Lecture 24: Functional anatomy of the ear; audition

Question 1

External ear

Answer 1

• Manubrium (footplate) of malleus: separates two parts of tympanic membrane.
• Tympanic membrane: pars tensa (carries vibrations)
• Tympanic membrane: pars flaccida (air and balance)
• Ear flap = pinna/auricle. Capturing device.
• External auditory canal, cartilaginous tube lined with skin.

external ear ends at tympanic membrane

In dogs, 90 degree turn in ear causes a problem because things get stuck in there.
serumen= ear wax

Question 2

Middle ear

Answer 2

• Got tympanic bulla here (filled with air) Air has mechanism to equalize pressure.
• Auditory tube: connection to nasopharynx.
• Auditory ossicles: Malleus (hammer), Incus (anvil), Stapes (stirrup) - Attached to oval/vestibule window, Epitympanic recess above auditory ossicles

all contained in tympanic bone, is air filled space

Question 3

inner ear

Answer 3

• membranous labyrinth :Bagpipe part. Long thin tube: full of fluid (endolymph), called cochlear duct
• Osseus labyrinth (series of chambers in the bone). Perilymph present here, outside of endolymph, in the scala vestibuli above the cochlear duct, and below is scala tympani.

Question 4

types of deafness

Answer 4

• Conduction deafness: problems with mechanical transmission of vibration
• Sensorineural deafness: to level of hair cells to auditory cortex. (common)
• Peripheral vs central lesions

The spiral ganglion to auditory systems what DRG is to spinal nerves

Almost invariably, deafness in one or both ears is a result of peripheral lesion, not central.