Lecture - Sensory Development

Introduction

Human embryo sensory placodes (Week 5, stage 14)

This lecture will introduce development of the special sensory structures associated with hearing, vision, smell and taste. Due to time limitations the lecture will focus on hearing development and if time is available vision and other senses will be introduced in general.

Hearing Development	Vision Development	Smell Development	Taste Development

Adult hearing embryonic origins

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.

Objectives

• Understanding of sensory placode development
• Understanding of inner, middle and external ear origins
• Understanding of timecourse of auditory development
• Understanding of abnormalities of auditory development
• Brief understanding of other (vision) sensory development

Also review your Head development lecture.

Lecture Resources

Movies and Virtual Slides
‎‎Hearing Page | Play	‎‎Head Stage 15-22 Page | Play	Stage 22 - Eye and Nose  ‎‎Mobile | Desktop | Original Stage 22 | Embryo Slides	Stage 22 - Eye  ‎‎Mobile | Desktop | Original Stage 22 | Embryo Slides	Stage 22 - Oral Cavity and Inner Ear  ‎‎Mobile | Desktop | Original Stage 22 | Embryo Slides

References
	2015 | 2015 PDF | 2014 | 2014 PDF
Hill, M.A. (2020). UNSW Embryology (20th ed.) Retrieved December 11, 2023, from https://embryology.med.unsw.edu.au	Senses Links: Introduction | placode | Hearing and Balance hearing | balance | vision | smell | taste | touch | Stage 22 | Category:Sensory Hearing Links: Introduction | inner ear | middle ear | outer ear | balance | placode | hearing neural | Science Lecture | Lecture Movie | Medicine Lecture | Stage 22 | hearing abnormalities | hearing test | sensory | Student project   Categories: Hearing | Outer Ear | Middle Ear | Inner Ear | Balance Historic Embryology - Hearing  Historic Embryology: 1880 Platypus cochlea | 1892 Vertebrate Ear | 1902 Development of Hearing | 1906 Membranous Labyrinth | 1910 Auditory Nerve | 1913 Tectorial Membrane | 1918 Human Embryo Otic Capsule | 1918 Cochlea | 1918 Grays Anatomy | 1922 Human Auricle | 1922 Otic Primordia | 1931 Internal Ear Scalae | 1932 Otic Capsule 1 | 1933 Otic Capsule 2 | 1936 Otic Capsule 3 | 1933 Endolymphatic Sac | 1934 Otic Vesicle | 1934 Membranous Labyrinth | 1934 External Ear | 1938 Stapes - 7 to 21 weeks | 1938 Stapes - Term to Adult | 1940 Stapes | 1942 Stapes - Embryo 6.7 to 50 mm | 1943 Stapes - Fetus 75 to 150 mm | 1946 Aquaductus cochleae and periotic (perilymphatic) duct | 1946 aquaeductus cochleae | 1948 Fissula ante fenestram | 1948 Stapes - Fetus 160 mm to term | 1959 Auditory Ossicles | 1963 Human Otocyst | Historic Disclaimer Vision Links: vision | lens | retina | placode | extraocular muscle | cornea | eyelid | lacrima gland | vision abnormalities | Student project 1 | Student project 2 | Category:Vision | sensory Historic Embryology - Vision  Historic Embryology: 1906 Eye Embryology | 1907 Development Atlas | 1912 Eye Development | 1912 Nasolacrimal Duct | 1917 Extraocular Muscle | 1918 Grays Anatomy | 1921 Eye Development | 1922 Optic Primordia | 1925 Eyeball and optic nerve | 1925 Iris | 1927 Oculomotor | 1928 Human Retina | 1928 Retina | 1928 Hyaloid Canal | Historic Disclaimer Taste Links: Introduction | Student project | Tongue Development | Category:Taste Historic Taste  Historic Embryology: 1888 human infant papilla foliata | 1889 man taste-organs | Paper - Further observations on the development of the taste-organs of man|1889 further man taste-organs]]
Moore, K.L., Persaud, T.V.N. & Torchia, M.G. (2015). The developing human: clinically oriented embryology (10th ed.). Philadelphia: Saunders.	The following chapter links only work with a UNSW connection. Development of Eyes and Ears
Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R., Francis-West, P.H. & Philippa H. (2015). Larsen's human embryology (5th ed.). New York; Edinburgh: Churchill Livingstone.	UNSW students have full access to this textbook edition through UNSW Library subscription (with student Zpass log-in). Development of the Ears Development of the Eyes

2016 Lecture Video Recording
This 2016 lecture video recording is similar in content to the current 2017 online lecture. <html5media height="600" width="800">File:2016Lecture-Hearing.mp4</html5media> Click to play new window - 2016 Lecture Video (51 MB)

Development Timing

Comparison of embryonic size (week 4 - 8)

• 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.

Embryonic Origin Overview

Adult Hearing - Embryonic Origins

Outer Ear	Middle Ear	Inner Ear
Auricle - pharyngeal arch 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 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 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)

Sensory Placodes

Week 4
Otic placodes (Stage 11 dorsal view)	Sensory placodes ((Stage 14 ventral view)

• week 4 a series of thickened surface ectodermal patches form in pairs in the head region.
  • Recent research suggests that all sensory placodes may arise from common panplacodal primordium origin around the neural plate, and then differentiate to eventually have different developmental fates. PMID 20801420

• sensory placodes will later contribute key components of each of our special senses (vision, hearing and smell).
• Other species have a number of additional placodes which form other sensory structures (fish, lateral line receptor).
• Note that their initial postion on the developing head is significantly different to their final position in the future sensory system.

Otic Placode

• stage 13/14 embryo (shown below) the otic placode has sunk from the surface ectoderm to form a hollow epithelial ball, the otocyst, which now lies beneath the surface surrounded by mesenchyme (mesoderm).
• The epithelia of this ball varies in thickness and has begun to distort, it will eventually form the inner ear membranous labyrinth.

Lens Placode

• lies on the surface, adjacent to the outpocketing of the nervous system (which will for the retina) and will form the lens.

Nasal Placode

• 2 large components (medial and lateral), will form the nasal olefactory epithelium.

• • Note the extension of the (neural tube) diencephalon forming the optic stalk underlying the optic placode.

Inner Ear

Described in detail later in lecture.

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 | Neuroscience - The Inner Ear

Middle Ear

• derived from first pharyngeal pouch and 1st and 2nd arch mesenchyme
• extends as tubotympanic recess - during week 5 recess contacts outer ear canal
• mesoderm between 2 canals forms tympanic membrane
• expands to form tympanic recess
• stalk of recess forms auditory tube(eustachian tube, pharyngotympanic tube)

Ossicles 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. remains connected to the oral cavity by the auditory tube. ossicles connected with tympanic cavity walls by ligaments (3 for the malleus, and 1 each for the incus and stapes). Adult Ossicles Malleus Incus Stapes

Pharyngeal arch cartilages

Tympanic Cavity tympanic cavity enlarges to incorporate coats with epithelia first arch mesoderm - tensor tympani muscle second arch mesoderm - stapedius muscle

Cavities formed from the First Cleft

Middle Ear Genes - gooscoid, RARs, Prx1, Otx2, Hoxa1, Hoxb1, endothelian related molecules

Links: Middle Ear | Neuroscience - The Middle Ear

Outer Ear

• External ear is derived from 6 surface hillocks, 3 on each of pharyngeal arch 1 and 2.
  • structure completed during embryonic period.
• External auditory meatus is derived from the 1st pharyngeal cleft.
  • transiently blocked during development.
• The newborn external ear structure and position is an easily accessible diagnostic tool for potential abnormalities or further clinical screening.

Pinna- Auricle

Develops from six aural hillocks 3 on first arch 3 on second arch originally on neck, moves cranially during mandible development

arch 1 and 2 hillocks

Pharyngeal Arch	Hillock	Auricle Component
Arch 1	1	tragus
	2	helix
	3	cymba concha
Arch 2	4	concha
	5	antihelix
	6	antitragus

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

External auditory meatus

• derived from first pharyngeal cleft
• ectodermal diverticulum
• week 5 - extends inwards to pharynx
• until week 18 has ectodermal plug - plug forms stratified squamous epithelia of canal and outer eardrum

Timeline

Embryonic Period - Ectodermal cells proliferate and fill the entire lumen forming a meatal plug 10 weeks - Meatal plug extends in a disc-like fashion. In the horizontal plane the meatus is boot-shaped with a narrow neck and the sole of the meatal plug spreading widely to form the future tympanic membrane medially. Proximal portion of the neck starts to be resorbed. 13 weeks - Disc-like plug innermost surface in contact with the primordial malleus, contributes to the formation of the tympanic membrane. 16.5 week - Meatus is fully patent throughout its length, lumen is still narrow and curved. 18 week - Meatus is already fully expanded to its complete form. (EAM data - Nishimura, 1992 PMID 1441991)

outer ear and external auditory meatus

Links: Outer Ear | Neuroscience - The External Ear

Inner

Otic placodes (Stage 11 dorsal view)

Otocyst

Carnegie Stage 12 otic placode

Carnegie Stage 13 otic vesicle

• 
• 
• 
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  beginning of cochlea and semicircular canals

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  Week 8 cochlea

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• 

• week 3 otic placode forms on surface ectoderm
• otic placode sinks into mesoderm
• forms otocyst (otic vesicle)
• branches form and generate endolymphatic duct and sac
• forms vestibular (dorsal) and cochlear (ventral) regions
• differentiation of otic vesicle to membranous labyrinth

Vestibular Sac

• generates 3 expansions - form semicircular ducts
• remainder forms utricle
• epithelia lining generates - hair cells, ampullary cristae, utricular macula
• Vestibular - Otoconia, otoconin- inner ear biominerals

Cochlear sac

generates coiled cochlear duct (humans 2 1/2 turns) remainder forms saccule epithelia lining generates hair cells structures of organ of corti (differentiates in second trimester) saccular macula stria vascularis functions to synthesise and secretes endolymph.

Inner ear hair cells

Bony Labyrinth

• formed from chrondified mesoderm
• Periotic Capsule
• mesenchyme within capsule degenerates to form space filled with perilymph

Vestibulocochlear Nerve

• forms beside otocyst
• from wall of otocyst and neural crest cells
• bipolar neurons
• vestibular neurons
  • outer end of internal acoustic meatus
  • innervate hair cells in membranous labyrinth
  • axons project to brain stem and synapse in vestibular nucleus
• cochlear neurons
  • cell bodies lie in modiolus
  • central pillar of cochlear
  • innervate hair cells of spiral organ
  • axons project to cochlear nucleus

Inner Ear Genes

• hindbrain segmentation occurs at same time placode arises
• otocyst adjacent to rhombomere 5
• may influence development
• Hoxa1, kreisler, Fgf3
• genes regulating neural crest cells (neural genes)
• Pax2 Ko affects cochlear and spiral ganglion, but not vestibular apparatus
• nerogenin 1 affects both ganglia

Semicircular canal

• Otx1- cochlear and vestibular normal

• Hmx3, Prx1, Prx2

Sensory Organs

• thyroid hormone receptor beta
• Zebrafish-mindbomb mutant has excess hair cells but not supporting cells, Notch-Delta signaling

• Gene Expression-inner ear

• Brn-3c and Hair cell development
• Supporting Cells- p27kip
• Thyroid Hormone
• Ganglion neurons require growth factors
• vestibular neurons- BDNF, NT3
  • survival not development

Postnatal Changes

Eustacian tube angle changes

Newborn to adult Eustachian (auditory, otopharyngeal or pharyngotympanic) tube.

• Connects middle ear cavity to nasopharynx portion of pharynx

Functions

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

At birth

• shorter (17-18 mm), narrower and runs almost horizontal Tube is opened by a single muscle, tensor palati muscle

Adult

• 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

Vision

Timeline

Weeks 3-4 - Eye Fields-Optic Vesicle Weeks 5-6 - Optic Cup, Lens Vesicle, Choroid Fissure, Hyaloid Artery Weeks 7-8 - Cornea, Anterior Chamber, Pupillary Membrane, Lens, Retina Weeks 9-15 - Iris, Ciliary Body Weeks 8-10 - Eyelids

Stage 13 (week 5)

B1L	B2L	B3L	B4L	B5L	B6L	B7L

Lens

Surface ectoderm -> lens placode (optic placode) -> lens pit -> lens vesicle -> lens fibres -> lens capsule and embryonic/fetal nucleus.

Retina

Neural plate ectoderm -> prosencephalon (forebrain) eye fields -> neural plate growth carries eye field region forward -> eye field invaginates forming optic grooves (sulci) -> diencephalon optic groove interacts with surface ectoderm (induces optic placode) -> optic stalk -> optic vesicle -> folds inward (optic cup) forming double layer -> inner neural retina, outer pigmented retina

Links: Embryo Images - Eye Development

Neural Crest

Eye connective tissue

Abnormalities

vestibular sac abnormality

• Inner - common cavity, severe cochlear hypoplasia
  • Large vestibular aqueduct syndrome (LVAS) can be one of the common causes of hearing loss
• Middle - 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 - Several genetic effects and syndromes, Environmental Effects

Outer Ear Abnormalities

Microtia

Preauricular sinus

• 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

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

Congenital Deafness

Sensorineural - cochlear or central auditory pathway

• 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
  • streptomycin
  • antibiotic
  • thalidomide

Conductive - disease of outer and middle ear

Eustacian tube angle

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

Bionic Ear

Cochlear Implant - Professor Graeme Clark (1960s, Australia) Array of electrodes implanted within cochlea, direct electrical stimulation to auditory nerve fibres

Conductive Hearing Loss

• Conductive Hearing Loss Produces a Reversible Binaural Hearing Impairment David R. Moore, Jemma E. Hine, Ze Dong Jiang, Hiroaki Matsuda, Carl H. Parsons, and Andrew J. King J. Neurosci. 1999;19 8704-8711 http://www.jneurosci.org/cgi/content/abstract/19/19/8704
  • tested ferrets by lon-term plugging of ear canal
  • Repeated testing during the 22 months after unplugging revealed a gradual return to normal levels of unmasking.
  • Results show that a unilateral conductive hearing loss, in either infancy or adulthood, impairs binaural hearing both during and after the hearing loss.
  • Show scant evidence for adaptation to the plug and demonstrate a recovery from the impairment that occurs over a period of several months after restoration of normal peripheral function.

References

Textbooks

• Before We Are Born (5th ed.) Moore and Persaud Chapter 20: p460-479
• Essentials of Human Embryology, Larson Chapter 12: p252-272

Online Textbooks

• 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

• Bookshelf hearing development

• Pubmed hearing development

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

• NIDCD - Balance Disorders
• Embryo Images Online
  • Eye Development - Eye Development Unit | Eye Fields-Optic Vesicle (Weeks 3-4) | Optic Cup, Lens Vesicle, Choroid Fissure, Hyaloid Artery (Weeks 5-6) | Cornea, Anterior Chamber, Pupillary Membrane, Lens, Retina (Weeks 7-8) | Iris, Cilliary Body (Weeks 9-15) | Eyelids (Weeks 8-10)
  • Ear Development - Ear Development Unit | Inner Ear | [http://www.med.unc.edu/embryo_images/unit-ear/ear_htms/ear012.htm Middle Ear | External Ear

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. ductus utriculosaccularis - inner ear structure, a canal from the utricle that joins the ductus endolymphaticus from the saccule posterior wall, and then passes along the aquaductus vestibuli and ends in a blind pouch (saccus endolymphaticus) in the petrous portion of the temporal bone, also in contact with the dura mater. (More? image | balance | 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. Glaserian fissure - (petrotympanic fissure, squamotympanic fissure) the fissure in the temporal bone that runs between the temporomandibular joint to the tympanic cavity. Named after Johann Glaser (1629–1675) a Swiss anatomist. helicotrema - term used to describe the cochlear apex. (More? inner ear) Hensen’s stripe - within the cochlea tectorial membrane a ridge that runs longitudinally along the lower surface immediately adjacent to the hair bundles of the inner hair cells. 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) kimura membrane - (Kimura’s membrane) within the cochlea tectorial membrane a thickening of the lower surface into which the hair bundles of the outer hair cells are imbedded. 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 - (external) (More? image) 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 - (spiral organ) cochlea component required for converting vibration into neural signals. (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, auditory ossicles) the individual bone of the three middle ear bones (malleus, incus, stapes), which reduce vibrational amplitude but increase force to drive fluid-filled inner ear. (More? middle ear) ossify - to form bone. (More? middle ear | bone) otic capsule - otitis media -  ICD-11 [1] middle ear infection, peak age prevalence is 6 to 18 months old with many children (75%) have at least one episode by school age. Forms include on-suppurative, suppurative, acute otitis media, chronic otitis media. (More? hearing abnormalities, hearing test) otic cup - the early embryonic transient structure formed by the invagination (folding inward) of the otic placode, to cup, then vesicle stage. This will eventually form inner ear structures. otic placode - Embryonic ectodermal epithelium giving rise to inner ear structures. (More? inner ear | Placodes) otic vesicle - the early embryonic transient structure formed by the invagination (folding inward) and fusion of the otic cup, separating this structure from the embryo surface. This will eventually form inner ear structures.(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. (More? {{hearing abnormalities) 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 - the fluid between the membraneous labyrinth of the ear and the bone which encloses it. perilymphatic space - the space between the outer wall of the membranous labyrinth and the wall of the bony labyrinth that contains the perilymph. periotic capsule - periotic duct PMID 7003276 petrous portion of temporal bone - pejvakin gene - in humans, two missense mutations in this gene cause non-syndromic recessive deafness (DFNB59) by affecting the function of auditory neurons. petrotympanic fissure - (Glaserian fissure, squamotympanic fissure) the fissure in the temporal bone that runs between the temporomandibular joint to the tympanic cavity. 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 - age-related hearing loss, is the cumulative effect of aging on hearing. 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 arch 2 cartilage, named after Karl Bogislaus Reichert (1811 - 1883) a German anatomist. (More? middle ear | pharyngeal arch) 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 - hindbrain rostrocaudal segmentation established by expression of Hox homeodomain transcription factors. Histologically rhombomeres are visible as undulating folds (scalloping) of the neural tube in the hindbrain region and have associated cranial nerves. saccular macula - (macula of saccule) thickened anterior part of the saccule containing the saccular filaments of the acoustic nerve. (More? balance) Saccule - (Latin, sacculus = a small pouch) sensory cells in the inner ear that translate head movements into neural signals for the brain to interpret. (More? balance) sacculocollic reflex - thought to have a role in maintaining the relative position of the head and the body against the vertical linear acceleration of gravity. 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 - {Moro reflex) 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) tympanic ring - an incomplete circle, in the concavity of which is a groove, the tympanic sulcus, for the attachment of the circumference of the tympanic membrane. In the newborn the ring is still open and expands laterally to form the tympanic part of temporal bone. utricle - vacuolization - vesicle - vestibular apparatus - vestibular evoked myogenic potential - (VEMP) a test for vestibular disorders (utricle and superior nerve) response elicited by loud clicks or tone bursts recorded from the tonically contracted sternocleidomastoid muscle. 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 CN 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   Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Endocrine | Gastrointestinal | Genital | Genetic | Head | Hearing | Heart | Immune | Integumentary | Neonatal | Neural | Oocyte | Palate | Placenta | Radiation | Renal | Respiratory | Spermatozoa | Statistics | Tooth | Ultrasound | Vision | Historic | Drugs | Glossary