Human Ear Anatomy: External, Middle, and Inner Structures

What is the function of the tympanic membrane?

It vibrates in response to sound waves, transmitting sound to the middle ear.

What are the three bones in the middle ear called?

Malleus, Incus, and Stapes.

What structure is responsible for balance in the inner ear?

The semicircular canals.

What is the role of the cochlea?

It converts sound vibrations into neural signals for hearing.

What is the function of the vestibulocochlear nerve?

It transmits sound and balance information from the inner ear to the brain.

What is the purpose of the auditory tube?

It equalizes pressure in the middle ear with the atmospheric pressure.

What are the two main divisions of the vestibulocochlear nerve?

Vestibular and cochlear divisions.

What is the significance of the oval window?

It is the membrane-covered opening that leads from the middle ear to the inner ear.

What is the function of the saccule and utricle?

They detect linear acceleration and head position relative to gravity (balance)

What is the role of the round window?

It allows for the displacement of fluid in the cochlea, facilitating sound transmission.

What is the anatomical term for the outer ear?

Auricle or pinna

What is the function of the cristae within the ampullae?

They detect rotational movements of the head.

perilymph make-up and function

-High in sodium (Na⁺) and low in potassium (K⁺)

-transmits mechanical sound vibrations from the middle ear

endolymph make-up and function

-High in potassium (K⁺) and very low in sodium (Na⁺)

-helps the hair cells detect the vibration/movement

Deiter cells (Organ of Corti) Function

-support outer hair cells

-extend to fill space

recticular lamina

Boundary that separates the endolymph and perilymph

Outer ear has _______ energy.

Acoustic

Middle ear has _____ energy.

Mechanical

Inner ear has ______ energy.

Hydro-machanical

Acoustic energy

Sound energy traveling through air (Sound waves travel through the air → eardrum)

Mechanical energy

Physical movement of solid structures (Eardrum → ossicles)

Hydro mechanical energy

Movement of fluid caused by mechanical energy (Stapes → cochlear fluid → basilar membrane)

Are Liquids compressible or NOT compressible?

Not compressible

Why is it important that liquids are NOT compressible?

because when the stapes pushes on the oval window, the fluid can't simply compress—it has to move, creating pressure waves inside the cochlea.

How is the cochlea organized?

Tonotopically organized

Define Tonotopically organized

-different frequencies are processed at different location

How is the cochlea Tonotopically organized?

• Base of cochlea → high frequencies (high pitch)

• Apex of cochlea → low frequencies (low pitch)

Why is it important that the cochlea is tonotopically organized?

so that different places respond best to different sound frequencies

Explain air to fluid impedance mismatch

Air and fluid resist sound differently, so much energy reflects. The middle ear increases pressure to transfer sound into fluid.

What does impedance mean?

how much something resists the movement of sound energy

Most basic flow of hearing

Acoustic → Mechanical → Hydromechanical → Transduction → electrical signal sent to brain

Which of the following correctly includes all the afferent auditory

brainstem nuclei in the correct order beginning from the most inferior to

the most superior?

CN, SOC, LL, IC, MGB

Function of Reissner’s membrane

Separates the scala vestibuli (perilymph) from the scala media (endolymph) and helps maintain their different fluid compositions

Theoretical loss of air in fluid

30 dB

At what Hz does the ear canal resonate the best?

3430 Hz

How does the pinna amplify sound?

It collects/funnels sound and boosts mainly 2–5 kHz frequencies.

How does the ear canal amplify sound?

It acts as a resonator, boosting frequencies around 2.5–3 kHz. (10-15 dB)

How does the middle ear give back loudness?

1. Area difference (tympanic membrane is much larger than the stapes' footplate)

2. Ossicular lever action (The malleus and incus act like a lever.)

3. Buckling/curvature of the tympanic membrane

   (The shape and movement of the eardrum help concentrate force toward the ossicles.)

The eustachian tube can best be described as:

normally closed and opens by the tensor veli palatini muscle

Main difference between baby and adult ear canal

Infant is more horizontal- causing ear infections, adult is more angled-allowing fluid to drain easier

Why is ear wax important?

-keeps ears clean

-q tips push wax into bony part, better to run water to them