Ectoderm

ectodermalectodermal tissuesEmbryonic ectodermectodermaectodermal cellneural ectoderm
Ectoderm is one of the three primary germ layers in the very early embryo.wikipedia
304 Related Articles

Germ layer

germ layersmesodermectoderm
Ectoderm is one of the three primary germ layers in the very early embryo. Heinz Christian Pander, a Baltic German–Russian biologist, has been credited for the discovery of the three germ layers that form during embryogenesis.
Some animals, like cnidarians, produce two germ layers (the ectoderm and endoderm) making them diploblastic.

Endoderm

endodermalEntodermdefinitive endoderm
The other two layers are the mesoderm (middle layer) and endoderm (most proximal layer), with the ectoderm as the most exterior (or distal) layer.
The other two layers are the ectoderm (outside layer) and mesoderm (middle layer), with the endoderm being the innermost layer.

Mesoderm

mesodermalmiddle cell layerparietal layer
The other two layers are the mesoderm (middle layer) and endoderm (most proximal layer), with the ectoderm as the most exterior (or distal) layer.
The other two layers are the ectoderm (outside layer) and endoderm (inside layer), with the mesoderm as the middle layer between them.

Neural crest

neural crest cellsneural crest cellcrest
In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube. The neural tube cells will become the central nervous system, neural crest cells will become the peripheral and enteric nervous system, along with melanocytes, facial cartilage and the dentin of teeth, and the epidermal cell region will give rise to epidermis, hair, nails, sebaceous glands, olfactory and mouth epithelium, as well as eyes.
Neural crest cells are a temporary group of cells unique to chordates of the group Cristozoa that arise from the embryonic ectoderm cell layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia.

Embryo

embryosembryonalhuman embryos
Ectoderm is one of the three primary germ layers in the very early embryo. Once there is an embryo with three established germ layers, differentiation among these three layers proceeds.
During gastrulation of triploblastic animals, the three germinal layers that form are called the ectoderm, mesoderm, and endoderm.

Neuroectoderm

Neural ectodermneurectodermneuro-ectodermal
The latter two are known as neuroectoderm. The epidermis of the skin originates from the less dorsal ectoderm which surrounds the neuroectoderm at the early gastrula stage of embryonic development.
Neuroectoderm (or neural ectoderm or neural tube epithelium) consists of cells derived from ectoderm.

Neural tube

neural canalneural canalsdorsal neural tube
In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube. The neural tube cells will become the central nervous system, neural crest cells will become the peripheral and enteric nervous system, along with melanocytes, facial cartilage and the dentin of teeth, and the epidermal cell region will give rise to epidermis, hair, nails, sebaceous glands, olfactory and mouth epithelium, as well as eyes.
The ectodermal wall of the tube forms the rudiment of the nervous system.

Nervous system

neuralnervousneurogenic
Generally speaking, the ectoderm differentiates to form the nervous system (spine, peripheral nerves and brain), tooth enamel and the epidermis (the outer part of integument).
Unlike bilaterians, radiata only have two primordial cell layers, endoderm and ectoderm.

Embryonic development

embryogenesisdevelopmentembryo development
Heinz Christian Pander, a Baltic German–Russian biologist, has been credited for the discovery of the three germ layers that form during embryogenesis. The epidermis of the skin originates from the less dorsal ectoderm which surrounds the neuroectoderm at the early gastrula stage of embryonic development.
The egg cell is generally asymmetric, having an "animal pole" (future ectoderm and mesoderm) and a "vegetal pole" (future endoderm).

Skin

cutaneousskin cellanimal skin
The epidermis of the skin originates from the less dorsal ectoderm which surrounds the neuroectoderm at the early gastrula stage of embryonic development.
In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs.

Gastrulation

gastrulablastoporedorsal lip
The ectoderm can first be observed in amphibians and fish during the later stages of a process called gastrulation.
These three germ layers are known as the ectoderm, mesoderm, and endoderm.

Epiboly

Once convergent extension and radial intercalation are underway, the rest of the vegetal pole, which will become endoderm cells, is completely engulfed by the prospective ectoderm, as these top cells undergo epiboly, where the ectoderm cells divide in a way to form one layer.
At this point the zebrafish embryo contains three portions: an epithelial monolayer known as the enveloping layer (EVL), a yolk syncytial layer (YSL) which is a membrane-enclosed group of nuclei that lie on top of the yolk cell, and the deep cells (DEL) of the blastoderm which will eventually form the embryo's three germ layers (ectoderm, mesoderm, and endoderm).

Tooth

teethdentalmaxillary teeth
The neural tube cells will become the central nervous system, neural crest cells will become the peripheral and enteric nervous system, along with melanocytes, facial cartilage and the dentin of teeth, and the epidermal cell region will give rise to epidermis, hair, nails, sebaceous glands, olfactory and mouth epithelium, as well as eyes.
The cellular tissues that ultimately become teeth originate from the embryonic germ layer, the ectoderm.

Karl Ernst von Baer

Karl BaerBaerKarl von Baer
Pander's work of the early embryo was continued by a Prussian–Estonian biologist named Karl Ernst von Baer.
Together with Heinz Christian Pander and based on the work by Caspar Friedrich Wolff, he described the germ layer theory of development (ectoderm, mesoderm, and endoderm) as a principle in a variety of species, laying the foundation for comparative embryology in the book Über Entwickelungsgeschichte der Thiere (1828).

Cellular differentiation

differentiationcell differentiationdifferentiate
Once there is an embryo with three established germ layers, differentiation among these three layers proceeds.

Blastula

blastulationblastula stage
Baer also received credit for the discovery of the blastula.
The animal cap forms the roof of the blastocoele and goes on primarily to form ectodermal derivatives.

Organogenesis

developmental anatomydevelopmentalform distinct organs
Several signals mediate the organogenesis of the ectoderm such as: FGF, TGFβ, Wnt, and regulators from the hedgehog family.
During organogenesis, the three germ layers formed from gastrulation: the ectoderm, endoderm, and mesoderm form the internal organs of the organism.

Surface ectoderm

external ectoderm
In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube.

Ectodermal dysplasia

ectodermal dysplasiasPure hair–nail type of ectodermal dysplasiaDermal dysplasia
Ectodermal dysplasia is a rare but severe condition where the tissue groups (specifically teeth, skin, hair, nails and sweat glands) derived from the ectoderm undergo abnormal development.
Ectodermal dysplasia (ED) is not a single disorder but a group of genetic syndromes all deriving from abnormalities of the ectodermal structures.

Neural plate

medullary plate
During primary neurulation, the notochord cells of the mesoderm signal the adjacent, superficial ectoderm cells to reposition themselves in a columnar pattern to form cells of the ectodermal neural plate.
In primary neurulation, the layer of ectoderm divides into three sets of cells: the neural tube (future brain and spinal cord), epidermis (skin), and neural crest cells (connects epidermis and neural tube and will migrate to make neurons, glia, and skin cell pigmentation).

Blastocoel

blastocoeleblastoceleblastocoelom
Once this lip has been established, the bottle cells will extend inward and migrate along the inner wall of the blastula known as the roof of the blastocoel.
For instance, the blastocoel prevents the vegetal cells destined to become endoderm from coming in contact with those cells in the ectoderm fated to give rise to the skin and nerves.

List of human cell types derived from the germ layers

This is a list of cells in humans derived from the three germ layers – ectoderm, mesoderm, and endoderm.

Ectoderm specification

Ectodermin
In Xenopus laevis, the specification of the three germ layers (endoderm, mesoderm and ectoderm) occurs at the blastula stage.

Coelom

coelomic fluidacoelomatepseudocoelomate
The archenteron initially forms, and the mesoderm splits into two layers: the first attaches to the body wall or ectoderm, forming the parietal layer and the second surrounds the endoderm or alimentary canal forming the visceral layer.

Ectodysplasin A

EDAEDA1
Most patients carry variants of the X-chromosomal EDA gene.
Ectodysplasin A is a transmembrane protein of the TNF family which plays an important role in the development of ectodermal tissues such as skin in humans.