Anatomy: Eye and Ear

Malleus

An auditory ossicle attached to the tympanic membrane whose head articulates with the incus and handle receives insertion of the tensor tympani muscle.

Incus

An auditory ossicle that articulates with the malleus and the stapes.

Stapes

An auditory ossicle whose body attaches to the oval window to transmit vibrations to the inner ear and serves as the attachment site for the stapedius muscle.

Levator palpebrae superioris

An extraocular muscle that elevates the superior eyelid.

Superior rectus

An extraocular muscle innervated by CN III that elevates, adducts, and medially rotates (intorts) the eyeball.

Inferior rectus

An extraocular muscle innervated by CN III that depresses, adducts, and laterally rotates (extorts) the eyeball.

Medial rectus

An extraocular muscle innervated by CN III that adducts the eyeball.

Lateral rectus

An extraocular muscle innervated by CN VI (abducens nerve) that abducts the eyeball.

Superior oblique

An extraocular muscle innervated by CN IV (trochlear nerve) that depresses, abducts, and medially rotates (intorts) the eyeball.

Inferior oblique

An extraocular muscle innervated by CN III that elevates, abducts, and laterally rotates (extorts) the eyeball.

Ciliary muscle

Smooth muscle of the ciliary body innervated by parasympathetic fibers via CN III that controls lens thickness for visual accommodation.

Sphincter pupillae

Smooth muscle of the iris innervated by parasympathetic stimulation via CN III that constricts the pupil.

Dilator pupillae

Smooth muscle of the iris innervated by sympathetic stimulation that dilates the pupil.

Tensor tympani

A middle ear muscle innervated by V3 that inserts into the handle of the malleus and tenses the tympanic membrane to reduce vibration amplitude.

Stapedius

A middle ear muscle innervated by CN VII that attaches to the stapes to limit vibration and protect the inner ear.

Optic canal

An opening at the apex of the orbit located in the lesser wing of the sphenoid bone that transmits the optic nerve (CN II).

Lacrimal gland

A tear-producing gland of the lacrimal apparatus receiving parasympathetic innervation via the greater petrosal nerve.

Lacrimal ducts

Passageways of the lacrimal apparatus that convey tears from the lacrimal gland to the eye surface.

Lacrimal canaliculi

Small canals of the lacrimal apparatus that drain tears into the nasolacrimal duct.

Nasolacrimal duct

A duct of the lacrimal apparatus that drains tears into the nasal cavity.

Anterior segment

The anterior portion of the eyeball consisting of the anterior and posterior chambers filled with aqueous humor.

Anterior chamber

The space of the eyeball located between the cornea and iris, filled with aqueous humor.

Posterior chamber

The space of the eyeball located between the iris and the lens/ciliary body, filled with aqueous humor.

Posterior segment (Vitreous body)

The posterior 80% of the eyeball filled with vitreous humor.

Aqueous humor

Fluid secreted by ciliary processes that fills the anterior and posterior chambers of the eye.

Vitreous humor

Fluid filling the posterior segment (vitreous body) of the eyeball.

Fibrous layer

The outer coat of the eyeball comprising the posterior 5/6 sclera and anterior 1/6 cornea.

Sclera

The tough, opaque "white of the eye" covering the posterior 5/6 of the eyeball that provides attachment for extrinsic and intrinsic eye muscles.

Cornea

The transparent, highly touch-sensitive anterior 1/6 of the eyeball responsible for two-thirds of the eye's optical refractive power.

Vascular layer

The middle coat of the eyeball comprising the choroid, ciliary body, and iris.

Choroid

The largest, highly vascular part of the middle layer lining most of the sclera.

Ciliary body

A vascular and muscular structure connecting the choroid to the iris that contains ciliary muscles and ciliary processes.

Ciliary processes

Projections of the ciliary body that secrete aqueous humor.

Iris

The contractile, colored diaphragm of the vascular layer containing the central pupil and muscles controlling pupillary diameter.

Pupil

The central opening of the iris whose diameter is regulated by sphincter and dilator pupillae muscles.

Retina

The innermost coat of the eyeball containing optic and nonvisual parts.

Optic part of retina

The light-sensitive portion of the inner layer containing neural and pigmented layers.

Nonvisual part of retina

The light-insensitive continuation of the retina extending over the ciliary body and posterior iris.

Neural layer of retina

The light-receptive layer of the optic retina.

Pigmented layer of retina

The non-light-receptive layer of the optic retina underlying the neural layer.

Optic disc

The point of entry for sensory fibers and vessels conveyed by the optic nerve, lacking photoreceptors ("blind spot").

Macula lutea

The specialized region lateral to the optic disc containing the highest density of photoreceptor cones for sharp, clear, central vision

Fovea centralis

The central depression of the macula lutea providing the area of greatest visual acuity.

Lens

The transparent structure behind the iris whose thickness is altered by the ciliary muscle during accommodation to refract light onto the retina.

External ear

The outer division of the ear consisting of the auricle and external acoustic meatus.

Auricle (Pinna)

The external structure of elastic cartilage covered by skin that collects sound.

External acoustic meatus

The 2–3 cm canal extending from the auricle to the tympanic membrane containing ceruminous and sebaceous glands.

Ceruminous and sebaceous glands

Glands within the external acoustic meatus that produce earwax (cerumen).

Tympanic membrane

The translucent, pearly gray membrane separating the external ear from the middle ear that vibrates in response to sound waves.

Handle of malleus

The portion of the malleus attached to the internal surface of the tympanic membrane.

Middle ear (Tympanic cavity)

An air-filled chamber in the petrous temporal bone containing auditory ossicles, muscles, and nerves.

Pharyngotympanic (Auditory) tube

A tube connecting the tympanic cavity to the nasopharynx that equalizes middle ear pressure with atmospheric pressure.

Labyrinthine wall

The medial wall of the middle ear separating it from the internal ear, featuring the promontory, oval window, and round window.

Oval window

The membrane-covered opening in the labyrinthine wall to which the base of the stapes attaches.

Round window

The membrane-covered opening in the labyrinthine wall that acts as a pressure valve to dampen fluid waves in the cochlea.

Inner ear (Internal ear)

The internal division housing the vestibulocochlear organ for hearing and equilibrium, consisting of bony and membranous labyrinths.

Bony labyrinth

A fluid-filled space within the petrous temporal bone containing the vestibule, semicircular canals, and cochlea.

Vestibule

The oval chamber of the bony labyrinth containing the utricle and saccule.

Utricle

A sac within the vestibule of the vestibular labyrinth that detects linear acceleration.

Saccule

A sac within the vestibule of the vestibular labyrinth that detects linear acceleration.

Semicircular canals

Three bony canals (anterior, posterior, lateral) housing the semicircular ducts.

Cochlea

The spiral bony canal housing the cochlear duct for audition.

Membranous labyrinth

A series of fluid-filled communicating sacs and ducts suspended within the bony labyrinth.

Vestibular labyrinth

The division of the membranous labyrinth comprising the utricle, saccule, and semicircular ducts concerned with balance.

Semicircular ducts

Three ducts within the semicircular canals that detect angular acceleration.

Cochlear labyrinth (Cochlear duct)

The division of the membranous labyrinth within the cochlea containing the spiral organ.

Spiral organ (Organ of Corti)

The receptor organ for auditory stimuli located within the cochlear duct containing hair cell