Inner Ear Flashcards
Cochlea x1
derived from “shell” base and apex
osseous spiral cochlear canal
ossesous labyrinth part of this structure
osseous spiral lamina
thin delicate bone, not solid inside is where neurons run to and from hair cells
Basilar Membrane
connective tissue has cells that vibrates when stimulate ear with sound –> runs from base to apex
modiolus
honey combed with air cells, provides support for other structures
Reissner’s Membrane
epithelium (2 cell thick) layer dividing each turn into 3 spaces
Cochlear Duct
structure that defines space inside (scala media) membranous labyrinth of cochlea 3 boundaries are: basilar membrane, stria vascularis, reissner’s membrane separates scala tympani and scala vestibuli (except at apex)
Scala tympani
ends in dead end except for round window, (secondary tympanic membrane)
Helicotrema
apex of cochlear duct where scala tympani and scala vestibuli meet, joining of 2 sections
stria vascularis
anchored to wall by spiral ligament, tissue just inside it rich capillary bed with a lot of bloody supply to entire inner ear –>generates endolymph
spiral ganglion
cell bodies of this reside in sensory neurons of ear
organ of corti
organ of hearing, attached to spiral limbus (sits on top of spiral lamina)
spiral limbus
secretes cells of tectorial membrane
Cochlear Duct Cells
Top of Organ of Corti: Hinson Cells, microvill are top tiny rods extending Tight Junctions
Tight Junctions
tight: glue with insulating properties, proteins in the membranes that connect one cell together very tightly –> tighter the junctions the harder it is for ionic compounds to cross over (keeps endolymph and perilymph apart from another)
Reissner’s membrane (cell)
2 cells thick epithelium 1-mesothelial cell layer –> whispy matrix between 2 called basement membrane 2-endothelial cell layer -> tight junctions, microvilli facing scala media, many cell organelles
Basilar Membrane Zones
Arcuate Zone Pectinate Zone
Arcuate Zone
has 1 layer of fibrous bands has thinner base membrane moves as unit because of it’s structure
Pectinate Zone
what tapers most in mechanical properities thicker than arcuate zone base membrane fibrous layer: connective tissue with denser bands –> homogenous layer and fibrous bands (2 in pectinate)
Stria Vascularis Cells
Blood capillaries run in it, marginal cells: face endolymph, filled with mitochondria in feet (ATP) –> transport ions sodium out onto feet, K+ by smooth side –>has positive voltage inside bc much movement of K+ into cells, electrogenic pumping
Tectorial Membrane Zones
Limbal Zone Middle Zone Marginal Band
Limbal Zone
attachment to spiral limbus -intersulcus cells-line space under tectorial membrane close to modialis space in organ of corti -inner spiral cells: covered by limbal zone-one end tectorial membrane attached to limbus
Middle Zone
distinguished by broad thick fibrous region
Marginal Band
loosely attachment with organ of corti Not as stationary as limbal zone, free to move as basilar membrane moves up and down Kimura’s membrane & hensen’s stripe
Kimura’s membrane
specifically attaches to OHC (firm attachment) in marginal band of tectorial membrane
Hensen’s Stripe
lies over IHC but does not come into contact with stereocilia
Organ of Corti Cells
Pillar Cells Deiter Cells Hensen Cells inner sulcus cells
pillar cells
have feet, head and stalks-in pairs lock together Tunnel of corti between 2 pillar cells with perilymph, top surface of organ of corti Head: tightly attached at this point, contains structural actin Stalk: tonofilaments (tubulin and actin) -provide support for hair cells Feet: sit on basilar membrane and are attached, structural actin
Deiter Cell
Base is rigid structure with room for neurons to make synapses, touches tip of pillar cell, tight junctions form, ABLE to contract 3 rows of deiter cells Spaces of Neul=perilymph in space between OHC and deiter cell has phalangeal process Deiter’s Cup: have network of tonofilaments in base, OHC sit in here (all 3 rows) Body
Hensen Cells
tight junctions between all of it, maintains perilymph endolymph boundary
Reticular Lamina
top of organ of corti from inner hair cell to lateral outer hair cell
Outer Hair Cells
cylindrical: suggests analogy with vestibular type 2 cells vary in length: longer in apex and steadily get shorter to the base, directly underneath kimura’s membrane
Outer Hair cell zones
Receptor Pole Subcuticular Zone Supranuclear Zone Nucleus Synaptic Zone
Receptor Pole (OHC)
Cuticular plate that stereocilia attach to zone of OHC, transduction occurs here, stereocilia in W shape, tip links are site of transduction, attachment of tallest OHC stereocilia to tectorial membrane stereocilia have rigid structure and tapers to end, end goes into cuticular plate and forms nice connection and weak point is at base
Subcuticular Zone (OHC)
lysosomes, mitochondria, Hensen bodies (Ca metabolism –>controls transduction)
Supranuclear Zone (OHC)
laminated cisternae (inside OHC), prestin (in cell membrane)
Synaptic Zone (OHC)
efferent and afferent nerve terminals on soma
efferent: regulate gain of cochlear amplifier –> modulate sensitivity of ear to sounds at certain conditions, has subsynaptic sister (stores calcium to release as NT are released) (radial efferent)
spiral afferent
OHC Innervation
Type A: primarly efferent innervation (predominant in base)
Type B: primarily afferent innervation (prominent in apex)
IHC
Don’t have prestin in membrane (don’t know if help with amplification)
Primarily signaling pathway for brain, have healthy afferent pattern
Primary information conduct to CNS
decoupled for low frequency vibrations, but as frequency increases and shearing increases, coupling is effective at higher frequencies
IHC=high pass filter
Receptor Pole (IHC)
stereocilia not attached to tectorial membrane, underneath cuticular plate: Golgi Zone (abundance of golgi apparatus)
Subnuclear Zone
Rough endoplasmic reticulum ribosomes: synthesize proteins that are part of synaptic system/machinery very profilerated (Golgi + ER) --\> like in neurons
Synaptic Zone (IHC)
Many small afferent terminals neurons
fundamental for hearing, especially temporal unique to hearing
Reticular Lamina
Especially in OHC, this is speculated to lead to HC degeneration
holes in reticular lamina result in mixing of endolymph and perilymph
endolymph enters fluid space of organ of corti
supporting cell processes enlarge and close holes (rapidly) to form tight junctions between them –> allow surviving cells to function
Wipeout of Organ of Corti
Myelinated neural fibers due to noise exposure –> region of organ of corti gave “dead cone” left to seal boundary MNF’s wiped out
