in cochlea, most important structure for hearing, thousands of hair cells that are bent (shearing action)- fluid above and below cause it to vibrate back and forth, creates neural impulses carried to brain by acoustic nerve 

• Function: since inner ear is filled with fluid, as stapes move in and out of oval window, water is displaced behind it. Action that converts mechanical energy into fluid energy

Energy Transfers

• outer ear: Acoustic energy (pressure waves) 

• Middle ear: mechanical energy (vibrations of ossicles 

• Inner ear: hydraulic energy (fluid waves) —> electrical energy (neural impulse) 

• From Inner Ear to Brain: electrical energy (neural impulse via auditory nerve)