SS Lecture 7 Review- Ear Anatomy & Physiology of Hearing

External Ear Anatomy

Functions of the Ear

Middle Ear Anatomy

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Lecture 7 Review

Ear Anatomy & Physiology of Hearing

Age Related Hearing Changes

Physiology of Hearing

Inner Ear Anatomy

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Lecture 7 Review Completed!

Age Related Hearing Changes

• Atrophy of the Cochlea and nerve fibers can lead to hearing loss and balance problems with aging.
• Presbycusis:
• Age related sensorineural hearing loss.
• Obstruction of the External Ear canal (which can result in diminished hearing) can be caused by:
• Cerumen (earwax)
• Hair growth

• The External Ear & Middle Ear are separated by the Tympanic Membrane (Eardrum).
• Three Auditory Ossicles (Small Bones) in the Middle Ear:
• Malleus ("hammer")
• Incus ("anvil")
• Stapes ("stirrup")
• Oval Window
• Connected to the Stapes.
• Separates the Middle Ear from the Inner Ear.
• Eustachian Tube
• Extends from the Middle Ear to the Nasopharynx - equilizes air pressure.

Middle Ear Anatomy

Auditory Ossicles send sound waves from the Tympanic Membrane to the Inner Ear

Video describing the Physiology of Hearing.

• Auricle (aka Pinna)
• Visible external portion of the ear.
• Acoustic Meatus
• Opening in the Auricle.
• External Auditory Canal
• Extends from the Acoustic Meatus to the Tympanic Membrane and is lined with cells that produce Cerumen (earwax).
• Tympanic Membrane (aka Eardrum)
• Shiny pearl gray membrane that vibrates when hit by sound waves.

• Lymph Nodes Surrounding the Ear
• Pre-Auricular Lymph Nodes (in front of the ear).
• Post-Auricular Lymph Nodes (behind the ear).
• Sub-Mandibular Lymph Nodes (below the ear).

External Ear Anatomy

Functions of the Ear

• Hearing:
• When sound waves enter the ear canal, the tympanic membrane (eardrum) vibrates. This vibration passes on to three tiny bones (ossicles) in the middle ear. The ossicles amplify and transmit these sound waves to the inner ear. Once the sound waves reach the inner ear, tiny hair cells transform the vibrations into electrical energy and send it along nerve fibers to the brain.

• Balance (Position Sense & Equilibrium):
• The inner ear contains semicircular canals with fluid and hair-like sensors. When moving the head, the fluid inside these loop-shaped canals sloshes around and moves the hairs. The hairs transmit this information along the vestibular nerve to the brain. Finally, the brain sends signals to the muscles to maintain balance.

Inner Ear Anatomy

• Bony Labyrinth:
• Filled with Perilymph Fluid.
• The Bony Labyrinth is made of three structures:
• Vestibule - has receptors that maintain balance.

• Semicircular Canals - has receptors that detect movement and provide equilibrium.
• Cochlea - transmits sound from the Oval Window to the Vestibulocochlear Nerve (Cranial Nerve VIII).
• Membranous Labyrinth:
• Filled with Endolymph Fluid.
• Contained within the Bony Labyrinth.

The Inner Ear has two important jobs: Hearing & Balance!