1. Ear Structure & Function
12-13 January 2014

2. Anatomy of the Ear External Ear Structures: Pinna auditory canal
ear drum
Function:
Funnel and conduct sound to middle ear

3. Anatomy of the Ear Middle Ear Structures: Ossicles Malleus Incus
Stapes
Eustacian / auditory tube
Function:
Amplify and conduct sound to inner ear

4. Anatomy of the Ear Inner Ear Structures: Osseous labyrinth
Semicircular canals
Vestibule
cochlea
Function:
Receive sound and equilibrium stimuli

5. Anatomy of the Ear
NOTE: Diagrams are misleading. The entire inner is bony, except for the labyrinth which is a series of cavities (spaces) within the bone.

6. Outer (External) Ear
Function:

7. Outer (External) Ear
Function: to funnel and conduct sound to the middle ear
Pinna collect sound waves and direct to the tympanic membranes … but in humans, not very effectively.
Cerumen (ear wax) lines the external auditory canal.
Antibacterial
Also discourages bugs, mold, etc.
Lubricates ears
Helps trap / remove foreign particles
The tympanic membrane (ear drum)
vibrates when sound waves hit it,
transmitting the sound to the
middle ear
A reflex tightens the ear drum in response to loud, low-pitched sounds – this reduces the sound transmitted to the ear and protectes our hearing

8. Disorders of the Outer Ear
Ear Wax Blockage
Ear wax can become impacted, usually from hearing aid use or inappropriate methods of cleaning the ears
Can cause temporary loss of hearing

9. Disorders of the Outer Ear
Otitis Externa (Swimmer’s Ear)
Infection of external auditory ear canal, usually due to excess moisture in the ear canal (such as from swimming), though cuts and scrapes to the ear canal can also become infected.
In addition
Picture through an otoscope. Notice that the canal is red but the ear drum is clear and not bulging.

10. Middle Ear
Function:
In addition

11. Middle Ear
Function: to AMPLIFY the sound and conduct it to the oval window of the inner ear. How? The tympanic membrane transmits sound to the three ossicles. The ossicles act like levers, amplifying the sound and transmitting it to the oval window, a membrane-covered opening to the inner ear.
In addition

12. Eustachian Tubes Structure
Tube that connects the middle ear to the nose and throat
Mostly closed, but opens when we move our jaw
Why do we have it?
Equalize pressure in the middle ear
Drain fluids to the throat
This is why its helpful to yawn or chew gum on a plane ride
Remember: the tympanic membrane seals the middle ear from the outer ear – so the only way for air / fluids to leave the middle ear is through the eustachian tubes
In addition

13. Disorders of the Middle Ear
Otitis media (middle ear inflammation / infection) –
Inflammation (often with the buildup of infected fluids) within the middle ear
Visible with an otoscope as a bulging eardrum
Usually caused from a respiratory infection
Babies who are allowed to drink bottles while lying down are also very likely to get ear infections
Much more common in young children, because their Eustachian tubes are narrower and more horizontal
In addition

14. Disorders of the Middle Ear
myringotomy–
Ear tubes are often recommended for children who experience chronic middle ear infections or fluid build-up
The tube is placed in the ear drum, but performs the functions of a eustachian tube – ventilating and draining the middle ear.
In addition

15. Hearing & the Inner Ear
Hearing takes place within the cochlea of the inner ear.
Cochlea is a long, curled cavity with three layers
2 layers of perilymph – a plasma-like fluid
In-between: a system of membranes that contain the organ of Corti and the mechanoreceptors (hair cells) that create the nerve impulse
In addition

16. Hearing & the Inner Ear
The top diagram is a cross-section of the cochlear cavity.
Take a moment to figure out …
What fills the scala vestibuli?
The scala tympani?
The cochlear duct?
In addition

17. Hearing & the Inner Ear
When the stapes beats against the oval window, it causes pressure waves within the perilymph
The movement of the perilymph disturbs the cilia (receptors) of the Organ of Corti, generating a nerve impulse
Different frequencies (pitch) vibrate the membrane in different locations.
High pitches are heard that the front, low at the back.
In addition

18. Hearing & the Inner Ear
When the stapes beats against the oval window, it causes pressure waves within the perilymph
The movement of the perilymph disturbs the cilia (receptors) of the Organ of Corti, generating a nerve impulse
The round window is a membrane-covered opening just below the oval window. It bulges to keep the pressure waves from bouncing back.
In addition
Watch me!
Just for fun!

19. Closure What were our objectives, and what did you learn about them?
What was our learner profile trait and how did we exemplify it?
How does what we did today address our unit question?