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Eckel Ear CN VIII

QuestionAnswer
What is the Auricle of the ear (Pinna) Main structure of the external ear. Elastic cartilage covered by skin.
Aterial supply of Auricle Superficial Temporal A, Posterior Auricular A.
Main innervations of the Auricle 1.Auriculotemporal(CN V3) (Ant auricle/ ext aud meatus). 2.Greater Auricular(Post root C2,3) (Inf auricle). 3.Posterior Auricular(CN VII)(Posterior half of Auricle: Antitragus, Antihelix, Helix). 4.CN X (contributes to ext aud meatus). 5.Lesser Occipi
Why is the tympanic membrane more susceptable to damage in infants versus adults? Their external auditory meatus is relatively short. **Pull infants ear inferoposterior during exam, posterosuperiorly for adults**
Stapedius M Goes from Stapes bone to posterior wall. Innervated by CN VII N to Stapedius.
What 3 bones connect the tympanic membrane to the oval window within the middle ear. (In order) 1.Malleus. 2.Incus. 3.Stapes (hits the oval window and causes movement of fluid in inner ear). **Amplify the sound waves hitting the tympanic membrane. (MAIN FUNCTION)
Innervation of the Tympanic Membrane External Surface: Auriculotymporal N (CN V3) and CN X auricular branch. Internal Surface: Tympanic plexus (CN IX)
What bone does the middle ear lie in? Petrous part of the Temporal Bone
Tensor Tympani M Muscle inserts on to the Malleus. Innervated by CN V3.
Function of both Tensor Tympani (CN V3) and Stapedius (CN VII) Dampen the oscillations of the middle ear bones in response to loud sounds (this protects against damage to the hair cells within the inner ear)
Affect on Middle ear due to Injury to the facial N (CN VII) Hyperacusis. You will have no dampening effect so you will hear the really loud sound
Where does the Chondra Tympani arise? From CN VII before the stylomastoid foramen. Then passes over the tympanic membrane and through the middle ear cavity and jumps on the Lingual N (V3)
Auditory Tube (Eustacian Tube) connects what? What innervates it? Nasopharynx and the middle ear cavity. Innervted by branches of the tympanic plexus (CN IX) **Allows for spread of infection**
Why are children more prone to ear infections B/c the auditory (Eustacian) tube tends to be more horizontally placed and the ostium is patent which allows infection easier access from the nasopharynx to the middle ear.
What helps regulate the change in pressure felt within the middle ear as altitude changes? Auditory (Eustacian) Tube. Equalizes the pressure between the middle and Ext ear so that sound isn't affected.
Mastoid Air Cells Like sinuses. Opening into them is the Mastoid Antrum. Infections in the middle ear can pass into here.
What is the smallest bone in the human body Stapes
Otitis Media Middle ear infection usually secondary to a upper respiratory infection. The tympanic membrane will be red and bulging. (CN IX is at risk.) (Also could spread to the mastoid air cells via mastoid antrum: MASTOIDITIS)
***KNOW HOW TO ID MASTOID AIR CELLS FOR PRACTICAL***
Lesion on CN VIII Loss of hearing, Dizziness, could also affect chorda tympani
What fluid and structures are located in the Bony Labyrinth? (inner ear) Perilymph fluid. Structures: Cochlea, Vestibule, and semicircular canals. **In the Otic capsule within the petrous part of the temporal bone.
What fluid and structures are located in the Membranous Labyrinth? (inner ear) Endolymph fluid. Structures: (contains the special sensory receptors) cochlear duct, utricle, saccule, and semicircular ducts
Contents and function of the vestibule of the boney labyrinth? Utricle and Saccule (membranous labyrinth) which contain the Macula (special sensory region). FUNCTION: Equilibrium sensor for LINEAR acceleration via otoliths and hair cells attached to vestibular branches of CN VIII
Contents and function of the Semicircular canals of the boney labyrinth? Semicircular Ducts (membranous labyrinth) which contain Cristae Ampullares (special sensory region). FUNCTION: Equilibrium sensor for ANGULAR acceleration via hair cells attached to Vestibular Branch of CN VIII
Contents and function of the Cochlea of the boney labyrinth? Cochlear Duct (membranous labyrinth) which contains the Sprial Organ (special sensory region). FUNCTION: Hearing via tectorial membrane and hair cells attached to cochlear branch of CN VIII
What casuses the action potential transmission form the ear to the pons via CN VIII? Bending of the Hair cells associated with either the vestibular or cochlear branch of CN VIII
Whats causes perilymph waves in the vestibule of the inner ear? Stapes tapping on the ovale window (beginning of fluid wave in the cochlea)
Track the movement of perilymph waves within the cochlea 1.Oval window, 2.Vestibule, 3.Scala vestibuli, 4.Apex of cochlea. 5.Scala tympani, 6.Round window (secondary tympanic membrane).
What is the importance of the Round windonw (Secondary tympanic membrane)? It allows the energery, initially recieved by the oval window and transmitted as perilymph fluid waves, to dissipate back into the middle ear (tympanic cavity)
Floor and Roof of the cochlear duct ROOF: Vesibular membrane (seperating the Scala vestibuli). FLOOR: Basilar membrane (seperating the scala tympani).
Mechanism behind the Spiral organ It is situated on the basilar membrane and is overlaid by the gelatinous tectorial membrane. The BASILAR membrane is the one that moves inducing hair bending
Created by: WeeG