Anatomy And Histology Of Ear Flashcards
External Ear blood supply
Posterior Auricular a and superficial temporal artery
What part of ear does facial n innervate?
Pinna and inside rim of pinna
Auriculotemporal n innervated what part of ear?
Front part, but not external acoustic meatus
What innervates the external accoustic meatus?
Vagus and glossopharyngeal n
What are the four parts of the tympanic membrane innervated by?
Superior: VII
Posterior: Great Auricular n
Inferior: Arnold n
Anterior: auriculotemporal
Cough reflex of ear?
Afferent: Vagus
Efferent: Vagus and phrenic
What is important about internal 1/3 of external accoustic meatus?
It’s the only place in body where skin overlaps bone
-site of bleeding
From histo, how do you know if you’re in inner part of outer part of external acoustic meatus?
Outer ear: hair cells, sebaceous glands, sweat glands, connective tissue
Inner ear: basically skin over bone
Walls of Middle Ear
Roof: Trigeminal Cavity
Floor: Jugular wall—jugular bulb behind from Sagittal sinus
Lateral: Membranous Wall-tympanic membrane
Medial: Labyrinthine Wall—semicircular canals and cochlea
Posterior: mastoid wall—mastoid process
Anterior: ICA
Tympanic Membrane
Cone is oriented toward external acoustic meatus
-tip of malleus called umbo
Has a flaccid and tense part
What is the function of the pharyngotympanic tube?`
Equalize pressure
What muscles elevate the pharyngotympanic tube?
Levator Veli Palatini: CNX
Tensor Veli Palatini: CNV
Pharyngotympanic Tube Histology
Pseudostratefied Epithelium (part of pharynx, remember?
Can see seromucus gland
Tensor Tympani Muscle
Origin, Insertion, Innervation, Action
OI: surface of pharyngotympanic tube to handle of malleolus
Innervation: CNV
Action: Pulls on handle to tense membrane and reduce amplitude
Stapedius M
Origin, Insertion, Innervation, Action
OI: pyramidial eminence to neck of stapes bone
Innervation: Facial CNVII
Action: reduce amplitude of stapes to reduce amount of sound transferred
Bony labyrinth
Within petrous region of temporal bone; line with endosteum has membranous labyrinth within, separated by perilymph
Membranous Labryrinth
Made of small sacs and tubes within bony labyrinth
Two different sections for different jobs
- Cochlear Duct: hearing
- Utricle, Saccule, Semicircular ducts: balance
Hair cells
Kinocillium with stereocillia next to it
- if otocilia move in the direction towards kinocillium=depolarization
- if otocilia move in direction away from kinocillium=polarization
Cochlea Mechanism
Oval window vibrates due to ossicles
Perilymph in scale vestibuli makes wave and crashes into vestibular membrane of scala media
Endolymph in scala media makes wave, crashes into basilar membrane of scala tympani
-endolymph also hits the tectorial membrane of organ of corti
Organ of Corti
Hair cells embedded in tectoral membrane which extends from spiral lamina
-deflection of stereocilia depolarizers channels of hair cells
Bipolar neuron cell bodies located in spiral ganglion are within what?
Modiolus=central axis
Middle Ear function
Transmit vibrations and depressurization via pharyngotympanic tube
Inner Ear: Balance Semicircular canals
Semicircular Canals w ampulla
-three canals w different axis filled with endolymph
Ampulla have cap called cupulla, which is what is displaced by fluid motion in canal
-rotational velocity
Inner Ear Balance: Utricle and Saccule
Vestibule contains saccule and utricle
-each contains a macula w cluster of hair cells displaced by otoconia
For linear acceleration and gravity
What is utricle for?
Linear acceleration and tilts head in horizontal plane
-U trip forward
What is the saccule for?
Linear acceleration and head tilts in vertical plane
-u suck up
Perilymph
Similar to CSF
-drains via perilymphic duct into subarachoid space
—why infections can spread from inner ear to brain
Endolymph
Within membranous labyrinth and scala media
-scala vascularis makes it
—drains via endolymphatic duct into venous sinuses of dura mater
How does cauliflower ear happen?
Ear is made of elastic cartilage
- when damaged, chondrogenesis of perichondrium happens
- causes thickening of ear
Mastoiditis
Infection of mastoid cells
-can spread to cranial fossa via petrosqamous crania suture
—can spread into sigmoid sinus
Tympanic Membrane damage
Medial ear pressure due to fluid
Most heal on own, but can be treated with antibiotics
—but not gentamicin!
Otitis Media
Ear ache with possible fluid or pus in middle ear due to inflammation
-untreated can cause scarring of ossicles
Why do little kids get otitis media more often?
Their pharyngotympanic tube is more horizontal, so fluid is more likely to build up there
Menieres syndrome
Dizziness, vertigo, tinnitus, and hearing loss
-due to increase endolymph
Viral labyrinthitis: symptoms and treatment
Dizziness, vertigo, tinnitus, and hearing loss
Treatment isn’t really anything; resolves within a week
