Unit 5: Senses Structure of the Ear

Major functions of the ear 1.Hearing 2. Balance/Equilibrium *Sound waves and fluid movement act on receptors called hair cells that generate nerve impulses

Three sections of the ear External Ear Middle Ear Inner Ear

External Ear – Auricle or Pinna – External Acoustic Meatus (ear canal- previously learned as the hole in the temporal bone of the skull)

External Ear – Tympanic membrane (ear drum): Stretches across ear canal separating it from middle ear – Ear examinations: otoscope used to observe external ear canal and surface of tympanic membrane

Cerumen Wax that accumulates in auditory canal – Secreted by modified sweat gland to moisturize, fight infection, and prevent dirt and dust from entering your inner ear

Otitis Media Ear infection: structure of auditory tube makes middle ear prone to bacterial and viral infections Causes:  Inflammation and redness in eardrum  Fluid build up in middle ear

Middle Ear: Tympanic cavity Inside cavity in temporal bone Contains 3 Ossicles (tiny bones): 1.Malleus: “handle” of malleus connects to inner surface of ear drum 2.Incus 3.Stapes: looks like a stirrup, vibrates against oval window of inner ear

Middle Ear Ossicles

Middle Ear Openings – Middle ear openings: routes for infections to enter ear External acoustic meatus Oval window and Round window: both open to inner ear Mastoid air spaces in temporal bone

Middle Ear Openings Eustachian tube (Auditory tube) – Connects middle ear to nasopharynx (throat behind the nose) to drain fluid from middle ear – Equalizes air pressure between ear and nose/throat when you yawn or swallow by pushing air rapidly through tube toward tympanic membrane

Inner Ear: Bony Labyrinth Vestibule: balance Cochlea: hearing Semicircular canals: balance

Cochlea and Cochlear Duct Cochlea= “snail” – Spiral shaped tube that connects to Cochlear Nerve (Auditory Nerve) to transmit nerve impulses to brain (transmits sound)

Cochlear duct: structure of ear for HEARING Fluid filled space inside cochlea Lined with hair cells on Organ of Corti= hearing sense organ that lines duct