Ear Flashcards
What is the external ear composed of?
Elastic cartilage covered with integument
What is the lobule composed of?
NO cartilage, just loose connective tissue
What is the blood supply to the external ear?
Posterior auricular artery and superficial temporal artery both off of the external carotid
What is the sensory innervation for the external ear?
Auriculotemporal (v3) and greater auricular (c2,c3)
What type of glands does the external acoustic meatus contain?
Ceruminous glands - make wax
What does the external acoustic meatus lead to?
A canal that leads to the tympanic membrane
What is the function of the tympanic membrane?
Moves with sound and transmits to ossicles
What type of epithelium is the external surface of the tympanic membrane comprised of?
Stratified squamous epithelium
What type of epithelium is the internal surface of the tympanic membrane comprised of?
Simple cubiodal epithelium
What innervates the tympanic membrane?
Auriculotemporal (external) and branches of vagus (internal)
What can cause a perforated tympanic membrane?
Increase in middle ear pressure from fluid or barotrauma; or from external trauma
What should you not give patients with a perforated tympanic membrane?
Gentamicin
What separates the external ear and the middle ear?
Tympanic membrane
What are the 2 parts of the middle ear?
Epitympanic recess and tympanic cavity
Medial border of middle ear
Labyrinth wall
Anterior border of middle ear
carotid wall and opening of pharyngotympanic tube
Posterior border of middle ear
Mastoid wall
Floor of middle ear
Jugular wall
Roof of middle ear
Tegmental wall
What nerves can be seen running in the middle ear?
Chorda tympani and lesser petrosal nerve
What passes between malleus and incus?
Chorda tympani
What are the ossicles of the middle ear and what is their purpose?
Malleus, incus, stapes - amplify and transmit vibrations from tympanic membrane to oval window
What connects the tympanic cavity to the nasopharynx?
Pharyngotympanic tube (Eustachain tube)
Purpose of pharyngotympanic tube?
Equalize pressure
What is the pharyngotympanic tube made of?
Bone and mostly elastic cartilage
What muscles open the pharyngotympanic tube?
Tensor veli palatini, levator veli palatini, salpingopharyngeus
What are the muscles in the middle ear?
Tensor tympani and stapedius
What is the action and innervation of tensor tympani?
Action = reduce amplitude of sound by tensing tympanic membrane
IN: CN V
What is the action and innervation of stapedius?
Action = Prevent excessive movement of stapes and reduce oscillatory range
IN: CN VII
Otitis media
Middle ear infection, accumulation of fluid/pus that causes ear pain
Tympanic membrane appears red and swollen
What happens if otitis media goes untreated?
Impaired hearing and scarred ossicles and possibly mastoiditis
Mastoiditis
Infection of mastoid process cells that can spread into cranial fossa via petrosquamous cranial suture
What 2 labyrinths does the inner ear consist of?
Bony and membranous
Where is the membranous labyrinth?
Inside the bony labyrinth
What fluid does the bony labyrinth contain and where does it drain?
Perilymph and it drains via perilymphatic duct (cochlear aqueduct) and into subarachnoid space
What fluid does the membranous labyrinth contain and where does it drain?
Endolymph and it drains via endolymphatic duct and into dural venous sinuses
Composition of perilymph?
Similar to CSF - high na, H, ca; and low K
Composition of endolymph?
High K and low na
Source of endolymph?
Stria vascularis
Describe the setup of hair cells
Multiple stereocilia that increase in height along a certain direction with one kinocilia that is the tallest
If the stereocilia are moved toward kinocilia what happens?
mechanoelectric K+ channels will open
If the stereocilia are moved away from kinocilia what happens?
Mechanoelectric K+ channels will close
What type of nerves supply hair cells?
Afferent and Efferent (modulate sensitivity)
Where will you find hair cells?
Cochlear duct, macula, ampulla
What do the hair cells interact with in the organ of corti to move back and forth?
Tectorial membrane
What makes up the cochlea?
Scala vestibuli, scala media, and scala tympani
What are scala vestibuli and scala tympani made of?
Perilymph
What does the stapes vibrate on?
Oval window
What does the stapes vibrations cause?
Fluid vibrations within the scala vestibuli and onward
Cochlear duct
Scala media
What vibrates with sound and helps to move the hair cells?
Basilar membrane
Basilar membrane and hair cells in the scala media (cochlear duct) that senses sound
Organ of corti
Where do high pitch/frequencies go on the basilar membrane?
Base - not very far down it
Where do low pitch/frequencies go on the basilar membrane?
Apex - travel far down it
Where are the utricle and saccule?
In the vestibule (bony labyrinth)
What is housed within the utricle and saccule?
Each has a macula
What does the macula do?
Senses gravity and linear acceleration
Describe the setup of a macula
A gelatinous membrane = otolithic membrane that has calcium carbonate crystals on it = otoconia that both sit on top of hair cells
What is within the semi-circular canals?
Semi-circular ducts
What is within the semi-circular ducts?
Ampullas
What do ampullas do?
Sense rotation and dynamic equilibrium
What is the structure within the ampulla that gets pushed by endolymph when rotation occurs?
Cupulla
Where does the cupulla sit?
On top of hair cells
What makes up the inner ear?
Cochlea, vestibule, semi-circular canals
Hearing loss that effects the external and middle ear
Conductive hearing loss
Hearing loss that effects the inner ear, is noise and age related
Sensorineural hearing loss
Hearing loss due to problems in the CNS
Central hearing loss
Meniere’s syndrome
Increased endolymph volume that causes dizziness, vertigo, high-pitched rushing sound and some hearing loss
Viral labyrinthitis
Same symptoms as meniere’s syndrome but is only present for about one week and then goes away
