Sensory - Hearing and Balance Development

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Hearing cartoon.jpg

Introduction

Newborn hearing test

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.


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.


In Australia, there is now an early postnatal screening of neonatal hearing as part of a NSW State Wide Infant Screening Hearing (SWISH) Program using Automated Auditory Brainstem Response (AABR).


Use the hearing links below to see more detailed information about development of the three hearing divisions and abnormalities.


Hearing Links: Introduction | Science Lecture | Medicine Lecture | Inner Ear | Middle Ear | Outer Ear | Balance | Hearing - Neural Pathway | Stage 22 | Abnormalities | Neonatal Diagnosis - Hearing | Hearing test | Sensory Introduction | Placodes | Student project | Category:Hearing
Historic Embryology 
Historic Embryology: 1902 Development of Hearing | 1906 Membranous Labyrinth | 1913 Tectorial Membrane | 1918 Human Embryo Otic Capsule | 1918 Cochlea | 1918 Grays Anatomy | 1922 Human Auricle | 1922 Otic Primordia | 1931 Internal Ear Scalae | 1933 Endolymphatic Sac | 1934 Otic Vesicle | 1934 Membranous Labyrinth | 1963 Human Otocyst | Historic Disclaimer


Senses Links: Introduction | Placodes | Hearing and Balance | Vision | Smell | Taste | Touch | Stage 22 | Category:Senses

Some Recent Findings

  • Role of p63 and the Notch pathway in cochlea development and sensorineural deafness[1] "The ectodermal dysplasias are a group of inherited autosomal dominant syndromes associated with heterozygous mutations in the Tumor Protein p63 (TRP63) gene. Here we show that, in addition to their epidermal pathology, a proportion of these patients have distinct levels of deafness. ...these data demonstrate that TAp63, acting via the Notch pathway, is crucial for the development of the organ of Corti, providing a molecular explanation for the sensorineural deafness in ectodermal dysplasia patients with TRP63 mutations." Developmental Signals - Notch
  • Postnatal development primary auditory cortex[2] "The organization of the primary auditory cortex (A1) in particular is governed by acoustic experience during the critical period, an epoch near the beginning of postnatal development throughout which cortical synapses and networks are especially plastic. This neonatal sensitivity to the pattern of sensory inputs is believed to be essential for constructing stable and adequately adapted representations of the auditory world and for the acquisition of language skills by children."
  • Review - The etiology of otosclerosis[3] "Otosclerosis is a common form of hearing loss characterized by abnormal bone remodeling in the otic capsule. It is a complex genetic disease, caused by a combination of genetic and environmental factors. During the past decade, several attempts have been made to identify factors for otosclerosis."
More recent papers  
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  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
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References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

Links: References | Discussion Page | Pubmed Most Recent | Journal Searches


Search term: Hearing Development

Hua Ou, Ann Perreau, Richard Tyler Development of a Shortened Version of the Spatial Hearing Questionnaire (SHQ-S) for Screening Spatial-Hearing Ability. Am J Audiol: 2017;1-8 PubMed 28738135

Beth Brooks, Kristin Knight Ototoxicity monitoring in children treated with platinum chemotherapy. Int J Audiol: 2017;1-7 PubMed 28737048

Sianne Green, Munyane Mophosho, Katijah Khoza-Shangase Commuting and communication: An investigation of taxi drivers' experiences, attitudes and beliefs about passengers with communication disorders. Afr J Disabil: 2015, 4(1);91 PubMed 28730016

Wisdom K Mprah Sexual and reproductive health needs assessment with deaf people in Ghana: Methodological challenges and ethical concerns. Afr J Disabil: 2013, 2(1);55 PubMed 28729992

Wisdom K Mprah Knowledge and use of contraceptive methods amongst deaf people in Ghana. Afr J Disabil: 2013, 2(1);43 PubMed 28729988

Textbooks

  • Larsen's Human Embryology (4th ed.) Schoenwolf, Larsen, Bleyl, Brauer and Francis-West Chapter 17 Development of the Ears and Eyes
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 19: p491-511
  • Essentials of Human Embryology Larsen Chapter 12: p252-272
  • Before We Are Born (5th ed.) Moore and Persaud Chapter 20: p460-479
  • Journal of Cell Biology The Cell Biology of the Senses - The cell biology of hearing July 12, 2010 .

Embryonic Development

Comparison of size at stage 14 to 23

Based on data from the Carnegie embryo collection.[4][5]

Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Week 3

  • Stage 9 - otic placode (disc or otic zone) appears opposite the rhombencefhalic fold.[6][7]

Week 4

  • Stage 10 - 10 somites first indication of placode invagination[8] 12 somites cells migrate from the otic disc.[9]
  • Stage 11 - 16 somites otic pit is formed and lies dorsal to the second pharyngeal groove (cleft).[9]
  • Stage 12 - otic vesicle (otocyst) is forming and connects by a narrow pore with the surface[10] Otocyst ventral wall contributes to the vestibulocochlear crest.
  • Stage 13 - otic vesicle closes from surface and endolymphatic appendage apparent. A capillary network forms around the otic vesicle with esoderm becomes condensed as the otic capsule.[11] Vestibulocochlear ganglion (vestibular part) and vestibular nerve fires present.

Week 5

  • Stage 14 - otic vesicle ventral portion elongates to form the cochlear duct and endolymphatic appendage becomes tapered.[11]
  • Stage 15 - otic capsule formed by condensed mesenchyme. Ganglion vestibular nerve fibres extend to the otocyst epithelium. External ear auricular hillocks appear.

Week 6

  • Stage 16 - otic vesicle wall thickens prior to appearance of the semicircular ducts.[12] A utriculosaccular diverticulum and spiral ganglion appears. Auricular hillocks present (tragus, crus helicis, helix, and antitragus).
  • Stage 17 - otic capsule now dense mesenchyme. Otic vesicle vestibular part wall thins prior to semicircular duct appearing. Geniculate ganglion forms. Auditory ossicles, tubotympanic recess and chorda tympani appear. First pharyngeal groove (cleft or hyomandibular groove) begins to form the concha and the external acoustic meatus. Six auricular hillocks present (1 tragus, 2 and 3 crus helicis, 4 and 5 helix, and 6 antitragus).

Week 7

  • Stage 18 - otic capsule precartilaginous. Semicircular ducts form in the order anterior, posterior, and lateral from thickened epithelial areas and adjacent epithelial layers fuse. Cochlear duct is now L-shaped. First pharyngeal arch bar begins to chondrify (Meckel’s cartilage), second arch may chondrify (Reichert’s cartilage), stapes and stapedius commence. Auricular hillocks merge to form auricle primordia.
  • Stage 19 - otic capsule now cartilaginous. Cochlea tip becomes curled. Malleus and incus present.

Week 8

  • Stage 20 - otic capsule connected with the basal plate and with the future exoccipitals. Tip of the cochlea is elongated and curled. Tensor tympani and stapedius present.
  • Stage 21 - tip of the cochlea is recurved.
  • Stage 22 - cochlea continues spiral growth.
  • Stage 23 - cochlea shows nearly 21/2 turns. otic capsule cartilage separated from the semicircular ducts by a pre cartilaginous zone. Labyrinth has practically completed its gross development and ductus reuniens is well defined.[13]

Fetal

  • 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.
  • 2nd Trimester - (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.

Embryonic Origin Overview

Adult hearing embryonic origins

External Ear

  • Auricle - Pharyngeal Arches 1 and 2 (ectoderm, mesoderm)
  • External Auditory Meatus - Pharyngeal Arch 1 groove or cleft (ectoderm)
  • Tympanic Membrane - Pharyngeal Arch 1 membrane (ectoderm, mesoderm, endoderm)

Middle Ear

  • Middle Ear Ossicles
    • Malleus and incus - Pharyngeal Arch 1 cartilage Neural crest (ectoderm)
    • Stapes - Pharyngeal Arch 2 cartilage Neural crest (ectoderm)
  • Middle Ear Muscles
    • Tensor tympani - Pharyngeal Arch 1 (mesoderm)
    • Stapedius - Pharyngeal Arch 2 (mesoderm)
  • Middle ear cavity - Pharyngeal Arch 1 pouch (endoderm)

Inner Ear

  • Inner Ear Labyrinth
    • Cochlea - Otic vesicle - Otic placode (ectoderm)
    • Semicircular canals - Otic vesicle - Otic placode (ectoderm)
    • Saccule and utricle - Otic vesicle - Otic placode (ectoderm)
  • Cranial Nerve VIII
    • Auditory component - Otic vesicle and neural crest (ectoderm)
    • Vestibular component - Otic vesicle and neural crest (ectoderm)

Inner Ear

Stage 13 otocyst
Stage 22 ear
  • 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.

Links: Inner Ear

Middle Ear

  • 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.

Links: Middle Ear

Outer Ear

External ear stages 14-23 and adult (not to scale)
  • 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.

Links: Outer Ear

Postnatal Changes

Eustacian tube angle changes

There are a number of postnatal changes associated with growth of the head that affect the newborn to adult auditory tube and its functions. The auditory tube (Eustachian, otopharyngeal or pharyngotympanic) space connects the middle ear cavity to nasopharynx portion of pharynx.

Auditory Tube Functions

  • Ventilation - pressure equalization in the middle ear
  • Clearance - allow fluid drainage from the middle ear, tube is normally closed and opened by muscles

Auditory Tube Postnatal

  • Birth - (neonatal to early childhood) the tube is initially short (17-18 mm), narrower and runs almost horizontal. The tube is opened by a single muscle, tensor palati muscle.
  • Adult - the tube is longer (twice as long), wider and runs at approximately 45 degrees to the horizontal. Tube is opened by two separate muscles, tensor palati and levator palati.

Abnormalities

Microtia
Preauricular sinus

There are many different abnormalities of hearing development that can result in hearing loss and can broadly be divided into either conductive or sensorineural loss. These abnormalities can have genetic, environmental or unknown origins. In addition, abnormalities of the external ear (position and structure) is used as a clinical diagnostic tool for developmental abnormalities in other systems.

  • Inner ear - common cavity, severe cochlear hypoplasia
  • Middle ear - rare and can be part of first arch syndrome, Malleus, Incus and Stapes Fixation
    • Cholesteatoma- Epithelium trapped within skull base in development, erosion of bones: temporal bone, middle ear, mastoid
  • Outer ear - Several genetic effects and syndromes, Environmental Effects
    • Microtia - abnormally small external ear
    • Preauricular sinus - occurs in 0.25% births, bilateral (hereditary) 25-50%, unilateral (mainly the left), duct runs inward can extend into the parotid gland, Postnatally sites for infection

Links: Hearing Abnormalities

Congenital Deafness

Sensorineural - cochlear or central auditory pathway Conductive - disease of outer and middle ear

Sensorineural

  • 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
    • cytomegalovirus [14]
    • streptomycin
    • antibiotic
    • thalidomide

Conductive

  • disease of outer and middle ear
  • can be produced by otitis media with effusion, that is widespread in young children.
  • temporary blockage of outer or middle ear

Fetal Alcohol Syndrome

Fetal Alcohol Syndrome Face
  • Postion- Lower or uneven height, "railroad track” appearance, curve at top part of outer ear is under-developed, folded over parallel to curve beneath


Newborn Hearing Screening

Newborn hearing test

In Australia, there is now an early postnatal screening of neonatal hearing as part of a NSW State Wide Infant Screening Hearing (SWISH) Program using Automated Auditory Brainstem Response (AABR).

  • Very low birthweight infants and universal newborn hearing screening in a developing country[15]

Links: NSW Statewide Infant Screening - Hearing (SWISH) Program

Bionic Ear

The "Cochlear Implant" was pioneered in development by Professor Graeme Clark (1960s, Australia).[16] It consists of an array of electrodes implanted within cochlea, that directly electrically stimulate the auditory nerve fibres.

  • Young children with cochlear implants compared with children with normal hearing.[17]

References

  1. Isabelle Schrauwen, Guy Van Camp The etiology of otosclerosis: a combination of genes and environment. Laryngoscope: 2010, 120(6);1195-202 PubMed 20513039
  2. Anja L Dorrn, Kexin Yuan, Alison J Barker, Christoph E Schreiner, Robert C Froemke Developmental sensory experience balances cortical excitation and inhibition. Nature: 2010, 465(7300);932-6 PubMed 20559387
  3. Isabelle Schrauwen, Guy Van Camp The etiology of otosclerosis: a combination of genes and environment. Laryngoscope: 2010, 120(6);1195-202 PubMed 20513039
  4. O'Rahilly R. The early development of the otic vesicle in staged human embryos. (1963) J Embryol Exp Morphol., 11: 741-55 PMID 14081992
  5. R O'Rahilly The timing and sequence of events in the development of the human eye and ear during the embryonic period proper. Anat. Embryol.: 1983, 168(1);87-99 PubMed 6650859
  6. Bartelmez GW. The origin of the otic and optic primordia in man. (1922) J. Comp. Neural., 34: 201-232.
  7. Ingalls NW. A human embryo at the beginning of segmentation, with special reference to the vascular system. (1920) Contrib. Embryol., Carnegie Inst. Wash. Publ. 274, 11: 61-90.
  8. Corner GW. A well-preserved human embryo of 10 somites. (1929) Carnegie Instn. Wash. Publ. 394, Contrib. Embryol., 20: 81-102.
  9. 9.0 9.1 Bartelmez GW. and Evans HM. Development of the human embryo during the period of somite formation, including embryos with 2 to 16 pairs of somites. (1926) Contrib. Embryol., Carnegie Inst. Wash. Publ. 362, 17: 1-67.
  10. Streeter GL. Developmental horizons in human embryos. Description of age group XI, 13 to 20 somites, and age group XII, 21 to 29 somites. (1942) Contrib. Embryol., Carnegie Inst. Wash. Publ. 541, 30: 211-245.
  11. 11.0 11.1 Streeter GL. Developmental horizons in human embryos. Description of age group XIII, embryos about 4 or 5 millimeters long, and age group XIV, period of indentation of the lens vesicle. (1945) Carnegie Instn. Wash. Publ. 557, Contrib. Embryol., Carnegie Inst. Wash., 31: 27-63.
  12. Streeter GL. Developmental horizons in human embryos. Description of age groups xv, xvi, xvii, and xviii, being the third issue of a survey of the Carnegie collection. (1948) Contrib. Embryol., Carnegie Inst. Wash. 575, Contrib. to Embryol. 32: 133-203.
  13. Streeter GL. On the development of the membranous labyrinth and the acoustic and facial nerves in the human embryo. (1906) Amer. J Anat. 6:139-165.
  14. Yoav Yinon, Dan Farine, Mark H Yudin, Robert Gagnon, Lynda Hudon, Melanie Basso, Hayley Bos, Marie-Franc Delisle, Savas Menticoglou, William Mundle, Annie Ouellet, Tracy Pressey, Anne Roggensack, Marc Boucher, Eliana Castillo, Andrée Gruslin, Deborah M Money, Kellie Murphy, Gina Ogilvie, Caroline Paquet, Nancy Van Eyk, Julie van Schalkwyk, Fetal Medicine Committee, Society of Obstetricians and Gynaecologists of Canada Cytomegalovirus infection in pregnancy. J Obstet Gynaecol Can: 2010, 32(4);348-54 PubMed 20500943
  15. Bolajoko O Olusanya Perinatal profile of very low birthweight infants under a universal newborn hearing screening programme in a developing country: a case-control study. Dev Neurorehabil: 2010, 13(3);156-63 PubMed 20450464
  16. Graeme M Clark Personal reflections on the multichannel cochlear implant and a view of the future. J Rehabil Res Dev: 2008, 45(5);651-93 PubMed 18816421 JRRD
  17. Bianka Schramm, Andrea Bohnert, Annerose Keilmann Auditory, speech and language development in young children with cochlear implants compared with children with normal hearing. Int. J. Pediatr. Otorhinolaryngol.: 2010, 74(7);812-9 PubMed 20452685

Online Textbooks

Reviews

Martin Schwander, Bechara Kachar, Ulrich Müller Review series: The cell biology of hearing. J. Cell Biol.: 2010, 190(1);9-20 PubMed 20624897

| JCB

The International Journal of Developmental Biology Vol. 51 Nos. 6/7 (2007) Ear Development

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Terms

Hearing Terms  
Hearing and Balance Development
  • 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? Animal Development)
  • 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)
  • aneurism - (Greek, aneurysma = a widening, aneurysm) A term used to describe an abnormal widening of a vessel or anatomical tubal structure.
  • aquaeductus vestibuli - see vestibular aqueduct (More? Inner Ear)
  • 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. (More? Middle Ear)
  • auricular hillock - see hillock (More? Middle Ear)
  • 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. (More? Inner Ear)
  • 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) (More? Inner Ear)
  • cerumen - (ear wax) produced by glands in the skin of the outer portion of the ear canal. (More? Outer Ear)
  • 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. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • cochlear sac - embryonic structure, which will form the coiled cochlear duct and contribute to the saccule. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • cochlin - major constituent of the inner ear extracellular matrix. (More? Inner Ear)
  • collagen type II - major constituent of the inner ear extracellular matrix. (More? Inner Ear)
  • 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
  • cupular deposits - basophilic material on the cupulae of the semicircular ducts, an postnatal ageing phenomenon seen in some vestibular labyrinth. (More? Inner Ear)
  • clinical weeks - taken from last menstrual period (LMP) and therefore approximately two weeks before fertilization occurs.
  • Deiters' cells - (outer phalangeal 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 - (More? Inner Ear)
  • endochondral ossification - the process of bone formation from a pre-existing cartilage template. (More? Middle Ear)
  • endoderm - One of the initial 3 germ cell layers (ectoderm, mesoderm and endoderm) formed by the process of gastrulation. The endoderm forms as a cuboidal epithelium and contributes not only to the trilaminar embryo, but also lines the yolk sac. It will form the entire epithelial lining of the gastrointestinal tract (GIT), contribute to the accessory organs of GIT and also forms the epithelial lining of the respiratory tract.
  • endolymphatic fluid - (endolymph, Scarpa's fluid) fluid that fills all the membranous labyrinth of the inner ear, except for the cochlea scala tympani and scala vestibuli which are filled with perilymph.
  • 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. (More? Inner Ear)
  • 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. (More? Embryonic Development)
  • Emx2 - homeobox gene affecting middle ear and inner ear development.
  • 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. (More? Middle Ear)
  • external auditory meatus - (ear canal) develops from the first pharyngeal cleft. (More? Outer Ear)
  • ear wax - see cerumen. (More? Outer Ear)
  • 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. (More? Middle Ear)
  • external auditory meatus - (EAM, ear canal) cavity connecting the external ear to the tympanic membrane. The adult human ear canal is about 2.5 cm long and 0.7 cm in diameter. (More? Outer Ear)
  • fenestra ovalis - (oval window) separates the tympanic cavity from the vestibule of the osseous labyrinth. (More? Inner Ear)
  • fenestra rotunda - (round window) separates the tympanic cavity from the scala tympani of the cochlea. (More? Inner Ear)
  • 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.
  • fibroblast growth factor 8 - (Fgf-8) a growth factor released by inner hair cells which regulates pillar cell number, position and rate of development.
  • 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
  • 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. (More? Inner Ear)
  • Hes - (hairy and enhancer of split) family of factors, which has been shown to be a general negative regulator of neurogenesis (Zheng, 2000).
  • hillock - a small hill, used to describe the six surface elevations on pharyngeal arch one and two. (More? Outer Ear)
  • Incus - (anvil) auditory ossicle (More? Middle Ear)
  • inner phalangeal cells - in the cochlea a single row of cells, that along with and three rows of outer phalangeal cells (Deiter's cells), are the hair cell supporting cells. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • inner sulcus - area of the cochlear duct. (More? Inner Ear)
  • 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? Inner Ear)
  • kinocilium - inner ear hair cell specialised type of cilium on the cell apex.
  • Kolliker's organ - (Kollicker'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)?? (More? Inner Ear)
  • lateral semicircular duct
  • limbus -
  • LMP - acronym for last menstrual period, used to clinically measure gestation.
  • malleus - (hammer) auditory ossicle (More? Middle Ear)
  • mastoid process - of temporal bone (More? Middle Ear)
  • Math1 - homolog of the Drosophila proneural gene atonal, necessary and sufficient for the production of hair cells in the mouse inner ear. 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)
  • mechano-electrical transduction - (MET) occurs within the cochlear hair cells hair bundle. A mechanical stimulus of the hair bundle causes the tip-links to be tensioned, opening ion channels, resulting in the generation of the cell receptor potential. (More? Inner Ear)
  • 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) (More? Middle Ear)
  • membranous labyrinth - (More? Inner Ear)
  • 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. (More? Inner Ear)
  • otoacoustic emissions testing - (OET) hearing test measures sounds generated by the outer hair cells of the cochlea in response to clicks or tone bursts emitted and recorded by a tiny microphone placed in the infant’s external ear canal. (More? Hearing test)
  • olivocochlear - brainstem cholinergic and GABAergic efferent system that innervates sensory cells and sensory neurons of the inner ear.
  • organ of Corti - (More? Inner Ear)
  • organ of Corti protein II - (OCP-II) cytosolic protein or transcription factor? (More? Inner Ear)
  • otolithic membrane - extracellular matrix that cover the sensory epithelia of the inner ear. (More? 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. (More? Middle Ear)
  • ossify - (More? Middle Ear)
  • otic capsule -
  • otic cup -
  • otic placode - Embryonic ectodermal epithelium giving rise to inner ear structures. (More? Inner Ear | Placodes)
  • otic vesicle - (More? Inner Ear)
  • otoconin - inner ear biominerals required for vestibular apparatus function. (More? Inner Ear)
  • otogelin - (Otog) an inner ear specific glycoprotein expressed in cochlea cells at different developmental times. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • paratubal musculature - muscles lying beside the auditory (Eustachian) tube. The tensor veli, palatini (TVP) and tensor tympani muscles. (More? Middle Ear)
  • 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.
  • pharyngeal arch - (More? Outer Ear) 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. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • 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.
  • 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. (More? Inner Ear)
  • semicircular canals - series of fluid-filled loops of the inner ear required for balance and sensing acceleration. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • spiral ganglion neurons - (SGN) innervate the inner (Type I) and outer (Type II) hair cells of the cochlea. (More? Inner Ear)
  • 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. (More? Middle Ear)
  • stapes - (stirrup) a middle ear auditory ossicle (bone) (More? Middle Ear)
  • stapes footplate - (More? Middle Ear)
  • 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. (More? Inner Ear)
  • sulcus -
  • synostotically - anatomically normally separate skeletal bones fused together. (More? Middle Ear)
  • tectorial membrane - within the cochlea an extracellular matrix produced by interdental cells, that covers the sensory epithelial hair cells of the organ of corti. (More? Inner Ear)
  • 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.
  • temporal bone - (More? Middle Ear)
  • 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 -
  • tonotopy - term describing the mapping along the tectorial membrane within the cochlea of the different sound frequencies. (More? Inner Ear)
  • tympanic membrane - (ear drum)
  • 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. (More? Inner Ear)
  • 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. (More? Inner Ear)
  • 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). (More? Inner Ear)
  • Wnt7a - signaling through the Wnt pathway regulates the development of hair cell unidirectional stereociliary bundle orientation. (More? Inner Ear)
Other Terms Lists  
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Cite this page: Hill, M.A. 2017 Embryology Sensory - Hearing and Balance Development. Retrieved July 26, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/Sensory_-_Hearing_and_Balance_Development

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© Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G