Ch. 13 MC Ear

Function of the ear

The two functions of the ear are to hear and to provide the sense of balance. The ear is made up of three parts: the external ear, the middle ear, and the inner ear. The process of hearing begins with the auricles directing sound waves into the external auditory canal. As the sound waves ripple through the external ear, the tympanic membrane vibrates. The ossicles in the middle ear carry the vibration to the inner ear, where the stimulus is transmitted by the cochlear nerve to the brain and is interpreted as sound. Balance is a function of the inner ear and is maintained through a series of complex processes. The vestibular nerve transmits information about motion and body position from the semicircular canals and the vestibule to the brain for interpretation.

presbycusis

hearing impairment occurring with (old) age

otitis media (OM)

inflammation of the middle ear

otitis externa

inflammation of the outer ear

ear

organ of hearing and balance; includes the external ear, middle ear, and labyrinth or inner ear

labyrinth

bony spaces within the temporal bone of the skull made up of three distinct parts, the cochlea, the semicircular canals, and the vestibule. The cochlea facilitates hearing. The semicircular canals and the vestibule facilitates equilibrium and balance.

Meniere disease

chronic disease of the inner ear characterized by a sensation of spinning motion (vertigo), ringing in the ear (tinnitus), aural fullness, and fluctuating hearing loss; symptoms are related to a change in volume or composition of fluid within the labyrinth

cochlea

coiled portion of the inner ear containing the sensory organ for hearing; connects to the oval window in the middle ear

external ear

consists of the auricle and external auditory canal (meatus)

inner ear

consists of the labyrinth and connectors of the vestibular and the cochlear nerves

middle ear

consists of the tympanic membrane and the tympanic cavity containing the ossicles

cholesteatoma

cystlike mass composed of epithelial cells and cholesterol occurring in the middle ear; may be associated with chronic otitis media

auricle

external, visible part of the ear located on both sides of the head; directs sound waves into the external auditory canal (also called pinna)

tympanic membrane

semitransparent membrane that separates the external auditory meatus and the middle ear cavity. The tympanic membrane transmits sound vibrations to the ossicles. (also called eardrum)

vertigo

sense that either one's own body (subjective vertigo) or the environment (objective vertigo) is revolving; may indicate inner ear disease

semicircular canals and vestibules

sensory organs of balance; contain receptors and endolymph that provide sensory information about the body's position to maintain equilibrium

external auditory canal

short tube that ends at the tympanic membrane. The inner part lies within the temporal bone of the skull and contains the glands that secrete earwax (cerumen). (also called external auditory meatus)

acoustic neuroma

benign tumor within the internal auditory canal growing from the acoustic nerve (cochlear branch of the vestibulocochlear nerve); may cause hearing loss and may damage structures of the cerebellum as it grows

ossicles

bones of the middle ear that carry sound vibrations. The ossicles are composed of the malleus (hammer), incus (anvil), and stapes (stirrup). The stapes connects to the oval window, which transmits the sound vibrations to the cochlea of the inner ear.

Eustanchian tube

passage between the middle ear and the pharynx; equalizes air pressure on both sides of the tympanic membrane

mastoid bone

portion of the temporal bone of the skull posterior and inferior to each auditory canal; contains mastoid air cells that drains into the middle ear behind the external auditory canal. (also called mastoid process)

tinnitus

ringing in the ears