Ear Flashcards
What are the functions of the external ear?
- protects the eardrum and collects sound waves and sends to tympanic membrane
what is the function of the middle ear?
- function to amplify and convert sound waves into mechanical energy
What is the function of the inner ear?
- receives mechanical energy and converts it into a fluid wave
- receptors of the inner ear respond to the fluid vibrations for the perception of sound “interpret”
- sensory cells for hearing
What funnels sound into tympanic membrane?
pinna
The external canal is surrounded by skin with glands that produce what?
- cerumen
- protective function
- can get impacted
What seperates the external from middle ear?
Tympanic membrane
Label these portions of the external ear
What does sensory innervation of the external ear?
What is the outside and inside of tympanic membrane composed of?
- skin is external
- mucous membrane is internal
- moves in response to air vibrations
What bone moves when the tympanic membrane moves?
- Malleus
- Pars tensa:
- Handle of malleus (manubrium) is embedded in tympanic membrane on the medial side of the membrane
- manubrium draws membrane medially creating a depression
- the greatest point of concavity = umbo
- cone of light (base projected anteroinferiorly in a healthy ear) when viewed with an otoscope
- caused by noce
What bone is the middle ear located?
petrous bone
lined with mucous membrane
What is the tube that:
- equalizes pressure between middle ear and external environment
- allows for drainage of middle ear
Pharyngotympanic tube
What are the regions of the middle ear cavity?
Typanic cavity
Epitympanic cavity
WHat are the contents of the middle ear cavity?
- malleus, incus stapes
- synovial joints between articulations
- manubrium embedded in tympanic membrane
- footplate of stapes on oval windom
- conduct vibrations from tympanic membrane to fluid filled chamber of the cochlea
What CN innervates stapedius muscle?
- CN VII
- pulls it off oval window
What CN innervates tensor tympani muscle attached to malleus?
CN V3
- pulls it off tympanic membrane
What is the purpose of the stapedius and tensor tympani muscle?
- Both contract reflexively in response to loud sound
- tense the tympanic membrane or
- move foot plate of stapes off oval window of cochlea
- dampen the sound and preventing damage to inner ear
What nerve does taste to anterior 2/3 of the tongue and parasympathetic fibers to sublingual and submandibular gland
- it is inside the tympanic cavity
Chorda tympani is a branch of facial nerve (CN VII)
What nerve joins with nerves from carotid plexus to form lesser petrosal nerve carrying parasympathetic fibers to the parotid gland?
Tympanic nerve (CN IX)
What is the thin plate of bone separating tympanic cavity from dura mater on floor of mid cranial fossa?
Roof-tegmen tympani
What is the layer of bone separating the tympanic cavity from superior bulb of internal jugular vein (posteriorly)?
Floor of tympanic cavity
What part of the tympanic cavity is the tympanic membrane:
- handle of malleus attached to tympanic membrane
- chorda tympani nerve crosses between incus and malleus
- head of malleus located in the epitympanic recess superiorly
Lateral wall
What is the outermost coil of the cochlea, tympanic plexus on its wall?
Promontory
What is medial to footplate of stapedius, above and behind promontory
Oval window (fenestra vestibuli)
What can occur in these regions
Your tonsil can enlarge and close off pharyngotympanic tube and you are more susceptible to middle ear infections
Where are the mastoid air cells located?
Mastoid antrum
Describe the course of facial nerve
- Facial nerve enters internal auditory meatus along with vestibulocochlear nerve
- geniculate ganglion contains sensory nerve cell bodies for special sense to the taste buds to anterior 2/3 the tongue
- Greater petrosal carrying parasympathetic fibers to pterygopalatine ganglion
- chorda tympani special sense to taste buds on anterior 2/3 of tongue (lingual, a branch of V3, carries general sense to anterior 2/3 of the tongue
- lesser petrosal carrying parasympathetic fibers from glossopharnygeal (CN IX) and sympathetic fibers from carotid plexus
What is the dense bone that encases the sense organs for hearing and balance?
Otic capsule
What is the fluid within the membranous labryrinth?
- Similar in compostion to intracellular fluid
- produced by specialized cells in the membranous labyrinth
- Membranous labrynth:
- utricle and saccule
- semicircular ducts
- cochlear duct
Endolymph
- can be absorbed and stored from endolmphatic sac located under the dura in the posterior part of the petrous temporal bone
What is the fluid between the bony and membranous labyrinth?
- similar in compostion ot CSF
- empties via cochlear aqueduct into subarachnoid space
Perilymph
What contains the sensory receptor cells?
Spiral organ of corti
What do the specialized cells in the macula of the utricle sense?
Linear acceleration in the horizontal plane
- forward and back
- left to right
What do the specialized cells in the macula of the saccule sense?
Linear acceleration in the vertical plane
- up-down movement
