Overview of the Ear, and Anatomy & Physiology of the Outer Ear

Flashcards to review the anatomy and physiology of the ear, focusing on the outer ear and sound localization principles.

What are the three major parts of the ear?

Outer ear, middle ear, and inner ear.

What is the primary function of the outer ear and middle ear?

To collect and transmit sounds.

What is the primary function of the inner ear?

It contains vestibulocochlear organs, converts sound and body movements into neural impulses, and is responsible for sound perception and balance maintenance.

Describe the simplified pathway of sound waves through the ear to the brain.

Sound waves propagating in air
Mechanical
Fluid waves
Neural signals.

What are the main functions of the outer ear and middle ear in acoustic energy processing?

Receive acoustic energy, convert acoustic energy into mechanical energy, and deliver mechanical energy to the inner ear.

What does 'anterior' mean in anatomical terms?

Front side of the body.

What does 'posterior' mean in anatomical terms?

Back side of the body.

What does 'superior' mean in anatomical terms?

Higher position on the body.

What does 'inferior' mean in anatomical terms?

Lower position on the body.

What does 'lateral' mean in anatomical terms?

Toward the side of the body.

What does 'medial' mean in anatomical terms?

Toward the middle of the body.

What does 'proximal' mean in anatomical terms?

Toward the center of the body.

What does 'distal' mean in anatomical terms?

Farthest from the center of the body.

What two main parts compose the outer ear?

The pinna (auricle) and the external auditory meatus (canal).

Which structure separates the outer ear from the middle ear?

The tympanic membrane (eardrum).

What is the pinna (auricle) primarily made of?

Primarily cartilage covered with skin.

What is the function of the pinna?

To collect and funnel sound waves into the ear canal.

Which part of the pinna is the lowest portion, consisting of skin and fat with no cartilage?

The lobule.

What is the deepest, bowl-shaped depression in the pinna that leads directly into the opening of the ear canal?

The concha.

What is the approximate range of length for the external auditory meatus (canal)?

~2.5 cm to 3.5 cm long.

What structure marks the internal ending of the external auditory meatus?

The tympanic membrane (eardrum).

Which portion of the ear canal contains hairs and glands that create cerumen (ear wax)?

The cartilaginous portion (outer 1/3).

Which portion of the ear canal does not contain hairs or ceruminous glands and has a thinner layer of skin?

The osseous (bony) portion (inner 2/3).

What are the main physiological functions of the outer ear?

Sound transmission, sound amplification, sound direction and localization, and protection of the middle ear.

At what frequency is the pinna most effective as a sound collector?

Around ~5000 Hz.

How does the pinna contribute to sound localization?

Its surface ridges and depressions create complex resonance patterns that shift with the sound source, aiding in horizontal, vertical, and front/back discrimination.

How does the external auditory meatus (ear canal) contribute to sound amplification?

It acts as a quarter-wave resonator, boosting frequencies between 3,000–4,000 Hz by ~10–15 dB.

Which part of the outer ear is the main resonance cavity for sound amplification?

The ear canal.

What is 'sound localization'?

Locating a sound source in space.

What are the three dimensions referenced in sound localization?

Azimuth (horizontal plane), Elevation (vertical plane), and Distance.

What are the two main categories of localization cues?

Monaural (one ear) and Binaural (two ears).

What is the main role of monaural localization cues?

Localization in the vertical plane (elevation).

How does the pinna effect aid in monaural localization?

Sound waves reflected off the folds of the pinna cause changes in the sound's spectrum, which are interpreted by the central auditory nervous system as differences in the elevation of the sound source.

What are the two types of binaural localization cues?

Interaural Level Difference (ILD) and Interaural Time Difference (ITD).

What is the 'head shadow effect'?

The attenuation (reduction) of sound intensity at the ear farthest from the sound source due to obstruction by the head.

Is the head shadow effect more prominent for high or low frequencies?

High frequencies (short wavelength).

What is Interaural Level Difference (ILD)?

Differences in intensity level between the ears.

Interaural Level Difference (ILD) is strongest at what type of frequencies?

High frequencies (>1500 Hz).

If a sound arrives from the left side, how does its loudness compare between the left and right ears, according to ILD?

It is more intense (louder) in the left (nearer) ear than the right (farther) ear.

What is Interaural Time Difference (ITD)?

Differences in timing between the ears.

Interaural Time Difference (ITD) works best for what type of frequencies?

Low frequencies (<1500 Hz).

ILD is strongest at frequencies, while ITD is strongest at frequencies.

High; low.

When we combine ILD and ITD, what does our brain achieve?

Robust cues for azimuth (horizontal localization) estimation.

How does the external ear provide protection to the eardrum and middle ear?

Its small ear canal opening, narrow passage, hairs, and cerumen (earwax) trap dust and small particles, and it has a self-cleaning mechanism.