Auditory System Anatomy Flashcards
Divisions
-Outer: pinna-TM
-Middle: TM-Oval window
-Inner: oval window-internal auditory meatus
-Central: internal auditory meatus-auditory cortex
Outer Ear
-Pinna (auricle)
-helix
-antihelix
-scaphoid fossa
-triangular fossa
-tragus
-antitragus
-concha
-lobule
External Auditory Meatus (EAM)
-“S” shaped
-28mm long
-7mm diameter
External Auditory Meatus (EAM): Outer 1/3
Cartilage
Courses medially and up
External Auditory Meatus (EAM): Inner 2/3
Cartilage
Courses down and medially
External Auditory Meatus (EAM): Hairs
-cartilaginous portion/outer 1/3
External Auditory Meatus (EAM): Cerumen Gland
-cartilaginous portion/outer 1/3
TM Divisions
-Pars flaccida: upper 1/3
-Pars Tensa: upper 2/3
-Notch of rivinus: allows radial fibers to attach
TM Layers
-Epithelial tissue: continuous w/EAM
-Mucosa: continuous w/middle ear lining
-Radial Fibers: in pars tensa, fibers attcahed to notch of rivinus
Healthy TM Appearance
-pearly
-grey
-translucent
-concave: sucked into middle ear
Direction of Malleus Determines Left or Right Ear: Left
-malleus points to 10-11 oclock
Direction of Malleus Determines Left or Right Ear: Right
-malleus points to 1-2 oclock
Middle Ear
-oval or egg shaped\
-6 walls
Middle Ear Lateral Wall
-membranous wall
-TM
Middle Ear Anterior Wall
-carotid wall: carotid artery in front of wall
-eustachian tube opening
Middle Ear Posterior Wall
-mastoid wall: mastoid bone under wall
-aditus: opening off posterior wall
-pyramidal eminence
Middle Ear Inferior Wall
-jugular wall: jugular vein underneath wall
Middle Ear Superior Wall
-tegmental wall made up of tegmental bone
Middle Ear Medial Wall
-labyrinthine wall
-fenestra vestibuli: oval window
-fenestra cochlea/rotunda: round window
-promontory: basal turn of cochlea that can’t fit in cochlea so juts out
Malleus Landmarks
-Head
-Neck
-Lateral process
-Manubrium
-Umbo
-Connection to Incus
-attaches to TM along length of manubrium
-malleus head: bulk of bone
-head articulates with body of incus
-head of malleus and body of incus in epitympanic recess
Incus Landmarks
-Short process
-Long process
-Lenticular process
-Connection to malleus
-Connection to stapes
-short process projects posteriorly
-long process bends medially: has lenticular process where stapes articulates at
Stapes Landmarks
-Connection to Incus
-Head
-Neck
-Anterior Crus
-Posterior Crus: thinnest part
-Footplate
-Stapes head articulates w/incus
-Stapes footplate sits in oval window which keeps fluid in cochlea
Ligaments
-hold ossicles in place
-allow relatively free movement
Stapedial Muscle: Originates
-posterior wall
-tiny hole top pyramidal eminence
Stapedial Muscle: attaches
-posterior portion stapes neck
Stapedial Muscle: innervation
CN VII (Facial)
Stapedial Muscle: Contraction
stapes moves and tenses oval window
pyramidal wall stationary
Tensor Tympani: Originates
-anterior wall
-area called semi canal of tensor tympani
-above eustachian tube opening
Tensor Tympani: Attaches
-manubrium of malleus
Tensor Tympani: innervation
CN V (Trigeminal)
Tensor Tympani: Contraction
-pulls malleus and tightens TM
Tensor Tympani & Stapedial
-Placed: antagonists (push against each other)
-Work: synergists
Eustachian Tube
-Connects middle ear to pharyngeal wall
-equalizes pressure in ME
Eustachian Tube Divisions
-osseous
-cartilaginous
-membranous
-isthmus: muscles
Eustachian Tube Length
-adult: 35-38 mm
-child: 1/2 adult, 12-16mm
Eustachian Tube Angle
-adult: 35-45 degree
-child: more horizontal
Inner Ear Divisions
-Auditory
-Vestibular
Vestibular System: Consists of peripheral sensory apparatus
-6 semicircular canals
-4 otoliths
Vestibular System: Central Processor
-vestibular nuclei
-cerebellum
Vestibular System: Mechanism for motor output
-including reflexes
-vestibulo-ocular reflex
Semicircular Canal
-Fluid filled: endolymph
-same as scala media
-connects to auditory portion via ductus reuniens
-any 2 canals form right angle
-open into vestibule: cavity within inner ear, contains ampulla
Anterior Semicircular Canal
superior
Posterior Semicircular Canal
inferior
Lateral Semicircular Canal
-horizontal: 30 degree angle to horizontal plane
Ampulla
-Bulbous enlargements at end of each semicircular canal
-3 ampullae situated at different angles: contains sensory hair cells, detects rotations in all three planes of motion (horizontal, vertical, sagittal)
-contains crista and cupula
Ampulla Crista
-crest like septum perpendicular to longitudinal axis of canal
-cilia project into cupula
Ampulla Cupula
-sits on top of crista
-closes opening between semicircular canal and utricle
Otoliths: Utricle
-lies in oval shape area beneath semicircular canals
-cilia project and embed in gelatinous membrane
-otolithic membrane: macula, contains small calcium carbonate crystals called otoconia
-monitors horizontal movement (walking straight)`
Otoliths: Saccule
-lies in oval shape area beneath semicircular canals
-cilia project and embed in gelatinous membrane
-otolithic membrane: macula, contains small calcium carbonate crystals called otoconia
-monitors vertical movement (elevator)
-connects to cochlea via ductus reuniens (scala media)
Cochlear Openings: Round Window
opens into scala tympani
Cochlear Openings: Oval Window
-end of scala vestibuli
Cochlear Openings: Cochlear Aquaduct
-small bony channel within temporal bone connect subarachnoid space with scala tympani
Cochlear Openings: Ductus Reuniens
-AKA: canalis reuniens of Hensen
-small membranous duct connects lower part to saccule to scala media
Cochlea
-snail shaped
-coiled around Modiolus (support for cochlea): 2 1/4 -2 3/4
-base near vestibule
Modiolus
-Finely perforated bone: Cochlear core
- Neurons through perforations
Canals of Cochlea: Scala Vestibuli
-run oval window to apex of cochlea
-perilymph
-oval window closer to vestibular system
Cochlear Openings: Scala Tympani
-run apex cochlea to round window
-perilymph
-round window closer to TM
Cochlear Openings: Helicotrema
-small passage connects scala vestibuli and scala tympani
Cochlear Openings: Scala Media
-lies between scala vestibuli and scala tympani
-endolymph (brought by ductus reuniens)
-contains organ of corti
Osseous Spiral Lamina
-Thin bony shelf projects from modiolus: separates scala tympani and scala vestibuli
-gets progressively smaller as approach apex: allows basilar membrane to widen
-At apex: hook like communication with helicotrema
Cochlear Membranes
-Reissner’s: separates scala vestibuli from scala media
-Basilar: separates scala tympani form scale media, organ of corti sits on it
Scala Media Landmarks
-osseous spiral lamina
-stria vascularis: vascular supply
-Reissner’s membrane
-Basilar membrane
-Organ of Corti
Organ of Corti: Border Cells
-support
Organ of Corti: Inner Pharyngeal Cells
-support
Organ of Corti: Inner Hair Cells
-not embedded in techtorial membrane
Organ of Corti: Rods of Corti
-inner and outer
Organ of Corti: Tunnel of Corti
-between rods
-Organ of Corti: Tunnel of Nuel
-other side of rods
Cells of Deiter/Deiter Cups
`-tulips with outer hair cells sit inside them
Organ of Corti: Outer Hair Cells
-tallest embedded in techtorial membrane
Organ of Corti: Reticular Lamina
-holds outer hair cells in place
Organ of Corti: Hensen Cells
-larger than claudius
-support
Organ of Corti: Claudius Cells
-smaller than Hensen
-support
Techtorial Membrane
-dome on stadium
-only attached on one side
Cochlear Hair Cells: Inner
-straight line pattern
-tear drop shape
Cochlear Hair Cells: Outer
-soft “w” pattern
-cylinder shape
-embed in techtorial membrane
-3 cilia per cell
Cochlear Hair Cells: Inner and Outer Hair Cells
-cilia connected by tip links
-thin filaments connect tips
Hair Cell Innervation: Afferent Innervation Type 1 Fibers
-myelinated (efficient)
-each inner hair cell connected by 10-20 VIII nerve fibers
-95% of auditory (aud portion of VIII nerve)
-1 IHC connected to 10+ nerves
Hair Cell Innervation: Afferent Innervation Type 2 Fibers
-unmyelinated
-connect to outer hair cells
-each outer hair cell shares innervation with over 10 other outer hair cells
-1 nerve connected to at least 10 OHC
Hair Cell Innervation: Efferent Innervation
-olivocochlear bundle
Hair Cell Innervation: Efferent Innervation from superior olivary complex to cochlea
-activated by cortex
-inhibitory function]
-reduces activity of hair cells
-crossed olivocochlear bundle inhibit outer hair cells: contralateral
-uncrossed olivocochlear bundle inhibit inner hair cells: ipsilateral
-help with signal to noise ratio
After Cochlea
-exit cochlear via modiolus
-pass through internal auditory meatus: enters the central auditory nervous system
Central Auditory Pathway
-cochlear nuclei (bottom structure)
-superior olivary complex
-lateral lemniscus
-inferior colliculus
-medial geniculate body (last location in brainstem)
-auditory cortex (temporal bone, top structure)
-somewhere past cochlear nuclei 60-75% of neurons end up on contralateral side
