Physiology of the Ear and Diving Barotrauma

Comprehensive practice questions covering the anatomy of the ear, the mechanism of hearing, and the physiological effects of pressure during diving.

What are the three main sections that comprise the ear?

The outer ear, middle ear, and inner ear.

What is the pinna and what is its primary function?

The pinna is the visible part of the ear composed of a thin piece of cartilage; its function is to funnel sound waves into the ear canal.

What structure marks the beginning of the middle ear at the end of the ear canal?

The eardrum or tympanic membrane.

What are the three tiny bones in the middle ear called collectively?

Ossicles.

Name the three ossicles and their corresponding common names.

The malleus (hammer), incus (anvil), and stapes (stirrup).

How does sound change as it passes through the middle ear?

Sound waves cause the eardrum to move, which moves the ossicles, changing sound waves into mechanical vibrations.

What is the entrance to the inner ear hit by the stapes?

The oval window.

Describe the structure and contents of the cochlea.

A snail-shaped bony structure filled with two fluids, perilymph and endolymph.

What is the Organ of Corti?

The sensory receptor in the cochlea that holds the hair cells, which are the nerve receptors for hearing.

Which nerve is responsible for transmitting sensory information from the semicircular canals to the brain?

The vestibular nerve.

What is the function of the auditory/cochlea nerve?

It carries nerve impulses from the cochlea to the brain.

How do hair cells in the cochlea respond to different sounds?

Individual hair cells respond to specific sound frequencies or pitches; only certain cells are stimulated depending on the pitch.

What is barotrauma in diving?

Damage caused by pressure changes, specifically occurring in the air-filled spaces of the body like the middle ear.

What structure connects the middle ear to the nasopharynx?

The Eustachian tube.

What pressure is present in the external auditory canal and middle ear at sea level?

$$1\,\text{atm}$$

Define 'Ear Squeeze' (Middle ear barotrauma) during descent.

A condition where outer ear pressure is greater than middle ear pressure, causing the eardrum to bulge inwards.

Define 'Reverse Block' during ascent.

A condition where middle ear pressure is greater than outer ear pressure, causing the eardrum to bulge outwards.

What is the Valsalva maneuver?

A forceful attempt to exhale against a pinched or blocked nose to equalize pressure.

Describe the Toynbee maneuver.

Pinching or blocking the nose and then swallowing.

How is the Frenzel maneuver performed?

Pinch the nose, close the back of the throat as if straining, and make the sound of the letter 'K'.

What should a diver do if equalization techniques are not working?

Ascend and try the techniques again, wriggle the jaw, yawn, swallow, or lengthen the neck, and do not continue descending.