Biology: The Ear - Audition and Balance Flashcards

This set of vocabulary flashcards covers the anatomical structures and physiological functions of the external, middle, and inner ear, including components of hearing and balance.

Pinna

Composed of cartilage and thick skin, its function is to collect and transmit sound waves to the middle ear.

Tympanic membrane

Also known as the eardrum, this thin connective tissue membrane serves as the boundary between the outer and middle ears and vibrates in response to sound.

Auditory canal (External acoustic meatus)

A short tube in the temporal bone approximately $2\,cm$ long that contains ceruminous glands and hairs to prevent foreign materials from entering the ear.

Auditory ossicles

The three small bones in the middle ear (malleus, incus, and stapes) that transmit vibrations from the tympanic membrane to the fluid in the cochlea of the inner ear.

Malleus

The auditory ossicle also known as the hammer.

Incus

The auditory ossicle also known as the anvil.

Stapes

The auditory ossicle also known as the stirrup; it is the smallest bone in the body and vibrates against the oval window.

Oval window

A membrane-covered opening that connects the middle ear to the scala vestibuli of the inner ear.

Round window

A membrane-covered opening that connects the middle ear to the scala tympani of the inner ear and bulges in response to pressure on the basilar membrane.

Mastoid antrum

A canal in the middle ear that leads into the air space of the temporal bone (mastoid process).

Pharyngotympanic (auditory) tube

A tube connecting the middle ear to the nasopharynx that equalizes pressure on both sides of the tympanic membrane.

Otitis media

An infection of the middle ear often caused by pathogens from a throat infection traveling up the pharyngotympanic tube.

Bony labyrinth

A series of channels running through the temporal bone filled with perilymph, which is similar to cerebrospinal fluid (CSF).

Membranous labyrinth

A series of membranous sacs within the bony labyrinth filled with endolymph, a potassium-rich intracellular fluid ($ICF$).

Perilymph

The fluid found within the bony labyrinth.

Endolymph

The potassium-rich fluid found within the membranous labyrinth.

Semicircular canals

Three canals oriented in three planes of space that house equilibrium receptors for detecting rotational movements.

Ampulla

The swollen end of each semicircular canal that houses the crista ampullaris.

Crista ampullaris

The sensory receptor for dynamic balance that responds to rotational movements of the head.

Ampullary cupula

A gelled matrix in the crista ampullaris where stereocilia of hair cells are embedded; it contains no otoliths.

Vestibule

The central egg-shaped cavity of the bony labyrinth containing the saccule and utricle.

Utricle

A sac in the vestibule containing a horizontal macula that responds to horizontal acceleration and head tilting.

Saccule

A sac in the vestibule containing a vertical macula that responds to vertical acceleration, such as in an elevator.

Maculae

Sensory receptor organs for static equilibrium that respond to gravity and linear acceleration.

Otoliths

Calcium carbonate ($CaCO_3$) stones found within the jellylike otolithic membrane of the maculae.

Cochlea

A spiral, conical, bony chamber about the size of a split pea that contains the cochlear duct and Organ of Corti.

Organ of Corti (Spiral organ)

The receptor organ of hearing, composed of hair cells and supporting cells located between the tectorial and basilar membranes.

Scala vestibuli

The chamber of the cochlea that begins at the oval window and is filled with perilymph.

Scala media (Cochlear duct)

The middle chamber of the cochlea filled with endolymph, bounded by the vestibular and basilar membranes.

Scala tympani

The chamber of the cochlea that terminates at the round window and is filled with perilymph.

Basilar membrane

The fibrous "floor" of the cochlear duct that supports the Organ of Corti.

Tectorial membrane

A membrane in the Organ of Corti into which the stereocilia (hairs) of hair cells are embedded.

Stereocilia

Hearing receptor hairs arranged from tallest to shortest; their bending opens or closes ion channels to generate signals.

Vestibulocochlear nerve (Cranial Nerve VIII)

The nerve that transmits auditory and equilibrium information from the inner ear to the brain.

Helicotrema

The apex of the cochlea where sounds with frequencies below the hearing range travel through without exciting hair cells.

Static balance

Maintenance of head position relative to gravity and detection of linear acceleration/deceleration.

Dynamic balance

Maintenance of body position in response to rotational or spinning movements.

Frequency

Measured in Hertz ($Hz$), it determines the pitch of a sound wave; higher frequency equals higher pitch.