Lecture - Sensory Development

From Embryology

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.



2017 Students - Please note this draft online lecture content is currently being updated for the current course. This notice removed when update completed.


Hearing cartoon.jpg Stage 22 image 153.jpg Stage 22 image 209.jpg Tongue - taste cartoon.jpg
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 sensory development


Also review your Head development lecture.

Lecture Resources

Movies and Virtual Slides  
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 ‎‎Head Stage 15-22
Page | Play
Stage 22 - Eye and Nose

Stage 22 image 008.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Eye

Stage 22 image 008-eye.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Oral Cavity and Inner Ear

Stage 22 image 011.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
References  
2015 PDF | 2014 | 2014 PDF
UNSW Embryology logo
Hill, M.A. (2017). UNSW Embryology (17th ed.) Retrieved September 23, 2017, from https://embryology.med.unsw.edu.au
Senses Links: Introduction | Placodes | Hearing and Balance | Vision | Smell | Taste | Touch | Stage 22 | Category:Senses
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
Vision Links: Introduction | Lens | Retina | Placodes | Extraocular Muscle | Cornea | Eyelid | Abnormalities | Student project 1 | Student project 2 | Category:Vision
Historic Vision Embryology  
1906 Eye Embryology | 1907 Development Atlas | 1912 Eye Development | 1912 Nasolacrimal Duct | 1918 Grays Anatomy | 1921 Eye Development | 1922 Optic Primordia | Historic Disclaimer
Taste Links: Introduction | Student project | Tongue Development | Category:Taste
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.
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 Timing

Comparison of size at stage 14 to 23
  • 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.jpg

Adult hearing embryonic origins

Outer Ear Middle Ear Inner 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 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

Stage11 sem20.jpg Stage14 sem2l.jpg
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.

Stage 13 image 052.jpg

Lens Placode

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

Stage 13 image 058.jpg

Nasal Placode

  • 2 components (medial and lateral) and will form the nose olefactory epithelium.

Stage 13 image 061.jpg

Inner Ear

Described in detail later in lecture.

Stage13 otocyst.jpg

Stage 13 otocyst Stage22 ear.jpg

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
Gray0916.jpg Gray0917.jpg Gray0918.jpg
Malleus
Incus
Stapes
Pharyngeal arch cartilages.jpg

Pharyngeal arch cartilages

Tympanic Cavity
  • tympanic cavity enlarges to incorporate
  • coats with epithelia
  • first arch mesoderm - tensor tympani muscle
  • second arch mesoderm - stapedius muscle
Keith1902 fig039.jpg Keith1902 fig040.jpg

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

  • 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 ear stages-14-23-adult.jpg

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

Pinna- Auricle

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

External ear anatomy.jpg

Streeter1922-plate01.jpg

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
  • Outer- 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)

Gray0908.jpg

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
  • 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.
Stage 22 image 218.jpg
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)

Stage 13 image 057.jpg Stage 13 image 058.jpg Stage 13 image 059.jpg Stage 13 image 060.jpg Stage 13 image 061.jpg Stage 13 image 062.jpg Stage 13 image 063.jpg
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

Eye and retina cartoon.jpg

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

Search

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.

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  
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Gastrointestinal | Genetic | Hearing | Heart | Immune | Integumentary | Neural | Oocyte | Palate | Placenta | Renal | Respiratory | Spermatozoa | Ultrasound | Vision | Historic | Glossary
Vision Terms  
  • annular tendon - (common tendinous ring, annulus of Zinn) fibrous tissue surrounding the optic nerve forming the origin for five of the six extra ocular muscles.
  • AXIN2 - a scaffold protein that is an antagonist and universal target of the Wnt/β-catenin pathway required for visual development. OMIM - AXIN2
  • canthus - (palpebral commissure) the corner of the eye where the upper and lower eyelids meet.
  • cranial nerve 2 - (CN II, optic nerve) the cranial nerve consisting of retinal ganglion cell axons and glia forming the connection with the brain (pathway: retina, optic disc, optic chiasma, optic tract, lateral geniculate nucleus, pretectal nuclei, and superior colliculus).
  • extraocular muscles - six muscles that control movement of the eye (superior, Inferior, lateral and medial rectus; superior and inferior oblique).
  • fovea - (fovea centralis; Latin, fovea = pit) retina region located in the center of the macula, required for sharp central vision.
  • ganglion cell layer - (retinal ganglion layer) the layer of the retina where retinal ganglion cell bodies lie.
  • macula - (Latin, macula = spot; lutea = yellow) region near the center of the retina containing two or more layers of ganglion cells.
  • nasolacrimal groove - (lacrimal groove) an embryonic surface feature between the maxillary and the lateral nasal process that will later fuse to form the lacrimal duct running between the eye and the nasal inferior meatus.
  • optic chiasm (optic chiasma) CN II region where some of the axons (partial) cross to the opposite side.
  • optic cup - the in-folded extension of the optic stalk from the diencephalon that forms the retina.
  • optic disc - (optic nerve head) region on the retina where the retinal ganglion cells exit to form CN II.
  • optic placode - (lens placode) surface ectoderm that folds inward to form the developing lens.
  • retina - The stratified sensory structure of the eye, formed from the neural ectoderm that extends from the forebrain (diencephalon) to form initially the folded optic cup. Vertebrates have ten identifiable layers formed from nerve fibers, neurons, membranes, photoreceptors and pigmented cells. Light must pass through nearly all these layers to the photoreceptors. (1. Inner limiting membrane - Müller cell footplates; 2. Nerve fiber layer; 3. Ganglion cell layer - layer of retinal ganglion cells their axons form the nerve fiber layer and eventually the optic nerve; 4. Inner plexiform layer - another layer of neuronal processes; 5. Inner nuclear layer; 6. Outer plexiform layer; 7. Outer nuclear layer; 8. External limiting membrane - layer separating inner segment portions of photoreceptors from their cell nuclei; 9. Photoreceptor layer - rods and cones that convert light into signals; 10. Retinal pigment epithelium).
  • retinal pigment epithelium - (RPE, pigmented layer) An epethial pigmented cell layer lying outside the sensory retina, formed from the outer layer of the folded optic cup. The RPE is firmly attached to the underlying choroid and overlying retinal visual cells, for which it has a nutritional role.
  • retinal waves - A form of coordinated spontaneous activity that occurs in the developing retina. These waves of electrical activity (action potentials) along with EphA/ephrin-A signaling are thought to have a role in establishing the initial retinotopic map by correlating/coordinating the activity of neighbouring retinal ganglion cells.
  • YAP - (Yes-Associated Protein) transcriptional regulator required for retinal progenitor cell cycle progression and RPE cell fate acquisition. PMID 27616714 OMIM - YAP1
Other Terms Lists  
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Gastrointestinal | Genetic | Hearing | Heart | Immune | Integumentary | Neural | Oocyte | Palate | Placenta | Renal | Respiratory | Spermatozoa | Ultrasound | Vision | Historic | Glossary
 2017 ANAT2341 - Timetable | Course Outline | Group Projects | Moodle | Tutorial 1 | Tutorial 2 | Tutorial 3

Labs: 1 Fertility and IVF | 2 ES Cells to Genome Editing | 3 Preimplantation and Early Implantation | 4 Reproductive Technology Revolution | 5 Cardiac and Vascular Development | 6 CRISPR-Cas9 | 7 Somitogenesis and Vertebral Malformation | 8 Organogenesis | 9 | 10 | 11

Lectures: 1 Introduction | 2 Fertilization | 3 Week 1/2 | 4 Week 3 | 5 Ectoderm | 6 Placenta | 7 Mesoderm | 8 Endoderm | 9 Research Technology | 10 Cardiovascular | 11 Respiratory | 12 Neural crest | 13 Head | 14 Musculoskeletal | 15 Limb | 16 Renal | 17 Genital | 18 Endocrine

 Student Projects: 1 Cortex | 2 Kidney | 3 Heart | 4 Eye | 5 Lung | 6 Cerebellum