The ectoderm

The ectoderm is outside embryonic leaf, which in the early fetal period is developing skin epithelium, or the epidermis, and nervous system. The part of external embryonic piece that goes into the construction of skin cancer, skin called the ectoderm, and the part that form the nervous system,- neuroectodermal.

The ectoderm (from the Greek. ektos - out and derma - skin layer) - outer embryonic leaf, most of the external layers of the cells of the embryo in all multicellular animals. The ectoderm first consists of one closed homogeneous layer of undifferentiated cells, which in the course of further differentiation are divided into different from each group is different ectodermal beginnings. The cells of each of them specializing in different directions, give rise to specific tissues.
The germ of higher vertebrates and human rights in the course of gastrulation first are the primary ectoderm (epiblast) and endoderm. Only after separation from epiblast material medium embryonic leaf, or mesoderm (see), the outer leaf of the embryo becomes the actual ectoderm (secondary), which is differentiated to skin the ectoderm, nazaralieva the ectoderm and neuroectoderm.
Skin ectoderm forms a further skin epithelium, or the epidermis, with its tissue derived (skin cancer, hair, nails, etc.,) and the epithelium of the vestibule of the oral cavity and anal Department of the rectum. The epithelium of the most part of the mouth, pharynx, oesophagus and respiratory tract, also related to the epithelium of the skin type, arises from the special germ - prechordal plate.
From nazaralieva the ectoderm are formed covering epithelium yolk SAC (fish), serous membranes of the embryo (reptiles, birds) and the epithelium lining the cavity of the amnion (all higher vertebrates). Trophoblast embryos of mammals and humans, too, is boobless during crushing eggs and early specializing part nazaralieva the ectoderm.
Neuroectoderm (a rudiment of the nervous system) presents neural plate, ganglion the plate and placode. Neural plate representing the medial area of the ectoderm on dorsal side of the embryo occurs under the influence of spreading it in the course of gastrulation material chordamesoderm. She is bending, forming neural groove, which is then bound up edges, turns into a nervous tube - a root of the spinal cord and brain. Last sank beneath the skin the ectoderm, over which it is linked. Nervous rollers - thick edges nervous groove - after its closure in the receiver are in the form of a ganglion of the plate, or neural crest (between neural tube and skin ectoderm). Ganglion record, segmenters, forming the beginnings of sensitive cerebrospinal node. Individual cells migrating far on the periphery, form the beginnings of sympathetic ganglia and brain substance napochechnikov or differentiate into the pigment cells - melanophores. In the field of head and neck part of the ganglion cells of the plate gives rise to ectomesenchyme (see Mesenchyma). Placode - small Islands of neuroectoderm in the structure of the skin ectoderm - are the beginnings of a number of cranial nerve nodes, membranous labyrinth of the inner ear and eye lens.
The epithelium and cancer, developing from skin and nazaralieva the ectoderm and prikordonniy records, based on all properties related to epidermal tissue type. Tissue derived neuroectoderm (neurons, neuroglia, pericrocotus cells epithelium ependymal group) are phonevalley tissue type. Cm. also Embryonic leaves.