Ear Structure & Function 10 January 2017

Anatomy of the Ear External Ear Structures: Pinna auditory canal ear drum Function: Funnel and conduct sound to middle ear

Anatomy of the Ear Middle Ear Structures: Ossicles Malleus Incus Stapes Eustacian / auditory tube Function: Amplify and conduct sound to inner ear

Anatomy of the Ear Inner Ear Structures: Osseous labyrinth Semicircular canals Vestibule cochlea Function: Receive sound and equilibrium stimuli

Anatomy of the Ear NOTE: Diagrams are misleading. The entire inner is bony, except for the labyrinth which is a series of cavities (spaces) within the bone.

Outer (External) Ear Function:

Outer (External) Ear Function: to funnel and conduct sound to the middle ear Pinna collect sound waves and direct to the tympanic membranes … but in humans, not very effectively. Cerumen (ear wax) lines the external auditory canal. Antibacterial Also discourages bugs, mold, etc. Lubricates ears Helps trap / remove foreign particles The tympanic membrane (ear drum) vibrates when sound waves hit it, transmitting the sound to the middle ear A reflex tightens the ear drum in response to loud, low-pitched sounds – this reduces the sound transmitted to the ear and protectes our hearing

Disorders of the Outer Ear Ear Wax Blockage Ear wax can become impacted, usually from hearing aid use or inappropriate methods of cleaning the ears Can cause temporary loss of hearing Now hear this! Stop cleaning your ears! Guidelines by the American Association of Otolaryngology were updated in Dec 2016 to be more strongly worded

Disorders of the Outer Ear Otitis Externa (Swimmer’s Ear) Infection of external auditory ear canal, usually due to excess moisture in the ear canal (such as from swimming), though cuts and scrapes to the ear canal can also become infected. In addition Picture through an otoscope. Notice that the canal is red but the ear drum is clear and not bulging.

Middle Ear Function: In addition

Middle Ear Function: to AMPLIFY the sound and conduct it to the oval window of the inner ear. How? The tympanic membrane transmits sound to the three ossicles. The ossicles act like levers, amplifying the sound and transmitting it to the oval window, a membrane-covered opening to the inner ear. In addition

Eustachian Tubes Structure Tube that connects the middle ear to the nose and throat Mostly closed, but opens when we move our jaw Why do we have it? Equalize pressure in the middle ear Drain fluids to the throat This is why its helpful to yawn or chew gum on a plane ride Remember: the tympanic membrane seals the middle ear from the outer ear – so the only way for air / fluids to leave the middle ear is through the eustachian tubes In addition

Disorders of the Middle Ear Otitis media (middle ear inflammation / infection) – Inflammation (often with the buildup of infected fluids) within the middle ear Visible with an otoscope as a bulging eardrum Usually caused from a respiratory infection Babies who are allowed to drink bottles while lying down are also very likely to get ear infections Much more common in young children, because their Eustachian tubes are narrower and more horizontal In addition

Disorders of the Middle Ear myringotomy– Ear tubes are often recommended for children who experience chronic middle ear infections or fluid build-up The tube is placed in the ear drum, but performs the functions of a eustachian tube – ventilating and draining the middle ear. In addition

Hearing & the Inner Ear Hearing takes place within the cochlea of the inner ear. Cochlea is a long, curled cavity with three layers 2 layers of perilymph – a plasma-like fluid In-between: a system of membranes that contain the organ of Corti and the mechanoreceptors (hair cells) that create the nerve impulse In addition

Hearing & the Inner Ear The top diagram is a cross-section of the cochlear cavity. Take a moment to figure out … What fills the scala vestibuli? The scala tympani? The cochlear duct? In addition

Hearing & the Inner Ear When the stapes beats against the oval window, it causes pressure waves within the perilymph The movement of the perilymph disturbs the cilia (receptors) of the Organ of Corti, generating a nerve impulse Different frequencies (pitch) vibrate the membrane in different locations. High pitches are heard that the front, low at the back. In addition

Hearing & the Inner Ear When the stapes beats against the oval window, it causes pressure waves within the perilymph The movement of the perilymph disturbs the cilia (receptors) of the Organ of Corti, generating a nerve impulse The round window is a membrane-covered opening just below the oval window. It bulges to keep the pressure waves from bouncing back. In addition Watch me! Just for fun!

Closure What were our objectives, and what did you learn about them? What was our learner profile trait and how did we exemplify it? How does what we did today address our unit question?