Special Senses- The Ear Module 13

The Ear at a Glance Function of the Ear Structures of the Ear Contains sensory receptors for hearing and equilibrium (balance) Structures of the Ear Auricle External ear Middle ear Inner ear

Anatomy and Physiology Otology (Oto) is study of the ear Audiology is study of hearing disorders Ear responsible for two senses: Hearing Equilibrium or sense of balance Sensory information carried to brain by vestibulocochlear nerve Cochlear nerve – hearing information Vestibular nerve – balance information

The Ear Ear is subdivided into three regions: External ear Middle ear Inner ear

External Ear Auricle or pinna Only portion visible Captures sound waves Directs them through external auditory meatus

External Ear Auditory canal Cerumen Sound moves along canal Produced by oil glands in auditory canal Oily wax slowly flows out of ear canal removing dirt that has stuck to it

External Ear Tympanic membrane Commonly called eardrum Sound waves strike membrane Causes it to vibrate Tympanic membrane separates external ear from middle ear

The internal structures of the outer, middle, and inner ear.

The Middle Ear Small cavity Located in temporal bone of skull Contains three tiny bones called ossicles Malleus Incus Stapes

Ossicles Tympanic membrane vibrates incus Vibrations amplify as they move from one ossicle to next Stapes transmits vibration to oval window Start of inner ear

Eustachian Tube Also called auditory tube Connects nasopharynx with middle ear Opens with each swallow Equalizes pressure between middle ear cavity and atmospheric pressure

The internal structures of the outer, middle, and inner ear.

Inner Ear Labyrinth Contains sensory organs Cavity within temporal bone Houses inner ear Contains sensory organs

Sensory Organs of Inner Ear Hearing Cochlea Organs of Corti Equilibrium Semicircular canals Utricle Saccule

How We Hear Sound waves travel down external auditory canal, strike eardrum Eardrum vibrates

How We Hear Ossicles conduct vibrations across middle ear from eardrum to oval window Oval window movements initiate vibrations in fluid that fills cochlea Fluid vibrations strike hair cells, bending small hairs and stimulating nerve endings Nerve ending sends electrical impulse to brain on cochlear portion of vestibulocochlear nerve

Hearing Loss Conductive hearing loss Disease or malformation of outer or middle ear All sound is weaker and muffled since it is not conducted correctly to inner ear Sensorineural hearing loss Damage or malformation of inner ear (cochlea) or the cochlear nerve Sounds are distorted because nerve impulse is incorrect

REMEMBER Pronunciation of terms test is due at end of module 14. Have any questions- post on the discussion board!

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