Anatomy of the Tympanic Cavity and Inner Ear Structures

ensor tympani muscle

located on the anterior wall of the tympanic cavity, attaches to the malleus

Mesotympanum

the middle portion of the tympanic cavity

Hypotympanum

inferior portion of the tympanic cavity, crescent-shaped

Stapedius muscle

located on the posterior wall of the tympanic cavity and attaches to the stapes

pars tensa

the taut part of the tympanic membrane

the tympanic membrane

the lateral border of the tympanic cavity; composed of three distinct layers; cone-shaped

Eustachian tube

connects the middle ear to the nasopharynx; maintains pressure equalization in the tympanic cavity

pars flaccida

the loose part of the tympanic membrane

Annulus

a ring-shaped ligament that holds the tympanic membrane in place

Epitympanum

superior portion of the tympanic cavity, also called the attic

tensor veli palatini muscle

attached to the cartilaginous portion of the Eustachian tube; contraction of this muscle opens the Eustachian tube during swallowing and yawning

Stria vascularis

lateral border of the Organ of corti; serves as a pump to provide a supply of blood and pump K+ into the scala media

bony labyrinth

cavity that contains the inner ear; located within the petrous portion of the temporal bone

Modiolus

the central bony channel of the cochlea

Membranous labyrinth

an endolymph-filled structure enclosed by a membrane that is located within the bony labyrinth

Internal auditory canal

bony canal in the petrous portion of the temporal bone through which CN VII and CN VIII travel (and eventually exit the skull here)

scala vestibuli

the part of the cochlear portion of the bony labyrinth that extends along the length of the cochlea from the vestibule to the helicotrema

scala tympani

the part of the cochlear portion of the bony labyrinth that extends along the length of the cochlea from the helicotrema to the round window

scala media

the cochlear portion of the membranous labyrinth

Perilymph

the fluid found in the scala tympani and scala vestibuli; high in Na+ and low in K+

Endolymph

the fluid found in the scala media; high in K+ and low in Na+

Helicotrema

a narrow passageway at the apex of the cochlea; connects the scala vestibuli to the scala tympani

Stereocilia

tiny hair-like projections from one end of the hair cell; they are responsible for the transduction of mechanical motion into electrochemical impulse

Organ of corti

the sense organ of hearing that runs along the entire length of the basilar membrane, contains the OHC, IHC, and support cells

Basilar membrane

the border between the scala media and the scala tympani; physical properties change from the base of the cochlea to the apex