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The surface ectoderm, AKA external ectoderm, is one of the two early embryonic divisions of the ectoderm. The other early division of the ectoderm is the neuroectoderm. The surface ectoderm develops into the following structures: Skin (only the epidermis; the dermis is derived from the mesoderm) (along with glands, hair, and nails)
The position of the ectoderm relative to the other germ layers of the embryo is governed by "selective affinity", meaning that the inner surface of the ectoderm has a strong (positive) affinity for the mesoderm, and a weak (negative) affinity for the endoderm layer. [6] This selective affinity changes during different stages of development.
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The ectoderm generates the outer layer of the embryo, and it forms from the embryo's epiblast. [13] The ectoderm develops into the surface ectoderm, neural crest, and the neural tube. [14] The surface ectoderm develops into: epidermis, hair, nails, lens of the eye, sebaceous glands, cornea, tooth enamel, the epithelium of the mouth and nose.
Surface ectoderm forms the lens, corneal epithelium and eyelid. The extracellular mesenchyme forms the sclera , the corneal endothelium and stroma , blood vessels , muscles , and vitreous . The eye begins to develop as a pair of optic vesicles on each side of the forebrain at the end of the fourth week of pregnancy.
Mesoderm cells condense to form a rod which will send out signals to redirect the ectoderm cells above. This fold along the neural tube sets up the vertebrate central nervous system. The endoderm is the inner most germ layer of the embryo which gives rise to gastrointestinal and respiratory organs by forming epithelial linings and organs such ...
The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers. Production The ...
On the deep surface of the inner cell mass, a layer of flattened cells, called the endoderm, is differentiated and quickly assumes the form of a small sac, called the yolk sac. Spaces appear between the remaining cells of the mass and, by the enlargement and coalescence of these spaces, a cavity called the amniotic cavity is gradually developed.