Blastopore

As primitive mouth or blastopore, the opening is referred to in embryology at a developing embryo, in which his body surface invaginates the primitive gut.

Most multicellular animals go in the first steps of their embryonic development after formation of the blastula and ( in mammals such as humans ) of the blastocyst through a significant phase gastrulation. This is the germ of a structure with an outer cell layer located, the ectoderm, and an invaginated inner cell layer, the endoderm. Primitive body so obtained has an inner surface to the outer, the indentation represents the primitive gut. The point at which the primitive gut opens to the outside is called the blastopore, because many living things in the mouth develops from this area. Among the two sides built animals ( Bilateria ), it is the Urmünder or protostomes; with them a second opening of the archenteron is formed for excretion in the further development. The protostomes include, for example insects.

In deuterostomes or Neumündern, however, which includes all vertebrates, the primary opening of the blastopore later acts as an excretory opening or anus, and secondarily by breaking opening at the other end of the primitive gut is with them to the ( new ) mouth. In some basal animals such as jellyfish the blastopore both the recording as well as the excretion is later.

The distinction in Urmünder and new mouths at the bilaterians, is an important aspect of the classification of animals, because the similarity of the early stages of development in each case has a common ancestor and thus a relationship of sorts out.

• Organogenesis
• Mouth