eyes and ears

External ear

Collects and directs sound into the ear

Auricle (pinna)

Collects and directs sound waves into the auditory canal and toward the tympanic membrane

External acoustic meatus (auditory canal)

Canal lined with glands that secrete cerumen (earwax) to lubricate and protect the ear

Cerumen

Earwax that lubricates and protects the ear

Tympanic membrane (eardrum)

Separates the external and middle ear and vibrates when struck by sound waves

Middle ear

Air-filled cavity that transmits sound vibration

Ossicles

Three small bones that mechanically transmit sound vibrations

Malleus

First ossicle (hammer) that transmits vibrations from the eardrum

Incus

Second ossicle (anvil) that passes vibrations to the stapes

Stapes

Third ossicle (stirrup) that transmits vibrations to the oval window

Eustachian tube

Tube connecting middle ear to throat that equalizes air pressure

Inner ear

Contains structures for hearing and balance

Labyrinth

Maze-like network of canals in the inner ear

Perilymph

Fluid between the bony and membranous labyrinth

Endolymph

Fluid within the membranous labyrinth

Cochlea

Spiral-shaped structure containing the organ of Corti for hearing

Organ of Corti

Structure on the basilar membrane containing hair cells for hearing

Hair cells

Sensory receptors that detect vibrations and send signals for hearing

Vestibule —

Structure containing utricle and saccule for balance

Utricle

Contains hair cells that respond to gravity and movement

Saccule

Works with utricle to detect position and movement

Otoliths

Calcium carbonate crystals that help detect gravity and movement

Semicircular canals

Three canals that detect changes in head position

Eighth cranial nerve (auditory nerve)

Carries impulses for hearing and balance to the brain

Auditory-evoked response

Measures brain response to sound

Electronystagmography (ENG)

Records eye movements related to balance

Audiometry

Measures hearing ability using sound tones

Otoscopy

Visual exam of ear canal and eardrum

Rinne test

Compares bone conduction to air conduction hearing

Tympanometry

Measures movement of eardrum and middle ear pressure

Eye

Organ of vision composed of structures that work together to produce sight

Cornea

Transparent front part of the eye that bends light and helps focus it

Pupil

Opening in the center of the iris that allows light to enter

Lens

Structure that sharpens the focus of light on the retina

Vitreous body

Jellylike substance that maintains the shape of the eyeball

Retina

Innermost layer containing photoreceptors that convert light into nerve impulses

Rods

Photoreceptors sensitive to dim light and used for night vision

Cones

Photoreceptors responsible for color and detailed vision

Optic nerve

Transmits visual impulses from the retina to the brain

Orbit

Cone-shaped cavity in the skull that contains the eyeball

Eye muscles

Six muscles that control movement of the eyeball

Eyelids

Protect the eye and keep it moist

Conjunctiva

Mucous membrane that protects and lubricates the eye

Lacrimal apparatus

Produces, stores, and removes tears

Lacrimal gland

Produces tears that cleanse and lubricate the eye

Lacrimal canaliculi

Ducts that collect tears and drain into lacrimal sac

Lacrimal sac

Collects tears and drains into nasolacrimal duct

Nasolacrimal duct

Drains tears into the nose

Sclera

White outer layer of the eye

Choroid

Pigmented layer that prevents internal reflection of light

Ciliary body

Muscle that changes shape of lens and produces aqueous humor

Iris

Colored part of the eye that regulates amount of light entering

Macula lutea

Area of retina responsible for sharp vision

Fovea centralis

Central point of sharpest vision containing only cones

Optic disk

Area with no rods or cones; creates blind spot

Aqueous humor

Watery fluid in anterior cavity that nourishes eye

Vitreous humor

Jellylike fluid in posterior cavity that maintains shape

Accommodation

Process of changing lens shape to focus on objects

Myopia

Nearsightedness; difficulty seeing distant objects

Cataract

Clouding of the lens

Visual acuity

Sharpness of vision measured by Snellen chart

Ophthalmoscopy

Examination of the interior of the eye

Tonometry

Measurement of intraocular pressure

Keratometry

Measurement of cornea curvature

Ocular ultrasonography

Uses sound waves to examine eye structures

Color vision test

Detects ability to distinguish colors