Lec 8 Flashcards
Location of ear
All bodies in petrous part of temporal bone
Parts of the ear
External: auricle (elastic cartilage) Ext auditory meatus (canal of conducting sound) Pinna (tympanic portion filled with Cerumen/ear wax)
Mid: tympanic cavity
Inner: membranous labyrinth and bony labyrinth
Describe the tympanic membrane
1cm in diameter, fibrous sheath covered in both sides by epithelium. Innervated by auricotemporal, glossopharyngeal, vagus.
Make incision on ant inf quadrant outlined by cone of light, chorda tympani comes down from temporal tympanic cavity to jaw with lingual nerve to 3rd mand molar. If dmg - tongue affected
Middle ear - tympanic cavity walls
Roof (Tegmental wall) - tegment tympani
Floor (jugular wall) - thin plate above jugular bulb
Ant (carotid wall) - Carotid canal, pharyngotympanic tube, tensor tympani
Post (mastoid wall) - aditus into mastoid antrum
Lat (membranous wall) - tympanic membrane, epitympanic recess, chorda tympani, tensor tympani
Medial (Labyrinth wall) - promontory formed by basal turn of cochlea
What are the important structures of the lateral wall
Chorda tympani from CN7 passes on superior side
What are the important structures on medial wall
Basal turn of cochlea forms prominence which lies the tympanic plexus of CN9 (location of tympanic nerve to lesser petrosal nerve transition) This is the pathway of otic ganglion in infretemporal fossa to parotid gland
Pharyngotympanic tube of Eustace
mid ear tube to nasopahrynx anteromedially, functions to equalize pressure btwn the mid ear and atmospheric. Closed by muscles in adults. If microorganisms transverse it - otitis media. Regulated by contraction of tensor veli palatini, levater veli palatini and salpingopharyngeas
What are the bones of the mid ear and problems
malleus, incus, stapes
no periosteum so no osteogenesis
Describe the malleus
Has head, neck, 3 processes, handle realtes to chorda tympani, manubrium attached to tympanic membrane
Describe the incus
2 processes, articulates with other 2
Describe the Stapes
head, neck, 2 arms. Basal plate via oval window enabling direct contact with perilymph of inner ear
What are the muscles of the Tympanium
- Tensor tympani - attaches to handle of malleus (draws medially and tenses TM) M- medial pterygoid (V3). Acts to stablize inner ear and drum in loud noises
- Stapedius - prevents excessive mvmt of stapes, innervated by facial nerve
What are the 3 bony labyrinths
Semicircular, Vestibular, Cochlear. Filled with Perilymph
What are the membranous ducts and sacs
contains sense hair cells which are mechanoreceptors using sterocilia. Activates CN8
Organ of Corti also has hair calls and are innervated by cochlear nerve
What are the innervations of the auricle/Pinna
Auricotemporal - ant to EAM
Branches of 7 and 10 for opening of EAM
Greater auricular from C2,3
