From Canvas (Ears Anatomy Vocabulary) - Unit 13: Eyes and Ears

Auditory

Pertaining to the sense of hearing.

Audiology

The field of study focused on hearing, sound perception, and hearing impairment.

Audiologist

A healthcare specialist who specializes in the study, assessment, and management of hearing and hearing disorders.

Otolaryngology

The medical specialty that studies the anatomy and physiology of the ears, nose, mouth, and throat (ENT) and uses diagnostic tests, medical and surgical procedures, and drugs to treat ENT diseases.

ENT System

The ears, nose, and throat system located entirely in the head and neck, where the head contains external and internal structures of the ears, nose, mouth, and sinuses, and the neck contains the pharynx and larynx.

Overview of the Ear

The ear is divided into three distinct anatomical sections (external ear, middle ear, and inner ear) and serves two primary functions: providing the sense of hearing and acting as the sensory organ for balance or equilibrium; having one ear on each side of the head provides binaural hearing (hearing from both sides).

Eighth Cranial Nerve

Also called the acoustic or auditory nerve, this cranial nerve carries electrical nerve impulses for both hearing and balance from the inner ear to the brain.

Auricle (Pinna)

The visible outer cartilaginous flap and earlobe portion of the external ear not contained within the head; it collects sound waves from the environment and directs them inward into the ear canal.

External Auditory Canal (Ear Canal)

The tube leading from the auricle to the middle ear; it is lined with tiny hairs (cilia) that help move sound waves inward and contains ceruminous sweat glands that secrete cerumen (earwax) to lubricate and protect the ear (though excess cerumen can block sound transmission).

Tympanic Membrane (Eardrum)

A thin, almost transparent membrane that separates the external ear from the middle ear and transmits sound vibrations to the ossicles; a rupture from trauma or infection causes pain and partial hearing loss, but typically heals spontaneously in about two weeks.

Ossicles

A group of three tiny bones in the middle ear (malleus, incus, and stapes) that mechanically transmit and amplify sound vibrations from the eardrum to the inner ear by up to 22 times their original force.

Malleus

The first auditory ossicle of the middle ear, shaped like a hammer, which connects directly to the tympanic membrane and transmits sound vibrations to the incus.

Incus

The second auditory ossicle of the middle ear, shaped like an anvil, which receives sound vibrations from the malleus and transmits them to the stapes.

Stapes

The third auditory ossicle of the middle ear, shaped like a tiny stirrup, which receives vibrations from the incus and connects to the oval window to transmit sound into the inner ear.

Eustachian Tube

A canal connecting the middle ear (tympanic cavity) to the pharynx (nasal throat) that opens during yawning or swallowing to equalize air pressure in the middle ear with atmospheric pressure, ensuring the eardrum vibrates maximally when struck by sound waves.

Oval Window

A membrane-covered opening that separates the middle ear from the inner ear, into which the base of the stapes fits to transmit physical vibrations into inner ear fluid waves.

Mastoid Process

A bony protrusion of the skull located directly behind the lower ear next to the jaw that anchors muscles and aids in hearing; due to its proximity to the middle ear, middle ear infections can spread to it and cause mastoiditis.

Inner Ear (Labyrinth)

A complex, fluid-filled network composed of a bony labyrinth housing a membranous labyrinth, containing three main structural areas: the vestibule, cochlea, and semicircular canals.

Vestibule

The central bony portion of the inner ear located next to the stapes between the cochlea and semicircular canals; it contains two membranous pouches (the utricle and saccule) filled with perilymph that aid in maintaining balance.

Utricle

A membranous pouch in the vestibule containing perilymph and specialized hair cell sensory receptors connected to the eighth cranial nerve, which respond to gravity and movement to maintain equilibrium.

Cochlea

A snail-shaped bony structure of the inner ear containing auditory fluids (endolymph and perilymph) that move to transmit sound vibrations to sensory receptors.

Organ of Corti

The true organ of hearing contained within the cochlea; it houses tiny hair cells stimulated by fluid vibrations that convert sound energy into electrical nerve impulses sent to the brain for sound interpretation.

Semicircular Canals

Three fluid-filled bony loops (superior, posterior, and inferior) situated at right angles to each other behind the vestibule; each canal has an enlarged base called an ampulla containing hair cell nerve endings that detect movement, where continued fluid motion can cause dizziness and motion sickness.

Process of Hearing

Sound waves are collected by the auricle, funneled through the external auditory canal, and strike the tympanic membrane, causing it to vibrate. These vibrations move the malleus, incus, and stapes, causing the stapes to push against the oval window. This fluid displacement sets up pressure waves within the perilymph and endolymph of the cochlea, which bend the sensory hair cells of the Organ of Corti. The hair cells convert these physical vibrations into electrical signals, which travel along the eighth cranial nerve to the cerebral cortex of the brain to be interpreted as sound.

Pediatric Life Span Considerations

At 36 weeks gestation fetal earlobes are soft, becoming firm by 40 weeks, while newborn ear canal walls remain pliable due to underdeveloped cartilage and bone. In infants and young children, the Eustachian tube is shorter and straighter than in adults, predisposing them to frequent middle ear infections that require careful clinical examination.

Geriatric Life Span Considerations

Aging causes the eardrum to thicken and middle ear bony joints to degenerate, while inner ear changes include atrophy of the cochlea, cochlear nerve cells, and the Organ of Corti. These degenerative changes lead to presbycusis (age-related hearing loss) and affect sound sensitivity, speech comprehension, and physical balance.