Outer Ear
What is the outer ear composed of?
the pinna, ear canal, and the ear drum
what are the names of the two middle ear muscles?
stapedius and tensor tympani
What are the 2 sacs in the vestibule called and what kind of motion and plane do each respond to?
1. Utricle: linear acceleration in a horizontal plane
2. Saccule: linear acceleration in a vertical plane
True or false: The CANS is primarily an afferent system.
True
Name one disorder of the outer ear
Microtia/Anotia, atresia, cauliflower ear, keloids, otitis externa, foreign body obstruction, tympanosclerosis, collapsing canals
How do you examine the EAC of adults vs children.
During an otoscopy, for children you pull down and back. For adults you pull up and back.
What are the three layers of the tympanic membrane?
Lateral surface
Middle surface
Medial/internal surfaces
How many rows of IHCs and OHCs are there and state which ones are embedded into the tectorial membrane.
IHC have one row (Not in direct contact with the tectorial membrane)
OHC have 3-5 rows (stereocilia embedded in the tectorial membrane)
Where is tonotopicity preserved?
Auditory nerve, cochlear nucleus, and in the primary auditory cortex (Heschl's Gyrus)
Name and describe a middle ear disorder.
Negative middle ear pressure - Auditory tube is not equalizing pressure (not acoustically transparent)
Suppurative otitis media - bacterial infection of the middle ear (pus)
Cholesteatoma - collection of skin cells and cholesterol in a sac within the middle ear
Mastoiditis - Fluid accumulating in middle ear invades the mastoid cavity
Otosclerosis - Spongy, bony growth on the stapes footplate
Which outer ear disorder is resulted from trauma in the ear and which one happens when scar tissue is produced excessively?
cauliflower ear / keloid
What two middle ear pathologies can NOT be seen during otoscopy?
An infection on CN 7 for Bell's palsy, and otosclerosis
Name the three small parts of the cochlea
Scala tympani, scala media, and scala vestibuli
What is Vestibular Schwannoma and what is it diagnosed by?
Neoplasms, arise from Schwann cells of the vestibular portion of CN IIIV; Usually unilateral
Diagnosed by basic audiological test battery, ABR, CT Scan, MRI, PET Scan
What are the three types of hearing loss and briefly explain each.
1. Conductive: Occurs when there is an issue/damage to the outer ear and/or middle ear
2. Sensorineural:Occurs when there is an issue/damage to the inner ear and/or beyond
3. Mixed: Occurs when there is an issue/damage to the outer ear and/or middle ear WITH the inner ear and/or retrocochlear origin
What are the major landmarks on the tympanic membrane?
Cone of light, Umbo, Manubrium of the malleus, Pars tensa, Pars flaccida, Annulus
Describe otoacoustic emissions.
generated by OHC motility; OAE'S are present when OHC's are healthy and absent when they are damaged
Name the two cochlear fluids, their chemical composition and where they are found.
Endolymph is found in the scala media and has high potassium/low sodium.
Perilymph is found in the scala vestibuli and scala tympani. It has high sodium/low potassium.
Name the different parts of the ascending auditory pathway.
Distal auditory nerve
Proximal auditory nerve
Cochlear nucleus
Superior Olivary Complex
Lateral Lemniscus
Inferior colliculus
Medial Geniculate Body
Auditory Cortex
True or false: Ear tubes are considered a disorder.
False, tubes are a form of treatment
what is the outer ear responsible for?
gathering acoustic energy from the environment and funneling them down into the ear canal
Identify the three middle ear transform mechanisms and also say whether they increase force or reduce area.
1. Vibrating area of tympanic membrane (reduce area)
2. Lever Action (increase force)
3. Buckling Effect (increase force)
Describe the traveling wave theory.
Today's accepted hearing theory, when sound comes from the outer ear and travels through the middle ear and arrives at the stapes footplate. The rocking motion of stapes footplate causes downward and upward motion of the basilar membrane due to the disturbance in the endolymph. The wave travels from base to apex with a pitch perception is determined by rate of basilar membrane ossilation and loudness perception occurs by the degree of displacement.
Name the disorder of cochlear nuclei: Changes in central auditory nervous system caused by conductive hearing loss in early life. Neural plasticity causes neurons to reroute to acclimate to understimulated CANS. The result is difficulty in language learning.
Minimal Auditory Deficiency Syndrome
Name the for prenatal, perinatal, and postnatal disorders.
Prenatal: Syndromic and non syndromic hearing disorders, CHARGE syndrome, cerebral palsy, drugs, congenital infections (CMV, anoxia, rubella etc.)
Perinatal: anoxia, premature birth, head trauma
Postnatal: meningitis, barotrauma, viral infection