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Eckel Ear CN VIII
| Question | Answer |
|---|---|
| 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
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