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The trilaminar embryo

The top layer of the early trilaminar embryo germ layers (ectoderm, mesoderm and endoderm) formed by gastrulation. The ectoderm can be though of as having 4 early regions: neural plate, neural crest, surface ectoderm and placodes. Note that there are other pages describing neural (central nervous system; brain and spinal cord) and neural crest (peripheral nervous system; sensory and sympathetic ganglia). Epidermis (integumentary, skin contribution) development will be briefly mentioned due to its ectoderm origin.

The ectoderm contributes to the human embryo:

  1. nervous system, both central (neural plate) and peripheral (neural crest).
  2. epidermis of the skin (surface ectoderm) and pigmented cells (neural crest).
  3. head regions that contribution sensory and endocrine structures (placodes).
  4. adrenal gland medullary cells (neural crest).

Ectoderm Links: gastrulation | endoderm | mesoderm | ectoderm | Lecture - Ectoderm Development | Lecture - Neural Development | Lecture - Integumentary Development | neural | neural crest | integumentary | placode | Category:Ectoderm

Some Recent Findings

Frog ectoderm gene co-expression network
Frog ectoderm gene co-expression network[1]
Zebrafish ectodermal patterning model[2]
  • Notch signaling in the division of germ layers in bilaterian embryos[3] "Bilaterian embryos are triploblastic organisms which develop three complete germ layers (ectoderm, mesoderm, and endoderm). While the ectoderm develops mainly from the animal hemisphere, there is diversity in the location from where the endoderm and the mesoderm arise in relation to the animal-vegetal axis, ranging from endoderm being specified between the ectoderm and mesoderm in echinoderms, and the mesoderm being specified between the ectoderm and the endoderm in vertebrates. A common feature is that part of the mesoderm segregates from an ancient bipotential endomesodermal domain. The process of segregation is noisy during the initial steps but it is gradually refined. In this review, we discuss the role of the Notch pathway in the establishment and refinement of boundaries between germ layers in bilaterians, with special focus on its interaction with the Wnt/β-catenin pathway."
  • A molecular atlas of the developing ectoderm defines neural, neural crest, placode, and nonneural progenitor identity in vertebrates[1] "During vertebrate neurulation, the embryonic ectoderm is patterned into lineage progenitors for neural plate, neural crest, placodes and epidermis. Here, we use Xenopus laevis embryos to analyze the spatial and temporal transcriptome of distinct ectodermal domains in the course of neurulation, during the establishment of cell lineages. In order to define the transcriptome of small groups of cells from a single germ layer and to retain spatial information, dorsal and ventral ectoderm was subdivided along the anterior-posterior and medial-lateral axes by microdissections. Principal component analysis on the transcriptomes of these ectoderm fragments primarily identifies embryonic axes and temporal dynamics. This provides a genetic code to define positional information of any ectoderm sample along the anterior-posterior and dorsal-ventral axes directly from its transcriptome. In parallel, we use nonnegative matrix factorization to predict enhanced gene expression maps onto early and mid-neurula embryos, and specific signatures for each ectoderm area. The clustering of spatial and temporal datasets allowed detection of multiple biologically relevant groups (e.g., Wnt signaling, neural crest development, sensory placode specification, ciliogenesis, germ layer specification). We provide an interactive network interface, EctoMap, for exploring synexpression relationships among genes expressed in the neurula, and suggest several strategies to use this comprehensive dataset to address questions in developmental biology as well as stem cell or cancer research."
  • Meis transcription factor maintains the neurogenic ectoderm and regulates the anterior-posterior patterning in embryos of a sea urchin, Hemicentrotus pulcherrimus[4] "Precise body axis formation is an essential step in the development of multicellular organisms, for most of which the molecular gradient and/or specifically biased localization of cell-fate determinants in eggs play important roles. In sea urchins, however, any biased proteins and mRNAs have not yet been identified in the egg except for vegetal cortex molecules, suggesting that sea urchin development is mostly regulated by uniformly distributed maternal molecules with contributions to axis formation that are not well characterized. Here, we describe that the maternal Meis transcription factor regulates anterior-posterior axis formation through maintenance of the most anterior territory in embryos of a sea urchin, Hemicentrotus pulcherrimus. Loss-of-function experiments revealed that Meis is intrinsically required for maintenance of the anterior neuroectoderm specifier foxQ2 after hatching and, consequently, the morphant lost anterior neuroectoderm characteristics. In addition, the expression patterns of univin and VEGF, the lateral ectoderm markers, and the mesenchyme-cell pattern shifted toward the anterior side in Meis morphants more than they did in control embryos, indicating that Meis contributes to the precise anteroposterior patterning by regulating the anterior neuroectodermal fate.
More recent papers  
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  • The displayed list of references do not reflect any editorial selection of material based on content or relevance.
  • References also appear on this list based upon the date of the actual page viewing.

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.

More? References | Discussion Page | Journal Searches | 2019 References | 2020 References

Search term: Ectoderm Development | Images | Ectoderm

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • A BMP regulatory network controls ectodermal cell fate decisions at the neural plate border.[2] "During ectodermal patterning the neural crest and preplacodal ectoderm are specified in adjacent domains at the neural plate border. BMP signalling is required for specification of both tissues, but how it is spatially and temporally regulated to achieve this is not understood. Here, using a transgenic zebrafish BMP reporter line in conjunction with double-fluorescent in situ hybridisation, we show that, at the beginning of neurulation, the ventral-to-dorsal gradient of BMP activity evolves into two distinct domains at the neural plate border: one coinciding with the neural crest and the other abutting the epidermis. In between is a region devoid of BMP activity, which is specified as the preplacodal ectoderm. We identify the ligands required for these domains of BMP activity. We show that the BMP-interacting protein Crossveinless 2 is expressed in the BMP activity domains and is under the control of BMP signalling. We establish that Crossveinless 2 functions at this time in a positive-feedback loop to locally enhance BMP activity, and show that it is required for neural crest fate. We further demonstrate that the Distal-less transcription factors Dlx3b and Dlx4b, which are expressed in the preplacodal ectoderm, are required for the expression of a cell-autonomous BMP inhibitor, Bambi-b, which can explain the specific absence of BMP activity in the preplacodal ectoderm. Taken together, our data define a BMP regulatory network that controls cell fate decisions at the neural plate border."
<html5media width='316' height='500' image="">File:Neuralplate_001.mp4</html5media> This animation shows the embryonic disc from the amniotic cavity side ectoderm (human week 3) onward.
  • Neural plate (blue) in central region of the ectoderm.
  • Primitive streak extending from the bottom of the neural plate.
  • Epidermis primordia (white) region surrounding the neural plate. Integumentary (skin) development will be briefly covered here.
  • Buccopharnygeal and Cloacal membranes (circular region above and below the neural plate).

Stage10 neural sm.jpg Stage10 SEM1.jpg


  • Understanding of events during the third and fourth week of development
  • Understanding the process of notochord formation
  • Understanding the process of early neural development
  • Brief understanding of neural crest formation
  • Brief understanding of epidermis formation
  • Understanding of the adult components derived from ectoderm
  • Brief understanding of early neural abnormalities

Textbook References

  • Human Embryology (3rd ed.) Chapter 5 p107-125
  • The Developing Human: Clinically Oriented Embryology (6th ed.)
  • Moore and Persaud Chapter 18 p451-489
  • Essentials of Human Embryology Larson Chapter 5 p69-79
  • Before We Are Born (5th ed.) Moore and Persaud Chapter 19 p423-458


The nested tables below show an overview of the different ectoderm-derived tissues (links go to topic pages).
Template Only - content to be added. Mesoderm has been completed.
neural plate  
neural tube
central nervous system - brain, spinal cord
neural crest 
neural crest
otic - inner ear cochlea, vestibular optic - lens nasal anterior pituitary
surface ectoderm  
integumentary - epithelium, glands
placental membrane
Overview: Ectoderm | Mesoderm | Endoderm Layers: ectoderm | mesoderm | endoderm

Ectoderm Structures  
Ectoderm Origin
Alphabetical list of anatomical structures derived from ectoderm.
  • abdominal histoblast anlage
  • acinus of lacrimal gland
  • acinus of lactiferous gland
  • acinus of olfactory gland
  • acinus of sebaceous gland
  • actinotrichium
  • adenohypophysis pituitary
  • adult clypeo-labral anlage
  • afterfeather (avian)
  • ala of nose
  • alar plate midbrain (mesencephalon)
  • ampullary organ
  • anal canal
  • anal column
  • anal sac
  • anal-fin hook
  • anterior dentation of pectoral fin spine (zebrafish)
  • anterior distal serration of pectoral fin spine (zebrafish)
  • anterior ectoderm derivative
  • anterior ectodermal midgut
  • anterior lamina recurvata
  • anterior neural keel
  • anterior neural rod
  • anterior presumptive neural plate
  • anterior ramus of cleithrum
  • anterior segment of eyeball
  • anterior uvea
  • anterolateral process of frontoparietal
  • anteroventral process of cleithrum
  • anus
  • apex of cochlea
  • aqueous drainage system
  • aqueous vein
  • areola
  • areolar tubercle
  • arista
  • arrector pili muscle of vibrissa
  • arthropod optic lobe
  • ascending process of the parasphenoid
  • base of cochlear canal
  • basilar membrane of cochlea
  • basilar papilla
  • basipterygoid process of parasphenoid
  • basis modioli
  • blood-cerebrospinal fluid barrier
  • blood-inner ear barrier
  • Bolwig organ
  • bony labyrinth
  • brain
  • brain blood vessel
  • brain ventricle/choroid plexus
  • bulb of hair follicle
  • calcareous tooth
  • calcified structure of brain
  • camera-type eye
  • canal of Schlemm
  • canthus
  • capsule of lens
  • cardiac neural crest
  • cartilage of external acoustic meatus
  • cartilaginous external acoustic tube
  • caudal mesencephalo-cerebellar tract
  • caudal-fin hook
  • central canal of spinal cord
  • central figure of scute
  • central nervous system (neural)
  • cephalopod optic lobe
  • cerebellar crest
  • cerebral hemisphere
  • cerebral subcortex
  • chamber of eyeball
  • chitin-based cuticle
  • chorioretinal region
  • choroid plexus stroma
  • ciliary body
  • ciliary marginal zone
  • ciliary processes
  • ciliary stroma
  • circuit part of central nervous system
  • cleithrum head
  • climbing fiber
  • clypeus
  • cochlea
  • cochlear basement membrane
  • cochlear canal
  • cochlear duct of membranous labyrinth
  • cochlear labyrinth
  • cochlear modiolus
  • collagenous dermal stroma
  • columella nasi
  • common crus
  • common crus of semicircular duct
  • conjunctiva
  • conjunctival papilla
  • conjunctival sac
  • corneo-scleral junction
  • corpora quadrigemina
  • cortex of hair
  • courtship gland
  • cranial neural crest
  • crista ampullaris
  • crus commune
  • ctenius
  • cultriform process
  • cusp of tooth
  • cutaneous elastic tissue
  • cutaneous microfibril
  • cuticle of hair
  • cuticular specialization
  • dartos muscle of labia majora
  • dentate gyrus subgranular zone
  • dermal condensation of feather follicle
  • dermal papilla
  • dermal pulp of feather shaft (avian)
  • dermal scale focus
  • dermal skeletal element
  • dermal superficial region
  • dermis
  • dermis of feather follicle (avian)
  • diaphragma sellae
  • diencephalic part of interventricular foramen
  • distal limb integumentary appendage
  • dorsal ectoderm derivative
  • dorsal mesothorax
  • dorsal part of optic cup
  • dorsal zone of medial entorhinal cortex
  • dorso-rostral cluster
  • dorsolateral septum
  • dorsum of nose
  • duct of apocrine sweat gland
  • duct of eccrine sweat gland
  • duct of olfactory gland
  • duct of sebaceous gland
  • ductus reuniens
  • dura mater lymph vessel
  • ecto-epithelium
  • ectodermal part of digestive tract
  • Eimer's organ
  • elastica externa of notochord
  • enamel knot
  • endolymphatic duct
  • endolymphatic system
  • entorhinal cortex
  • epibranchial ganglion
  • epidermal egg tooth (avian)
  • epidermal intermediate stratum
  • epidermal placode
  • epidermal ridge of digit
  • epidermal scale
  • epidermal superficial stratum
  • epidermal-dermal junction
  • epidermis of feather follicle
  • epidermis suprabasal layer
  • epioccipital bridge
  • epioccipital posterior process
  • epiotic
  • epiphysial cluster
  • Template:External acoustic meatus
  • external acoustic meatus osseus part
  • external cellular layer
  • external naris
  • external nose
  • eye muscle
  • eye trabecular meshwork
  • eyeball of camera-type eye
  • eyelid
  • eyelid blood vessel
  • eyelid gland
  • falx cerebelli
  • falx cerebri
  • fasciolar gyrus
  • feather (avian)
  • feather barb (avian)
  • feather barbicel (avian)
  • feather barbule (avian)
  • feather bud, dermal component (avian)
  • feather calamus (avian)
  • feather shaft (avian)
  • feather vane (avian)
  • filum terminale
  • filum terminale externum
  • filum terminale internum
  • fin fold pectoral fin bud
  • flexural organ
  • floor plate
  • floor plate of neural tube
  • foramen cecum of frontal bone
  • forebrain neural keel
  • forebrain neural rod
  • forebrain neural tube
  • forebrain-midbrain boundary
  • foregut duodenum mesentery
  • fourth ventricle aperture
  • fovea centralis
  • foveola of retina
  • future hindbrain meninx
  • ganglion of central nervous system
  • gelatinous layer of statoconial membrane
  • gigantocellular part of magnocellular preoptic nucleus
  • glabella region of bone
  • gland of anal canal
  • gland of anal sac
  • gland of diencephalon
  • gland of nasal mucosa
  • granular layer corpus cerebelli
  • granular layer valvula cerebelli
  • gyrus
  • hair canal
  • hair matrix
  • hair medulla
  • hair root
  • hair root sheath
  • hair root sheath matrix
  • hair shaft
  • Harderian gland
  • Harderian gland duct
  • head taste bud
  • helicotrema
  • Hensen stripe
  • hindbrain neural keel
  • hindbrain neural rod
  • hindbrain neural tube
  • hindbrain venous system
  • hindbrain-spinal cord boundary
  • hoof lamina
  • hyoid articular area
  • hypocleideum
  • immature otolith
  • inferior branch of oculomotor nerve
  • inferior horn of the lateral ventricle
  • inferior parietal cortex
  • inferior rectal artery
  • infundibular organ
  • infundibulum of hair follicle
  • inner ear foramen
  • internal acoustic meatus
  • internal cellular layer
  • internal ear
  • internal surface of frontal bone
  • interventricular foramen of CNS
  • iris
  • iris stroma
  • isthmus of cingulate gyrus
  • Kimura membrane
  • labyrinthine artery
  • lacrimal apparatus
  • lacrimal canaliculus
  • lacrimal drainage system
  • lacrimal gland
  • lacrimal lake
  • lacrimal papilla
  • lacrimal punctum
  • lacrimal sac
  • lamina inferior
  • lamina nariochoanalis
  • lamina of spiral limbus
  • lateral eminence of fourth ventricle
  • lateral eminence of hypophysis
  • lateral entorhinal cortex
  • lateral floor plate
  • lateral line
  • lateral line ganglion
  • lateral ventricle subependymal layer
  • lateral wall neural rod
  • lateral zone of hypothalamus
  • layer of dura mater
  • layer of hippocampal field
  • lens cortex
  • lens fiber
  • lens nucleus
  • lens of camera-type eye
  • lens vesicle
  • lepidotrichial segment
  • limbic system
  • limiting layer of elasmoid scale
  • lobe of cerebral hemisphere
  • lobule of mammary gland
  • lunule of nail
  • macula
  • macula lutea
  • macula lutea proper
  • mammary gland
  • mammary gland alveolus
  • mammary gland connective tissue
  • mammary gland smooth muscle
  • mammary lobe
  • mammillary body
  • mandibular arch neural crest
  • margin of eyelid
  • margo anterior of cleithrum
  • margo posterior of cleithrum
  • margo scapularis
  • margo vertebralis
  • medial entorhinal cortex
  • medial floor plate
  • medial zone of hypothalamus
  • median pars intermedia
  • medulla oblongata
  • membranous labyrinth
  • meninx
  • mesenchyme of mammary gland
  • mesothoracic tergum
  • metotic fissure
  • midbrain neural keel
  • midbrain neural rod
  • midbrain neural tube
  • midbrain-hindbrain boundary
  • midgut duodenum mesentery
  • mixed ectoderm/mesoderm/endoderm-derived structure
  • mole
  • molecular layer corpus cerebelli
  • molecular layer valvula cerebelli
  • mossy fiber
  • mucosa of anal canal
  • mucosa of lacrimal canaliculus
  • mucosa of nasolacrimal duct
  • muscle layer of anal canal
  • nail matrix
  • nail plate
  • nasal bridge
  • nasal cartilage
  • nasal cavity mucosa
  • nasal muscle
  • nasal tentacle
  • naso-frontal vein
  • nasolabial region
  • nasolacrimal duct
  • neck of tooth
  • neural crest
  • neural crest-derived structure
  • neural tube basal plate
  • neural tube lateral wall
  • neuraxis flexure
  • neurectoderm
  • neurogenic field
  • neuromast
  • neuromere
  • neuropore
  • nipple
  • non-neural ectoderm
  • nose
  • nose anterior margin
  • nose vertex
  • notochord
  • notochord posterior region
  • notochordal canal
  • nucleus pulposus
  • nuptial pad
  • ocular fundus
  • ocular surface region
  • olfactory apparatus chamber
  • olivary body
  • opercular part of inferior frontal gyrus
  • opisthotic
  • optic cup
  • optic disc
  • optic fissure
  • optic pit
  • optic vesicle
  • ora serrata of retina
  • orbital part of frontal bone
  • oronasal membrane
  • osseus cochlear canal
  • osseus labyrinth vestibule
  • osseus semicircular canal
  • osseus spiral lamina
  • otic capsule
  • otic vesicle protrusion
  • otolith
  • otolith organ
  • otolithic part of statoconial membrane
  • outer root sheath companion layer
  • palpebral fissure
  • papillary layer of dermis
  • parafoveal part of retina
  • parallel fiber
  • parapineal organ
  • parasagittal crest
  • parasphenoid flange
  • parenchyma of central nervous system
  • parenchyma of mammary gland
  • parietal organ
  • pars amphibiorum
  • pars basilaris
  • pars inferior of labyrinth
  • pars intermedia of adenohypophysis
  • pars plana of ciliary body
  • pars plicata of ciliary body
  • pars tuberalis of adenohypophysis
  • pectinate line
  • pectoral fin fold
  • pectoral fin hook
  • pelvic fin hook
  • perichordal ring
  • perichordal tissue
  • perifoveal part of retina
  • perilymphatic channel
  • perilymphatic system
  • periocular mesenchyme
  • peripheral region of retina
  • periventricular zone of hypothalamus
  • pillar of the semicircular canal
  • pineal foramen
  • pit organ
  • placodal ectoderm
  • plica semilunaris of conjunctiva
  • podotheca
  • pole of lens
  • pontine tegmentum
  • postbranchial lamina
  • posterior cleithral process
  • posterior dentation of dorsal fin spine 2
  • posterior dentation of pectoral fin spine
  • posterior lamina recurvata
  • posterior lateral line primordium
  • posterior neural keel
  • posterior neural rod
  • posterior presumptive neural plate
  • posterior ramus of cleithrum
  • posterior segment of eyeball
  • postorbital process
  • pre-Botzinger complex
  • pre-chordal neural plate
  • presubiculum
  • presumptive arista
  • presumptive prothoracic metatarsus
  • primary choana
  • primary olfactory fiber layer
  • primary vitreous
  • primitive superior sagittal sinus
  • proboscis
  • processus posterior of parasphenoid
  • procurrent spur
  • prootic bone
  • prothoracic leg
  • prothoracic tarsal segment
  • protocerebrum
  • pupillary membrane
  • Purkinje cell layer corpus cerebelli
  • Purkinje cell layer valvula cerebelli
  • ramus anterior of CN VIII
  • ramus nasalis medialis
  • ramus of feather barb
  • ramus of feather barbule
  • ramus posterior of CN VIII
  • recessus basilaris
  • recessus fenestrae ovalis
  • regional part of brain
  • regional part of spinal cord
  • Reissner's fiber
  • remnant of Rathke's pouch
  • reticular layer of dermis
  • reticular membrane of spiral organ
  • retina
  • retrochiasmatic area
  • rhamphotheca
  • rhinarium
  • rhombomere boundary
  • ridge of tooth
  • roof plate
  • roof plate of diencephalon
  • roof plate of medulla oblongata
  • roof plate of metencephalon
  • roof plate of midbrain
  • roof plate of telencephalon
  • roof plate spinal cord region
  • root of nail
  • saccule duct
  • saccus dorsalis
  • sacral neural crest
  • sallet
  • scale primordium
  • segmental subdivision of hindbrain
  • semicircular canal
  • semicircular canal ampulla
  • semicircular duct
  • sensory dissociation area
  • septal olfactory organ
  • septum pellucidum
  • septum semicircularium anterior
  • septum semicircularium laterale
  • septum semircularium posterior
  • skeletal muscle tissue of eye
  • skin appendage follicle
  • skin crease
  • skin gland
  • skin of body
  • smooth muscle of eye
  • spatium sacculare
  • spina acromioidea
  • spinal cord
  • spinal cord neural keel
  • spinal cord neural rod
  • spinal cord neural tube
  • spiral ligament
  • spiral modiolar artery
  • spiral organ of cochlea
  • spiral prominence of cochlear duct
  • statoconial membrane
  • stomatogastric nervous system
  • strand of hair
  • stratum basale of epidermis
  • stratum compactum of dermis
  • stratum fibrosum et griseum superficiale
  • stratum granulosum of epidermis
  • stratum intermedium of epidermis
  • stratum intermedium of tooth
  • stratum lucidum of epidermis
  • stratum marginale
  • stratum opticum
  • stratum periventriculare
  • stratum spinosum of epidermis
  • stria vascularis of cochlear duct
  • stylar shelf
  • subcupular meshwork of statoconial membrane
  • subdivision of conjunctiva
  • subdivision of spinal cord central canal
  • submucosa of anal canal
  • subolfactory process
  • subotic alae
  • substantia nigra pars compacta
  • substantia nigra pars reticulata
  • sulcus limitans of neural tube
  • sulcus ypsiloniformis
  • supcapsular region of anterior region of lens
  • supcapsular region of posterior region of lens
  • superior branch of oculomotor nerve
  • superior parietal cortex
  • supraorbital flange
  • suspensory ligament of breast
  • suspensory ligament of lens
  • synaptic neuropil
  • synaptic neuropil block
  • tapetum lucidum of camera-type eye
  • tectorial membrane of cochlea
  • tectorial restraint system
  • tela choroidea of fourth ventricle
  • tela choroidea of midbrain cerebral aqueduct
  • tela choroidea of telencephalic ventricle
  • tela choroidea of third ventricle
  • telencephalic part of interventricular foramen
  • tentorium cerebelli
  • tergite
  • terminal part of the cochlear canal
  • tooth crown
  • tooth enamel organ
  • tooth root
  • triangular part of inferior frontal gyrus
  • trunk neural crest
  • trunk taste bud
  • tunica fibrosa of eyeball
  • type 1 odontode
  • upper eyelid protuberances
  • urohyal lateral process
  • urohyal median process
  • urophysis
  • utricle duct
  • utricle valve
  • utriculosaccular duct
  • uvea
  • vacuolated notochordal tissue
  • vagal neural crest
  • vallecula of cerebellum
  • vein of vestibular aqueduct
  • venous dural sinus
  • venous system of brain
  • ventral ectoderm derivative
  • ventral limb of posttemporal
  • ventral part of optic cup
  • ventral sulcus
  • ventricular system of brain
  • ventricular system of central nervous system
  • Verson's gland
  • vestibular aqueduct
  • vestibular fissure of the cochlear canal
  • vestibular labyrinth
  • vestibular membrane of cochlear duct
  • vitreous body
  • vomeronasal organ
  • zone of basilar membrane of cochlea
  • zone of skin
  • zygomatic process of frontal bone
Data Origin: Bioportal Uberon is an integrated cross-species anatomy ontology representing a variety of entities classified according to traditional anatomical criteria such as structure, function and developmental lineage.  

Links: ectoderm | Ectoderm table | Ectoderm collapse table | Neural Crest table | Mesoderm table | Endoderm table


  • forms initially as the Axial Process, a hollow tube which extends from the primitive pit , cranially to the oral membrane
  • the axial process then allow transient communication between the amnion and the yolk sac through the neuroenteric canal.
  • the axial process then merges with the Endodermal layer to form the Notochordal Plate.
  • the notochordal plate then rises back into the Mesodermal layer as a solid column of cells which is the Notochord.


  • 2 parts
  • midline neural plate
    • columnar
  • lateral surface ectoderm
    • cuboidal
    • sensory placodes
    • epidermis of skin, hair, glands, anterior pituitary, teeth enamel

Neural Plate

Neuralplate cartoon.png
Stage 10 neural groove to tube
<html5media height="500" width="316">File:Neuralplate_001.mp4</html5media>

Click Here to play on mobile device

Development of the neural plate region at the embryonic disc stage.

Dorsal view of the embryonic disc from the amniotic cavity side showing the ectoderm with the central region developing into the neural plate.

The neural plate extends from buccopharyngeal membrane to primitive node and forms above the notochord and paraxial mesoderm.The neuroectodermal cells form a broad brain plate and narrower spinal cord region.

Three specific regions medial to lateral can also be identified: midline region floor plate, neural plate, edge of neural plate neural crest

  • extends from buccopharyngeal membrane to primitive node
  • forms above notochord and paraxial mesoderm
  • neuroectodermal cells
    • broad brain plate
    • narrower spinal cord
  • 3 components form: floor plate, neural plate, neural crest

Neural Determination- neuronal populations are specified before plate folds

  • signals from notochord and mesoderm - secrete noggin, chordin,follistatin
    • all factors bind BMP-4 an inhibitor of neuralation
    • bone morphogenic protein acts through membrane receptor
  • lateral inhibition generates at spinal cord level 3 strips of cells
  • expression of delta inhibits nearby cells, which express notch receptor, from becoming neurons
  • Delta-Notch inetraction- generates Neural strips

Neural Groove

<html5media height="480" width="480">File:Neuraltube_001.mp4</html5media>

Click Here to play on mobile device

This animation of early neural development from week 3 onward shows the neural groove fusing to form the neural tube.

View - Dorsolateral of the whole early embryo and yolk sac. Cranial (head) to top and caudal (tail) to bottom. Yolk sac is shown to the left.

Beginning with the neural groove initially fusing at the level of the 4th somite to form the neural tube and closing in both directions to leave 2 openings or neuropores: a cranial neuropore (anterior neuropore) and a caudal neuropore (posterior neuropore).

The animation also shows as the embryo grows and folds it increases in size relative to the initial yolk sac. Note also the increasing number of somites over time.

  • forms in the midline of the neural plate (day 18-19)
  • either side of which are the neural folds which continues to deepen until about week 4
  • neural folds begins to fuse, beginning at 4th somite level

Neural Tube

Stage 12 caudal neuropore
  • the neural tube forms the brain and spinal cord
  • fusion of neural groove extends rostrally and caudally
  • begins at the level of 4th somite
  • closes neural groove "zips up" in some species.
    • humans appear to close at multiple points along the tube.
  • leaves 2 openings at either end - Neuropores
    • cranial neuropore closes before caudal

Failure for the neural tube to close correctly or completely results in a neural tube defect.

Secondary Neuralation

<html5media height="300" width="320">File:Secondary_neurulation_01.mp4</html5media>

Click Here to play on mobile device

This animation shows the early developmental process often described as secondary neurulation.

Red - site of secondary neurulation | Blue - neural tube

  • caudal end of neural tube formed by secondary neuralation
  • develops from primitive streak region
  • solid cord canalized by extension of neural canal
  • mesodermal caudal eminence
Links: MP4 version | Neural System Development

Neural Crest

  • a population of cells at the edge of the neural plate that lie dorsally when the neural tube fuses
    • dorsal to the neural tube, as a pair of streaks
    • pluripotential, forms many different types of cells
    • cells migrate throughout the embryo
    • studied by quail-chick chimeras
    • transplanted quail cells have obvious nucleoli compared with chicken

Neural Crest Derivitives

  • dorsal root ganglia
  • autonomic ganglia
  • adrenal medulla
  • drg sheath cells, glia
  • pia-arachnoid sheath
  • skin melanocytes
  • connective tissue of cardiac outflow
  • thyroid parafollicular cells
  • craniofacial skeleton
  • teeth odontoblasts
Links: Neural Crest Development

Ectodermal Placodes

  • Specialized ectodermal "patches" in the head region
  • Contribute sensory structures - otic placode (otocyst), nasal placode, lens placode
  • Contribute teeth

Human Neuralation - Early Stages

The stages below refer to specific Carneigie stages of development.

  • Carnegie stage 8 (about 18 postovulatory days) neural groove and folds are first seen
  • Carnegie stage 9 the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open.
  • Carnegie stage 10 (two days later) neural folds begin to fuse near the junction between brain and spinal cord, when neural crest cells are arising mainly from the neural ectoderm
  • Carnegie stage 11 (about 24 days) the rostral (or cephalic) neuropore closes within a few hours; closure is bidirectional, it takes place from the dorsal and terminal lips and may occur in several areas simultaneously. The two lips, however, behave differently.
  • Carnegie stage 12 (about 26 days) The caudal neuropore takes a day to close.
    • the level of final closure is approximately at future somitic pair 31
    • corresponds to the level of sacral vertebra 2
  • Carnegie stage 13 (4 weeks) the neural tube is normally completely closed.

Secondary neurulation begins at stage 12 - is the differentiation of the caudal part of the neural tube from the caudal eminence (or end-bud) without the intermediate phase of a neural plate.

Above text modified from[5]


Neural Development
Neuralplate 001 icon.jpg
 ‎‎Neural Plate
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Neuraltube 001 icon.jpg
 ‎‎Neural Tube
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 ‎‎Secondary Neurulation
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 ‎‎Stage 13 Neural
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 ‎‎Embryo CNS
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 ‎‎Neural Tube Close
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Stage16 MRI 3D02 icon.jpg
 ‎‎Embryo CNS
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 ‎‎Embryo Stage 16
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 ‎‎Stage 17 Embryo
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 ‎‎Stage 22 Neural
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 ‎‎Embryo CNS
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 ‎‎Sagittal Head
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Abnormalities Ultrasound
Brain fissure development 03.jpg
 ‎‎Sylvian Fissure
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 ‎‎Adult Brain
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US Dandy-Walker 01.jpg
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US Spina bifida GA19week.jpg
 ‎‎Spina Bifida
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  1. 1.0 1.1 Plouhinec JL, Medina-Ruiz S, Borday C, Bernard E, Vert JP, Eisen MB, Harland RM & Monsoro-Burq AH. (2017). A molecular atlas of the developing ectoderm defines neural, neural crest, placode, and nonneural progenitor identity in vertebrates. PLoS Biol. , 15, e2004045. PMID: 29049289 DOI.
  2. 2.0 2.1 Reichert S, Randall RA & Hill CS. (2013). A BMP regulatory network controls ectodermal cell fate decisions at the neural plate border. Development , 140, 4435-44. PMID: 24089471 DOI.
  3. Favarolo MB & López SL. (2018). Notch signaling in the division of germ layers in bilaterian embryos. Mech. Dev. , 154, 122-144. PMID: 29940277 DOI.
  4. Yaguchi J, Yamazaki A & Yaguchi S. (2018). Meis transcription factor maintains the neurogenic ectoderm and regulates the anterior-posterior patterning in embryos of a sea urchin, Hemicentrotus pulcherrimus. Dev. Biol. , 444, 1-8. PMID: 30266259 DOI.
  5. <pubmed>8005032</pubmed>


Online Textbooks


Search NLM Online Textbooks: "Ectoderm" : Developmental Biology | The Cell- A molecular Approach | Molecular Biology of the Cell


Kutejova E, Briscoe J & Kicheva A. (2009). Temporal dynamics of patterning by morphogen gradients. Curr. Opin. Genet. Dev. , 19, 315-22. PMID: 19596567 DOI.

Charron F & Tessier-Lavigne M. (2007). The Hedgehog, TGF-beta/BMP and Wnt families of morphogens in axon guidance. Adv. Exp. Med. Biol. , 621, 116-33. PMID: 18269215 DOI.

Charron F & Tessier-Lavigne M. (2005). Novel brain wiring functions for classical morphogens: a role as graded positional cues in axon guidance. Development , 132, 2251-62. PMID: 15857918 DOI.

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.

Take the Quiz

1 Ectoderm refers only to the neural plate region of the trilaminar embryo


2 The central nervous system forms in the sequence:

norochord to neural plate to neural tube
neural tube to neural plate to neural groove
neural plate to neural groove to neural tube
neural plate to neural crest to neural zone

3 The neural plate is narrower at the caudal (tail) end and therefore closes earlier than the broad cranial (head) end.


4 The correct sequence from cranial to caudal of the secondary brain vesicles is:

prosencephalon, mesencephalon, metencephalon, myelencephalon, rhombencephalon
telencephalon, diencephalon, metencephalon, mesencephalon, myelencephalon
telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon
prosencephalon, diencephalon, mesencephalon, myelencephalon, metencephalon

Glossary Links

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Cite this page: Hill, M.A. (2024, May 25) Embryology Ectoderm. Retrieved from

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