Critical and analytical survey on the periodization of the mammalian prenatal development
1998
Kovachev, K. (Institut po Biologiya i Imunologiya na Razmnozhavaneto i Razvitieto na Organizmite - B"lgarska Akademiya na Naukite, Sofia (Bulgaria))
A critical and analytical survey was performed on the mammalian prenatal development based on a group of distinct criteria: a) relationship between the developing and maternal organisms; b) types of nutrition and protection of the prenatal organism; c) characteristics of the structure - forming processes. In addition to the two periods of the prenatal development which have been introduced in the literature long ago - embryonal and fetal, convincing arguments are presented for the actual existence of an initial period - the zygotic periodd, each of this periods being longer than the previous one. At the same time the stages and steps typical of each period are clearly defined. A number of scientific terms which at present are being erroneously used for descripton of the different periods of the prenatal development, are also more precisely defined.
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