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We use the sense of balance and hearing to position ourselves in space, sense our surrounding environment, and to communicate. Portions of the ear appear very early in development as specialized region (otic placode) on the embryo surface that sinks into the mesenchyme to form a vesicle (otic vesicle = otocyst) that form the inner ear. Further detailed notes covering specific topics are on linked pages. |
This region connects centrally to the nervous system and peripherally through specialized bones to the external ear (auricle). This organisation develops different sources forming the 3 ear parts: inner ear (otic placode, otocyst), middle ear (1st pharyngeal pouch and 1st and 2nd arch mesenchyme), and outer ear (1st pharyngeal cleft and 6 surface hillocks). This complex origin, organisation, and timecourse means that abnormal development of any one system can impact upon the development of hearing. |
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Look first at the early and late embryonic stage images of structures associated with this system. |
Page Links: Introduction | Some Recent Findings | Development Timing | Reading | Computer Activities | Objectives | Development Timing | Inner Ear | Middle Ear | Outer Ear | Development Overview | stage 13/14 embryo | stage 22 embryo | stage 22 embryo highpower | Science Lecture (2004) Slides | Congenital Deafness | Conductive Hearing Loss | References | Glossary | Terms
Related Pages: Inner Ear | Middle Ear | Outer Ear | Central Pathway | Abnormalities | Stage 13/14 | Stage 22 | Stage 22 Selected | Molecular
Werner LA. Issues in human auditory development. J Commun Disord. 2007 Mar 13;
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."
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.
Rowe TM, Rizzi M, Hirose K, Peters GA, Sen GC. A role of the double-stranded RNA-binding protein PACT in mouse ear development and hearing. Proc Natl Acad Sci U S A. 2006 Mar 29;
".. Pact(-/-) mouse were reduced size and severe microtia. As a result of the congenital abnormality of both outer and middle ears, these mice were hearing impaired. Our study demonstrated an essential role of PACT in mammalian ear development and produced the first animal model for studying human microtia."
For more articles see References.
UNSW Embryology: Stage 13/14 | Stage 22 | Stage 22 | Stage 22 Selected | Hearing Abnormalities | Following pages under development: Inner Ear | Middle Ear | Outer Ear | Molecular | Human Systems | Stage 22 Head Set | Stage 13/14 Head Set
Science Lecture: 2008 ANAT2341 Lecture 17 Hearing These documents are also linked from the Class Notes page.
PDF 2004 Slides: Lecture 05 Hearing, 1 Slide / Page for Viewing | Lecture 05 Hearing, 4 Slides / Page for Printing
Embryo Images Unit: Embryo Images Online | Ear Development | Inner Ear | Middle Ear | External Ear
Movies: Senses Movies
Week 3 - otic placode, otic vesicle
Week 5 - cochlear part of otic vesicle elongates (humans 2.5 turns)
Week 9 - Mesenchyme surrounding membranous labryinth (otic capsule) chondrifies
Week 12-16 - Capsule adjacent to membranous labryinth 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 response 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.
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There is a detailed notes page covering Inner Ear Development. 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. External Link: Embryo Images Unit - Inner Ear |
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There is a detailed notes page covering Middle Ear Development. The middle ear ossicles (bones) are derived from 1st and 2nd arch mesenchyme. The space in which these bones sit is derived from the 1st pharyngeal pouch. External Link: Embryo Images Unit - Middle Ear |
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There is a detailed notes page covering Outer Ear Development. The external ear is derived from 6 surface hillocks, 3 on each of pharyngeal arch 1 and 2. The external auditory meatus is derived from the 1st pharyngeal cleft. The newborn external ear structure and position is an easily accessible diagnostic tool for potential abnormalities or further clinical screening. External Link: Embryo Images Unit - External Ear |
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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). |
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. |
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. |
Regions of stage 22 embryo head (mouth at top) in selected images of inner ear below
Development of Hearing - 3 divisions of ear
- derived from first pharyngeal pouch
- extends as tubotympanic recess
- during week 5 recess contacts outer ear canal
- hereditary or acquired
- see recent reviews
(More? Hearing Abnormalities)
(More? Hearing Abnormalities)
Many of the links below are to external resources and require an internet connection.
Links: Earlier References | Journals | Online Textbooks | Search Textbooks | PubMed | Search PubMed | Books | Glossary
1999 and Earlier References: Neuralation | Notch Articles/Reviews | Sonic Hedgehog Articles/Reviews | Dorsal | Clinical | Folate |
Developmental Brain Research Content Listing
Neural Development Welcome to Neural Development | Pubmed Central Volume 1 2006 | Pubmed Central Volume 2 2007 |
International Journal for Developmental Neuroscience Official Journal of the International Society for Developmental Neuroscience |
Developmental Neuroscience Journal Homepage | Hippocampal Development | Vol. 29, No. 3, 2007 |
Neuroscience Official journal of The International Brain Research Organisation (IBRO)
Developmental Biology (6th ed) Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000. Evolution of the mammalian middle ear bones from the reptilian jaw | Chick embryo rhombomere neural crest cells | Some derivatives of the pharyngeal arches | Formation of the Neural Tube | Differentiation of the Neural Tube | Tissue Architecture of the Central Nervous System | Neuronal Types | Snapshot Summary: Central Nervous System and Epidermis
Neuroscience Purves, Dale; Augustine, George J.; Fitzpatrick, David; Katz, Lawrence C.; LaMantia, Anthony-Samuel; McNamara, James O.; Williams, S. Mark. Sunderland (MA): Sinauer Associates, Inc. ; c2001 The Auditory System | The Inner Ear | The Middle Ear | The External Ear | Early Brain Development | Construction of Neural Circuits | Modification of Brain Circuits as a Result of Experience
Molecular Biology of the Cell (4th Edn) Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter. New York: Garland Publishing; 2002. Neural Development | The three phases of neural development
Clinical Methods 63. Cranial Nerves IX and X: The Glossopharyngeal and Vagus Nerves | The Tongue | 126. The Ear and Auditory System | An Overview of the Head and Neck - Ears and Hearing | Audiometry
Health Services/Technology Assessment Text (HSTAT) Bethesda (MD): National Library of Medicine (US), 2003 Oct. Developmental Disorders Associated with Failure to Thrive
Eurekah Bioscience CollectionCranial Neural Crest and Development of the Head Skeleton
Search NLM Online Textbooks- "neural development" : Developmental Biology | The Cell- A molecular Approach | Molecular Biology of the Cell | Endocrinology
Reviews
Werner LA. Issues in human auditory development. J Commun Disord. 2007 Mar 13;
Barald KF, Kelley MW. From placode to polarization: new tunes in inner ear development. Development. 2004 Sep;131(17):4119-30. Review.
Morsli H, Choo D, Ryan A, Johnson R, Wu DK. Development of the mouse inner ear and origin of its sensory organs. J Neurosci. 1998 May 1;18(9):3327-35. J Neuroscience Link
Articles
Villa-Cuesta E, Modolell J. Mutual repression between msh and Iro-C is an essential component of the boundary between body wall and wing in Drosophila. Development. 2005 Aug 10
Goto M, Piper Hanley K, Marcos J, Wood PJ, Wright S, Postle AD, Cameron IT, Mason JI, Wilson DI, Hanley NA. In humans, early cortisol biosynthesis provides a mechanism to safeguard female sexual development. J Clin Invest. 2006 Apr;116(4):953-60.
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.
"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." (text edited from abstract) (More? OMIM ATONAL)
Rodriguez-Vazquez JF. Development of the stapes and associated structures in human embryos. J Anat. 2005 Aug;207(2):165-73.
"The stapedial anlage is a unique formation with two distinct parts: the superior part that will comprise the base and the inferior part that will be crossed by the stapedial artery during embryonic development and will constitute the limbs and the head of the stapes. According to the results, the otic capsule is not involved in formation of the base of the stapes."
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."
Molecular Normal Development
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.
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.
List of Ear Development Reviews (1998)
Reviews Abnormal Development (1998)
Webster WS. [See Related Articles] Teratogen update: congenital rubella. Teratology. 1998 Jul;58(1):13-23. Review.
Yates JA, et al. [See Related Articles] Isolated congenital internal auditory canal atresia with normal facial nerve function. Int J Pediatr Otorhinolaryngol. 1997 Jul 18;41(1):1-8. Review.
Lambert PR, et al. [See Related Articles] Congenital malformations of the external auditory canal. Otolaryngol Clin North Am. 1996 Oct;29(5):741-60. Review.
Lin AE, et al. [See Related Articles] Further delineation of the branchio-oculo-facial syndrome. Am J Med Genet. 1995 Mar 13;56(1):42-59. Review.
Strasnick B, et al [See Related Articles] Teratogenic hearing loss. J Am Acad Audiol. 1995 Jan;6(1):28-38. Review.
Kossowska E, et al. [See Related Articles] Prenatal and neonatal prophylaxis in otorhinolaryngology. Int J Pediatr Otorhinolaryngol. 1980 Jun;2(2):85-98. Review.
Gottlieb G. [See Related Articles] Conceptions of prenatal development: behavioral embryology. Psychol Rev. 1976 May;83(3):215-34. Review.
Holme RH, Steel KP Genes involved in deafness. Curr Opin Genet Dev 1999 Jun;9(3):309-314
"Remarkable progress has been made over the past few years in the field of hereditary deafness. To date, mutations in at least 35 genes are known to cause hearing loss. We are now beginning to understand the function of many of these genes, which affect diverse aspects of ear development and function.
Note: books are listed for educational and information purposes only and does not suggest a commercial product endorsement.
Molecular and Cellular Approaches to Neural Development
The Embryonic Human Brain: An Atlas Of Developmental Stages, 3rd Edition
Search PubMed
Search Mar2007 "hearing development" 7,453 reference articles of which 900 were reviews.
Search PubMed Now: term= hearing development | otic placode | inner ear development | middle ear development | outer ear development | abnormal hearing development
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altricial animal – born in a helpless state, incomplete development of sensory systems at birth (rats, mice).
ampulla –
aneurism - (Greek, aneurysma = a widening, aneurysm)
aquaeductus vestibuli
auditory neuropathy - (AN) abnormality of transmission of sound information to the brain.
Auditory tube – (eustachian tube) between the middle ear and oral cavity, has a bony (tympanic 1/3) and cartilaginous (pharyngeal 2/3) portion. The main role is equalization of pressure and fluid drainage in the middle ear.
auricular hillock - see hillock
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)
Cerumen - (ear wax) produced by glands in the skin of the outer portion of the ear canal.
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.
Endoderm –
endolymphatic fluid
endolymphatic sac - has secretory and absorptive functions and communicates with the subarachnoid space, within the connective tissue layers surrounding the brain.??
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}
Eustachian tube - (auditory tube) A cavity linking the pharynx to the middle ear, which develops from the first pharyngeal pouch. Named after Bartolomeo Eustachi (1500 - 1574) an Italian anatomist.
external auditory meatus - (ear canal) develops from the first pharyngeal cleft.
Ear wax – see cerumen.
Epithelia –
espins – calcium-resistant actin-bundling proteins enriched in hair cell stereocilia and sensory cell microvilli and spiral ganglion neurons (SGNs)
eustachian tube – (auditory tube) between the middle ear and oral cavity, equalization of pressure in the middle ear.
external auditory canal –
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 -
Incus - (anvil) auditory ossicle
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 -
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.
Malleus – (hammer) auditory ossicle
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
meatal plug – temporary blockage of the external auditory meatus which forms at the end of the embryonic period and remains present until the seventh month.
meatus – anatomical opening, cavity or space (external acoustic meatus,
internal auditory meatus)
Meckel’s cartilage – first pharyngeal ach cartilage, located within the mandibular prominence. This cartilage first appears at stage 16, stage 20 the beginning of membranous ossification. Named after Johann Friedrich Meckel, (1781 - 1833) a German anatomist. (http://www.whonamedit.com/doctor.cfm/1840.html)
membranous labyrinth -
Mesenchyme -
Mesoderm -
Microtia -
Modiolus –
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.
Ossicle – (small bone) the individual bone of the three middle ear bones (auditory ossicles), which reduce vibrational amplitude but increase force to drive fluid-filled 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.
paratubal musculature – muscles lying beside the auditory (Eustachian) tube. The tensor veli, palatini (TVP) and tensor tympani muscles.
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
Preyer reflex – ear flick in mouse in response to sound.
presbyacusis
Prestin – a motor protein structurally similar to the anion transporter family expressed in cochlear outer hair cells.
Preauricular Tag - skin tags located in front of the external ear opening, are common in neonates and in most cases are normal, though in some cases are indicative of other associated abnormalities.
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.
Reichert’s cartilage – pharyngeal ach 2 cartilage, named after Karl Bogislaus Reichert (1811 - 1883) a German anatomist.
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.
stapedius muscle - (innervated by CN VII tympanic branch) one of the two muscles in the middle ear, contraction of this muscle pulls the stapes and dampens auditory ossicle movement.
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).
stratified squamous epithelia – classification of epithelium which transiently forms a plug in external ear canal to the outer eardrum.
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 –
tensor tympani - (innervated by CN V mandibular nerve) one of the two muscles in the middle ear, contraction of this muscle pulls the malleus and tenses the tympanic membrane, dampening auditory ossicle movement. The muscle arises from auditory tube (cartilaginous portion) and is inserted into the malleus (manubrium near the root).
teratogens –
trilaminar embryo -
tonotopy – term describing the mapping along the tectorial membrane within the cochlea of the different sound frequencies.
tympanic cavity -
tympanic membrane -
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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Dev Biol (Gilbert)
These notes introduce the development of hearing and balance and has links to further specific notes on the development of the auditory and vestibular system.
Due to its complex development, hearing is the most prone of all our senses to abnormal development and to be impacted upon by both genetic and environmental (materal) effects (More? Hearing Abnormalities).
In Australia within NSW, there is now an early postnatal analysis of neonatal hearing as part of a State Wide Infant Screening Hearing Program using AABR (More? Neonatal Hearing Screening).
If you have not studied hearing development before, there is a link to 2008 ANAT2341 Lecture 17 Hearing and an earlier set of Science Lecture (2004) slides on Hearing Development, an overview of developmental timing and a text overview.
This first page introduces a broad overview of this sense, links on this page will take you to more specific information.
Please email Dr Mark Hill if you wish to make a comment about this current project.
