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Hearing Anatomy |
Inner ear labyrinth |
The inner ear is derived from a pair of surface sensory placodes (otic placodes) in the head region. These placodes fold inwards forming a depression, then pinch off entirely from the surface forming a fluid-filled sac or vesicle (otic vesicle, otocyst). The vesicle sinks into the head mesenchyme some of which closely surrounds the otocyst forming the otic capsule. The otocyst finally lies close to the early developing hindbrain (rhombencephalon) and the developing vestibulo-cochlear-facial ganglion complex.
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| Stage 13 developing head, showing the paired otocysts | Stage 22 developing head, showing inner ear structures |
Page Links: Introduction | Some Recent Findings | Historic Inner Ear Images | Cochlear | stage 13/14 embryo | stage 22 embryo | stage 22 embryo highpower | Reading | Computer Activities | Species Comparison of Cochlea Structure | Science Lecture (2004) Slides | Conductive Hearing Loss | Development Timing | Development Overview | References | Glossary
Related Pages: Inner Ear | Middle Ear | Outer Ear | Central Pathway | Abnormalities | Stage 13/14 | Stage 22 | Stage 22 Selected | Molecular | Week 4 Placode Development || Head Notes | Face Notes | Neural Notes
Chen Z, Montcouquiol M, Calderon R, Jenkins NA, Copeland NG, Kelley MW, Noben-Trauth K. Jxc1/Sobp, encoding a nuclear zinc finger protein, is critical for cochlear growth, cell fate, and patterning of the organ of corti. J Neurosci. 2008 Jun 25;28(26):6633-41.
"In jc mutants, the cellular patterning of the organ of Corti is severely disrupted, exhibiting supernumerary hair cells at the apex, showing mirror-image duplications of tunnel of Corti and inner hair cells, and expressing ectopic vestibular-like hair cells within Kölliker's organ."
Romand R, Dolle P, Hashino E. Retinoid signaling in inner ear development. J Neurobiol. 2006 Jun;66(7):687-704.
Carey J, Amin N. Evolutionary changes in the cochlea and labyrinth: Solving the problem of sound transmission to the balance organs of the inner ear. Anat Rec A Discov Mol Cell Evol Biol. 2006 Apr;288(4):482-9.
"...the pars superior of the labyrinth (utricle and semicircular canals) has remained fairly constant throughout evolution, the pars inferior (saccule and other otolith, macular, and auditory end organs) has seen considerable change as many adaptations were made for the development of auditory function. Among these were a relatively rigid membranous labyrinth wall, a variably rigid otic capsule, immersion of the membranous labyrinth in perilymph, a perilymphatic duct to channel acoustic pressure changes away from the vestibular organs, and different operating frequencies for vestibular versus auditory epithelia."
Kiernan AE, Pelling AL, Leung KK, Tang AS, Bell DM, Tease C, Lovell-Badge R, Steel KP, Cheah KS. Sox2 is required for sensory organ development in the mammalian inner ear. Nature. 2005 Apr 21;434(7036):1031-5.
""Sensory hair cells and their associated non-sensory supporting cells in the inner ear are fundamental for hearing and balance. They arise from a common progenitor, but little is known about the molecular events specifying this cell lineage."
Barald KF, Kelley MW. From placode to polarization: new tunes in inner ear development. Development. 2004 Sep;131(17):4119-30. Review.
(More? References)
Historic images of inner ear development and histological structure of the adult cochlear.
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A2: Otocyst (R). Apex of otocyst (primordium of L endolymphatic sac). |
A3: Otocyst; surrounding mesenchyme = otic capsule. Note proximity of otocyst to wall of rhombencephalon. Superior glossopharyngeal ganglion. Vestibulo-cochlear-facial ganglion complex (R). Trigeminal ganglion (not in image excerpt). |
A4: Indentation in rostral margin of otocyst = primordium of utriculosaccular canal. Note alignment of superior cardinal vein (LS) in relation to the nerve trunks (XS). Trigeminal ganglion (not in image excerpt). Note variation in height of cells of L otocyst wall. Dorsal end of 1st pharyngeal arch and groove (not in image excerpt). |
A5: Facial ganglion (R). "Floor" of L otocyst. Note on R, the former position of the otocyst in relation to the 2nd pharyngeal arch. |
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B3: Rhombic lip (developing cerebellum). IVth ventricle. Trigeminal ganglion. Adenohypophysis. Sphenoid cartilage. |
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B4: Cochlear duct and temporal cartilage. Semicircular duct (ampulla on L). Precartilage of auricle (pinna), malleus (medial, L), Incus (lateral, L). |
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B5: Extemal auditory meatus. Auricle. Incus (dorsal). Malleus (ventral). Tubotympanic recess (auditory rube). Tensor tympani m. (L). Utricle. Semicircular ducts. Intemal auditory meatus (R), containing vestibular and spiral ganglia. Endolymphatic sac (L). Note proximity of sac to choroid plexus of 4th ventricle. |
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B6: External auditory meatus. Primordium of tympanic membrane (L). Manubrium of malleus(L). Basal turn of cochlea duct (L). Endolymphatic sac (R). Common crus (R). Junction of utricle and saccule (R). Meckel's cartilage. Stapes (R). Auditory tube. |
Stage 22 embryo human head (mouth at top). The selected regions of inner ear are shown at right and are indicated by the blue boxes.
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Section showing turns of the developing cochlea duct and the associated cranial ganglion (CN VIII) component of the future organ of Corti. Also shown is the cranial ganglion (CN VIII) vestibular component. Note that both ganglionic components sit within and pass through the opening of the internal auditory meatus. |
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The internal auditory meatus or internal acoustic meatus (IAM) is an anatomical canal in which CN VII and CN VIII ganglia reside and pass through to the brainstem. This bony canal lies between the posterior surface of the petrous pyramid and the bony labyrinth within the dense petrous bone. Clinically this canal is also the common site of acoustic neuromas.
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Both ganglionic components of CNVIII (spiral and vestibular) sit within and pass through the opening of the internal auditory meatus. |
Different species have a different number of "snail shell-like" coils associated with the mature cochlea.
Human - two and a half coil
Guinea Pig - three coil
Mouse - one and three-quarter coil
UNSW Embryology:
Introduction | Abnormalities | Stage 13/14 | Stage 22 | Stage 22 Selected | Inner Ear | Middle Ear | Outer Ear | Molecular
Science Lecture (2004) Slides:
These links are to PDF versions Hearing Development slides from the 2004 Science lecture series. The first link is 1 Slide / Page for Viewing only. The second link is 4 Slides / Page for Printing. These documents are also linked from the Class Notes page.
PDF: Lecture 05 Hearing - 1 Slide/Page for Viewing | Lecture 05 Hearing - 4 Slides/Page for Printing
Embryo Images Unit: Inner Ear
Week 3 - otic placode, otic vesicle
Week 5 - cochlear part of otic vesicle elongates (humans 2.5 turns)
Week 9 - Mesenchyme surrounding membranous labrynth (otic capsule) chondrifies
Week 12-16 - Capsule adjacent to membranous labrynth undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph
Week 16-24 - Centres of ossification appear in remaining cartilage of otic capsule form petrous portion of temporal bone. Continues to ossify to form mastoid process of temporal bone.
3rd Trimester - Vibration acoustically of maternal abdominal wall induces startle respone in fetus.
(These are Human embryonic timings, not clinical which is based on last menstral period +2 weeks)
Inner ear - epidermal otic placode at level of hindbrain.
Middle ear - cavity: 1st pharyngeal pouch, ossicles: mesenchyme 1st and 2nd pharyngeal arches.
Outer ear - external auditory meatus: 1st pharyngeal cleft, auricle: 6 hillocks 1st and 2nd pharyngeal arches.
Conductive - disease of outer and middle ear
Sensorineural - cochlear or central auditory pathway
Congenital sensorineural - hereditary or acquired (see recent reviews)
Hereditary - recessive- severe, dominant- mild, can be associated with abnormal pigmentation (hair and irises)
Acquired
Rubella (German measles), maternal infection during 2nd month of pregnancy, vaccination of young girls
Drugs - streptomycin, antibiotic, thalidomide
Endolymphatic sac tumors (ELSTs), also described as papillary cystadenoma of the vestibular aqueduct, can occur sporadically or associated with the autosomal-dominant von Hippel-Lindau (VHL) disease. VLH is due to a germ line mutation.
The tumor erodes the surrounding posterior petrous bone and eventually cause hearing loss.
References:
Lonser RR, Baggenstos M, Kim HJ, Butman JA, Vortmeyer AO. The vestibular aqueduct: site of origin of endolymphatic sac tumors. J Neurosurg. 2008 Apr;108(4):751-6.
Gläsker S, Lonser RR, Tran MG, Ikejiri B, Butman JA, Zeng W, Maxwell PH, Zhuang Z, Oldfield EH, Vortmeyer AO. Effects of VHL deficiency on endolymphatic duct and sac. Cancer Res. 2005 Dec 1;65(23):10847-53.
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OMIM ID |
Symbol |
Description |
Position |
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TIMM8A DFN1 |
deafness, X-linked 1, progressive |
Xq22 |
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DFN2 |
deafness, X-linked 2, perceptive, congenital |
Xq22 |
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DFN4 |
deafness, X-linked 4, congenital sensorineural |
Xp21.2 |
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DFNB9 |
deafness, autosomal recessive 9 |
2p23-p22 |
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DIAPH1 |
diaphanous (Drosophila, homolog) 1 |
5q31 |
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GJB2 |
gap junction protein, beta 2, 26kD (connexin 26) |
13q11-q12 |
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MYO7A |
myosin VIIA (Usher syndrome 1B (autosomal recessive, severe)) |
11q13.5 |
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POU4F3 |
POU domain, class 4, transcription factor 3 |
5q31 |
Deafness Dystonia Syndrome - (MTS/DFN-1) suggested that this is a mitochondrial disease caused by a defective mitochondrial protein import system TIMM8A (TRANSLOCASE OF INNER MITOCHONDRIAL MEMBRANE 8)
Molecular Normal Development
Sage C, Huang M, Vollrath MA, Brown MC, Hinds PW, Corey DP, Vetter DE, Chen ZY. Essential role of retinoblastoma protein in mammalian hair cell development and hearing. Proc Natl Acad Sci U S A. 2006 Apr 28;
"The retinoblastoma protein pRb is required for cell-cycle exit of embryonic mammalian hair cells but not for their early differentiation. However, its role in postnatal hair cells is unknown. ...This study reveals essential yet distinct roles of pRb in cochlear and vestibular hair cell maturation, function, and survival and suggests that transient block of pRb function in mature hair cells may lead to propagation of functional hair cells."
Jones JM, Montcouquiol M, Dabdoub A, Woods C, Kelley MW. Inhibitors of differentiation and DNA binding (Ids) regulate Math1 and hair cell formation during the development of the organ of Corti. J Neurosci. 2006 Jan 11;26(2):550-8.
(More? OMIM ATONAL)"Basic helix-loop-helix (bHLH) transcription factor Math1 (Mouse homolog of ATH1, also called Atoh1) is both necessary and sufficient for hair cell development in the mammalian cochlea. The bHLH-related inhibitors of differentiation and DNA binding (Id) proteins negatively regulate many bHLH transcription factors including Math1. Progenitor cells expressing Ids during the time of hair cell differentiation were inhibited from developing as hair cells. Role for Ids in the regulation of expression of Math1 and hair cell differentiation in the developing cochlea."
Reviews | Articles | Search NCBI Bookshelf | Search PubMed
Reviews
Fritzsch B, Beisel KW, Pauley S, Soukup G. Molecular evolution of the vertebrate mechanosensory cell and ear. Int J Dev Biol. 2007;51(6-7):663-78.
Rodriguez K, Shah RK, Kenna M. Anomalies of the middle and inner ear. Otolaryngol Clin North Am. 2007 Feb;40(1):81-96, vi.
Articles
Romand R, Dolle P, Hashino E. Retinoid signaling in inner ear development. J Neurobiol. 2006 Jun;66(7):687-704.
Chen Z, Montcouquiol M, Calderon R, Jenkins NA, Copeland NG, Kelley MW, Noben-Trauth K. Jxc1/Sobp, encoding a nuclear zinc finger protein, is critical for cochlear growth, cell fate, and patterning of the organ of corti. J Neurosci. 2008 Jun 25;28(26):6633-41.
Jones JM, Montcouquiol M, Dabdoub A, Woods C, Kelley MW. [See Related Articles] Inhibitors of differentiation and DNA binding (Ids) regulate Math1 and hair cell formation during the development of the organ of Corti. J Neurosci. 2006 Jan 11;26(2):550-8.
Mantela J, Jiang Z, Ylikoski J, Fritzsch B, Zacksenhaus E, Pirvola U. The retinoblastoma gene pathway regulates the postmitotic state of hair cells of the mouse inner ear. Development. 2005 May;132(10):2377-88. Epub 2005 Apr 20.
Kawamoto K, Ishimoto S, Minoda R, Brough DE, Raphael Y. [See Related Articles] Math1 gene transfer generates new cochlear hair cells in mature guinea pigs in vivo. J Neurosci. 2003 Jun 1;23(11):4395-400.
Zine A, de Ribaupierre F. [See Related Articles] Notch/Notch ligands and Math1 expression patterns in the organ of Corti of wild-type and Hes1 and Hes5 mutant mice. Hear Res. 2002 Aug;170(1-2):22-31.
Search PubMed: Search June 2008 "cochlear development" 3,438 reference articles of which 359 were reviews.
Search term = cochlear development | otic placode | inner ear development | Organ of Corti development |
Reviews Abnormal Development (1999) (More? List of 1999 Ear Development Reviews)
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
altricial animal - Term used to describe an animal born in a helpless state, with incomplete development of sensory systems at birth. For example rats and mice are born with incomplete development of visual and auditory systems. (More? Rat Development | Mouse Development | Other Embryos)
ampulla - Term used to describe an anatomical dilation of a tube or canal lumen. Anatomical description of the opening end of the uterine tube lying above the ovary and the enlarged initial segmeny of the semicircular canals of the inner ear vestibular system. (More? Inner Ear | Genital System - Female Uterus)
aneurism - (Greek, aneurysma = a widening, aneurysm) A term used to describe an abnormal widening of a vessel or anatomical tubal structure. (More? Blood Vessel)
aquaeductus vestibuli - see vestibular aqueduct
auditory neuropathy - (AN) abnormality of transmission of sound information to the brain.
atresia – narrowing, usually of an anatomical tube or cavity.
Autophagocytosis – (Greek, auto = self, phagy = eating, also called autophagy) a cell death mechanism that uses the cell’s own lysosomes to self digest.
Border cells - columnar cells within the organ of Corti on the medial portion of the basilar membrane.
canalis reuniens – (ductus reuniens, canaliculus reuniens, canalis reuniens, Hensen's canal, Hensen's duct, uniting canal, canalis reuniens of Hensen) short narrow canal connecting the cochlea duct to the saccule. (Victor Hensen, 1835-1924)
Chondrified – the developmental differentiation of cartilage from mesenchye, an embryonic connective tissue.
cristae ampullaris – located in the ampulla of the membranous semicircular canals a region with both supporting and hair cells. The hair cell cilia are embedded in the gelatinous cupula.
Claudius cells - (cells of Claudius) columnar cells with microvilli overlying the basilar membrane and extend from Hensen's cells to the spiral prominence. Barrier cells that lie external to the organ of corti in endolymph.
Cochlear sac – embryonic structure, which will form the coiled cochlear duct and contribute to the saccule.
cochlear aqueduct - a bony channel containing the fibrous periotic duct. It connects the basal turn of the cochlea perilymphatic space with the subarachnoid space of the posterior cranial cavity.
Cochlin - major constituent of the inner ear extracellular matrix.
Collagen type II - major constituent of the inner ear extracellular matrix.
Conductive loss - term used to describe one of the two major classes of hearing loss involving external and middle ear abnormalities (other form is Sensorineural loss).
Connexins - channel proteins of the gap junctions that allow rapid communication between adjacent cells. The two connexins Cx26 and Cx30 are the major proteins of cochlear gap junctions.
Connexin 26 - A strikingly high proportion (50%) of congenital bilateral nonsyndromic sensorineural deafness cases have been linked to mutations in the GJB2 coding for the connexin26 {Inoshita, 2008 #1880}
cupular deposits - basophilic material on the cupulae of the semicircular ducts, an postnatal ageing phenomenon seen in some vestibular labyrinth.
clinical weeks – taken from last menstrual period (LMP) and therefore approximately two weeks before fertilization occurs.
Deiters' cells
Discoidin domain receptor 1 - (DDR1) a tyrosine kinase receptor activated by native collagen, expressed in the basement membrane and with fibrillar collagens. Found in basal cells of the stria vascularis, type III fibrocytes, and cells lining the basilar membrane of the organ of Corti. {Meyer zum Gottesberge, 2008 #1877}
ductus utriculosaccularis -
endochondral ossification – the process of bone formation from a pre-existing cartilage template.
endolymphatic sac - inner ear structure that has anatomically both an intraosseous and extraosseous component. Th e sac has functions regulating endolymph that are both secretory and absorptive. Also the site of endolymphatic sac tumors either sporadical occurring or associated with the autosomal-dominant von Hippel-Lindau (VHL) disease, due to a germ line mutation.
embryological weeks - taken from the time of fertilization which typically occurs around the middle (day 14), or just after, of the typical 28 day menstrual cycle.
Emx2 - homeobox gene affecting middle ear and inner ear development. {Rhodes, 2003 #1918}
espins – calcium-resistant actin-bundling proteins enriched in hair cell stereocilia and sensory cell microvilli and spiral ganglion neurons (SGNs)
fenestra ovalis - (oval window) separates the tympanic cavity from the vestibule of the osseous labyrinth.
fenestra rotunda - (round window) separates the tympanic cavity from the scala tympani of the cochlea.
fetus – (foetus) term used to describe human development after the 8th week (10th clinical week, LPM) and covers the developmental periods of second and third trimester.
fibroblast growth factor 1 – (Fgf-1) a growth factor released from cochlea sensory epithelium which stimulates spiral ganglion neurite branching. {Aletsee, 2003 #1924}
fibroblast growth factor 8 – (Fgf-8) a growth factor released by inner hair cells which regulates pillar cell number, position and rate of development. {Jacques, 2007 #1956}
fibroblast growth factor receptor 3 - (Fgfr-3) a tyrosine kinase receptor with a role in the commitment, differentiation and position of pillar cells in the organ of corti {Mueller, 2002 #1928}
fundamental frequency – (natural frequency) the lowest frequency in a harmonic series, for the female voice this is about 225 Hz.
Helicotrema – term used to describe the cochlear apex.
Hes – (hairy and enhancer of split) family of factors, which has been shown to be a general negative regulator of neurogenesis {Zheng, 2000 #1936}.
Hillock – a small hill, used to describe the six surface elevations on pharyngeal arch one and two.
Hindbrain –
Invaginate -
inner phalangeal cells
inner pillar cells – organ of Corti cells arranged in rows and form a boundary between the single row of inner hair cells and three rows of outer hair cells. These cells have surface-associated microtubule bundles {Henderson, 1995 #1950}.
inner sulcus - area of the cochlear duct
interdental region -
internal auditory meatus - (internal acoustic meatus, IAM) Anatomical canal in which CN VII and CN VIII ganglia reside and pass through to the brainstem. This bony canal lies between the posterior surface of the petrous pyramid and the bony labyrinth within the dense petrous bone. Also associated clinically with the site where acoustic neuromas may occur. (More? Hearing Development - Inner Ear)
Kölliker's organ - (Köllicker’s organ, greater epithelial ridge) Developing cochlear structure consisting of columnar-shaped supporting cells filling the inner sulcus and lying directly under the tectorial membrane. This transient organ regresses and generates the space of the inner sulcus. Rudolph Albert von Kolliker (1817-1905)??
lateral semicircular duct -
Limbus –
LMP – acronym for last menstrual period, used to clinically measure gestation.
mastoid process - of temporal bone
Math1 - homolog of the Drosophila proneural gene atonal, necessary and sufficient for the production of hair cells in the mouse inner ear. {Chen, 2002 #1932} Negatively regulated by Hes1 and Hes5
meatus – anatomical opening, cavity or space (external acoustic meatus,
internal auditory meatus)
Mucopolysaccharidosis - (MPS IIIB, Sanfilippo Syndrome type B) abnormality caused by a deficiency in the lysosomal enzyme N-acetyl-glucosaminidase (Naglu). Children with MPS IIIB develop abnormal hearing, and mental functioning culminating in early death.
Netrin-1 – secreted growth factor, expressed in the organ of Corti and spiral ganglion cells, role in process outgrowth.
neural tube –
olivocochlear – brainstem cholinergic and GABAergic efferent system that innervates sensory cells and sensory neurons of the inner ear.
organ of Corti –
organ of Corti protein II - (OCP-II) cytosolic protein or transcription factor?
otolithic membrane - extracellular matrix that cover the sensory epithelia of the inner ear.
ossify –
otic capsule –
otic cup
otic placode –
otic vesicle –
Otoconin - inner ear biominerals required for vestibular apparatus function.
Otogelin – (Otog) an inner ear specific glycoprotein expressed in cochlea cells at different developmental times.
otolithic membrane – a membrane within the utricle and saccule containing embedded hair cell cilia and small crystalline bodies of calcium carbonate (otoliths). Functions to detect head motion.
Otoliths - small crystalline bodies of calcium carbonate found within the otolitic membrane of the utricle and saccule.
Ototoxic – compound or drug causing temporary or permanent hearing loss.
Outer hair cells – (OHCs) three rows of hair cells that function to increase basilar membrane motion through a local mechanical feedback process within the cochlea, the “cochlear amplifier”.
outer pillar cells - arranged in rows and form a boundary between the single row of inner hair cells and three rows of outer hair cells.
perilymph –
perilymphatic space –
Periotic Capsule -
petrous portion - of temporal bone
pejvakin gene - in humans, two missense mutations in this gene cause nonsyndromic recessive deafness (DFNB59) by affecting the function of auditory neurons. {Schwander, 2007 #1883}
pharyngeal arch
pharyngeal pouch
pharyngeal membrane
Pharynx
Pillar cells – (PC) form an inner and outer row of support cells that form a boundary between inner and outer hair cells.
Placode
presbyacusis
Prestin – a motor protein structurally similar to the anion transporter family expressed in cochlear outer hair cells.
Primordium-
protocadherin 15 - (Pcdh15) required for initial formation of stereocilia bundles and changes in the actin meshwork within hair cells. The Ames waltzer (av) mouse mutant has both auditory and vestibular abnormalities from a mutation in this gene.
Reissner's membrane - (vestibular membrane, vestibular wall) is a membrane located inside the cochlea separating the scala media from scala vestibuli. Named after Ernst Reissner (1824-1878) a German anatomist. “It primarily functions as a diffusion barrier, allowing nutrients to travel from the perilymph to the endolymph of the membranous labyrinth.”
Rhombomere -
Saccular macula -
Saccule – (Latin, sacculus = a small pouch)
sacculocollic reflex –
scala tympani – one of the three Cochlea cavities, it is filled with perilymph.
Scarpa's ganglion – (vestibular ganglion) primary afferent vestibular neuron ganglion of the vestibular nerve. Located within the internal auditory meatus.
semicircular canals – series of fluid-filled loops of the inner ear required for balance and sensing acceleration.
sensorineural – term used to describe one of the two major classes of hearing loss involving the central pathway from the cochlear (other form is conductive loss).
space of Nuel – within the cochlea, an organ of Corti space between the outer pillar cells and the phalangeal and hair cells. Named after Jean-Pierre Nuel (1847-1920) a Belgian ophthalmologist.
spiral ganglion neurons - (SGN) innervate the inner (Type I) and outer (Type II) hair cells of the cochlea.
stapes – (stirrup) a middle ear auditory ossicle (bone).
stapes footplate -
startle response -
stereocilia –finger-like projections from the apical surface of sensory hair cells forming the hair bundle in the cochlea. Formed by tightly cross-linked parallel actin filaments in a paracrystalline array with cell surface specializations (tip links, horizontal top connectors, and tectorial membrane attachment crowns).
stria vascularis – forms the outer wall of the cochlear duct of the mammalian cochlea is composed primarily of three types of cells. Marginal cells line the lumen of the cochlear duct and are of epithelial origin. Basal cells also form a continuous layer and they may be mesodermal or derived from the neural crest. Intermediate cells are melanocyte-like cells, presumably derived from the neural crest, and are scattered between the marginal and basal cell layers. The stria forms endolymph and also contains a rich supply of blood vessels. (2612372)
sulcus –
synostotically – anatomically normally separate skeletal bones fused together.
tectorial membrane - extracellular matrix that cover the sensory epithelial hair cells of the organ of corti within the cochlea.
alpha-tectorin and beta- (TECTA, TECTB) major non-collagenous protein component of the tectorial membrane forming a striated-sheet matrix. Synthesized as glycosylphosphatidylinositol-linked, membrane bound precursors {Legan, 1997 #1865}
temporal bone –
teratogens–
trilaminar embryo -
tonotopy – term describing the mapping along the tectorial membrane within the cochlea of the different sound frequencies.
Utricle -
Vacuolization –
Vesicle –
vestibular apparatus –
vestibular evoked myogenic potential (VEMP) test
vestibular ganglion - (Scarpa's ganglion) primary afferent vestibular neuron ganglion of the vestibular nerve. Located within the internal auditory meatus.
vestibular membrane - (Reissner’s) extends from the spiral lamina to the outer wall and divides the cochlea into an upper scala vestibuli, a lower scala tympani.
Vestibulocochlear Nerve - Cranial Nerve VIII
Whirlin - A PDZ scaffold protein expressed in hair cells at the stereocilia tips, essential for the stereocilia elongation process. The DFNB31 gene mutations cause hearing loss in human and mouse. This protein can interact with membrane-associated guanylate kinase (MAGUK) protein, erythrocyte protein p55 (p55).
Wnt7a – signaling through the Wnt pathway regulates the development of hair cell unidirectional stereociliary bundle orientation.
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This page introduces the development of the inner ear from the simple otic placode structure through to the complex membranous labyrinth and associated cranial ganglion (CN VIII).
Look first at the early and late embryonic stage images of structures associated with this system (clicking on the small extracted image will show the entire embryo section).
There is another page covering Hearing Abnormalities.
Please email Dr Mark Hill if you wish to make a comment about this current project.
