Embryology

The embryology is a scientific discipline which includes the morphological description of the transformations of the egg fertilized into organization ( morphological embryology ) and the study of their determinism ( causal embryology ). L'" embryology causale" is more usually indicated, since the Nineties and the advent of the molecular Génétique, by the term of " biology développementale" who includes also the study of the post-embryonic development.

The Tératologie is the study of the anomalies of the embryo.

History of the embryology

The current model of the development of the embryo rests on the épigénèse which stipulates that this one develops in an increasingly complex way. To it was opposed to the Théorie preformation which sees the embryo as a “miniature” living being where all the bodies are already present.

In 1866 Ernst Haeckel, introduced the Théorie of the recapitulation which does it parallel between the growth of an embryo and the evolution of its species. For example, at a certain stage of their development, the bodies which will form the fins of the embryo of an marine mammal as the Dauphin presents a conformation which points out the legs of the terrestrial animals. This observation coincides with the existence of a terrestrial ancestor. This theory is discussed today.

Embryogenesis of an animal specie standard Chordé E

When the Spermatozoïde fertilizes the Ovule, the development of egg in animal starts.

This development proceeds in five great stages: the segmentation, the gastrulation, organogenesis (with neurulation and metamerisation) and histogenesis.

  1. the segmentation : first phase of the embryonic development characterized by a succession of fast and brought closer divisions, with very short interphases. These divisions, which are in fact of the singular Mitose S, split up egg in a whole of cells Blastomère S.
    La segmentation do not generate the increase in the diameter of the Embryon and are completed at the stage blastula .

  2. the Gastrulation : installation in the embryo of the tridermic Disque embryologic is of the three fundamental layers (Ectoderme, mésoderme and Endoderme which at the man appear as of the 3rd week of development). They derive from the two transitory layers (épiblaste and Hypoblaste) from which will derive the futures Organe S.
  3. the Neurulation : installation of the outlines neurales. The embryo which is the seat is the Neurula. It is a phase characteristic of the Chordé S which corresponds to the rolling up and the welding of the external edges of the gutter neurale. It leads to the formation of the tube neural and the bulb neurale, first outlines of the central Nervous system.
  4. the Métamérisation : fragmentation or budding of the mésoblaste. In the young person neurula thus, the mesodermic blades left and right-hand side extend in a continuous way from one end to another of the embryo. These blades will cut out in a series of successive segments.
  5. : E.g.: at vertebrate the metamerisation generates the celebrities and the Vertèbre S.
  6. the Histogenèse : formation of fabrics by differentiation of the cells embryonnaires.
    Il thus has fabric formation there per transformation of the outlines embryonnaires.
    Les great types of fabrics are: the epithelium S (with glandular fabrics), fabrics muscular, nervous fabrics and conjunctive fabrics.

See too

Simple: Embryology

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