Anatomy Physiology and Disorders of the Hearing

Major Divisions of the Ear

Peripheral Mechanism Central Mechanism

Outer Ear

Middle Ear

Inner Ear

VIII Cranial Nerve

Brain

Question

What is the purpose of the pinna?

A. Cosmetics

B. Sound collector

C. Same side localization

D. A and B

E. B and C

Outer/External Ear

• Auricle=Pinna

• Cerumen=Wax

• External Auditory Meatus= Hole in temporal bone (leads to Auditory canal)

• Tympanic Membrane-ear drum

Pinna

External Auditory Meatus

Pinna

Question

Another name for pinna?

A. External auditory meatus

B. External auditory canal

C. Ear lobe

D. Auricle

E. None of the above

Function of Outer Ear

• Collect sound• Localization• Resonator• Protection• Sensitive

(earlobe)• Other?

Pinna

• localizes• Directs sound into the ear• Each individual's pinna

creates a distinctive imprint on the acoustic wave traveling into the auditory canal

Question

Cerumen should be routinely removed from the ear canal?

A. True

B. False

Cerumen• Repel water

• Trap dust, sand particles, micro-organisms, and other debris

• Moisturize epithelium in ear canal

• Odor discourages insects

• Antibiotic, antiviral, antifungal properties

– Cleanse ear canal

Tympanic Membrane

• Separates outer from the middle ear

• Protective barrier to the middle ear

• Cone-shaped (depressed inward)• 1st to vibrate in response to sound

waves.

External Ear Care

Hazardous to health:

• Ear candling

• Swabs

• Foreign objects

Outer Ear Hearing Disorders

• Outer ear• CHARGE• Down Syndrome

– Ears small and low set

• Fetal Alcohol Syndrome– Deformed ears

Grow Ear?

• Size and shape

The big picture

What is sound?

• Sound is a form of energy that can be heard and travels in waves.

• When matter vibrates or moves back and forth very quickly, a sound is made.

• Sound waves can travel through solids, liquids, or gases.

•

Sound makes the air vibrate.

• For sound to be heard, sound vibrations must have air or some other kind of matter to travel through.

• Can’t hear sound in outer space because there is no air or other matter to carry sound vibrations.

Middle Ear

The function of the middle ear is to?

A. Cause middle ear infections in young children

B.Amplify sounds

C.Interpret sounds

D.Analyze sounds

E.None of the above

Middle Ear

What are the parts of the middle ear?

A. Ossicles and cochlea

B. Ossicles and eustachian tube

C.Tympanic membrane and auricle

D.I don’t know

Middle Ear

OssiclesMiddle Ear Muscles

Eustachian TubeMastoid

Function of Middle Ear

• Conduction– Conduct sound from the outer ear to the inner ear

• Protection– Creates a barrier

• Transducer– Converts sound waves to mechanical energy

• Amplifier

Middle Ear (parts)

• Auditory Ossicles - malleus, incus, stapes - transmit vibrations and amplify the signal

• Eustachian tube- connects the middle ear to the throat - helps maintain air pressure

Eustachian Tube

• Connects the middle ear with the nasopharynx

• Opens during swallowing and yawning

• This equalizes the pressure on either side of the eardrum

• Necessary for optimal hearing.– Without this function the eardrum could

prolapse. – Plugged ears on a plane

The Eustachian tube:

A. Opens when one yawns

B. Opens when one smiles

C. Opens when one blinks

D. It is always open

E. Never opens

Ossicles

• Malleus (hammer)

• Incus (anvil)• Stapes

(stirrup) smallest bone of the body

Middle Ear Disorders

• Middle Ear disorders– Acute otitis media– TM Perforation

Question

The function of the inner ear:

A.Balance

B.Hearing

C.Touch

D.All the above

E.A and B

Inner Ear = Labyrinth

• Labyrinth series of fluid filled tubes responsible for

equillibrium (balance) and hearing.• Made of 2 main regions: Semicircular canals &

Cochlea• Semicircular Canals - sense of equilibrium

• Cochlea – senses hearing

• Organ of Corti - contains hearing receptors, hair cells

detect vibrations

Organ of Corti

Inner Ear: Cochlea

• Inside the cochlea are special neurons called HAIR CELLS

• The stapes is attached to the OVAL WINDOW, and vibrations cause the fluid in the inner ear to vibrate

• This moves the hair cells, transmitting the vibration.

• Therefore the HAIR CELLS in this region are

receptors for HEARING.

Sense of Equilibrium

• Static Equilibrium - sense the position of the head, maintain stability and posture

• Dynamic Equilibrium (semicircular canals) - balance the head during sudden movement

• Cerebellum (brain)- interprets impulses from the semicircular canals and maintains overall balance and stability

Steps in Hearing

1. Sound waves enter external auditory meatus

2. Eardrum vibrates

3. Auditory ossicles (malleus, incus, stapes) amplify vibrations

4. Stapes hits oval window and transmits vibrations to cochlea

5. Organs of corti contain receptor cells (hair cells) that deform

from vibrations

6. Impulses sent to the vestibulocochlear nerve

7. Auditory cortex of the temporal lobe interprets sensory

impulses

8. Round window dissipates vibrations within the cochlea