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Preimplantation Period
This takes place during the first week after conception, during conception a woman's ovum is penetrated by a mans sperm during fertilization. This union of ovum and sperm subsequently form a fertilized egg or zygote. -
Mitosis
After fertilization, the zygote then undergoes mitosis, or individual cell division, that splits into more and more cells due to cleavage. Because of the on going process of mitosis and secretion of fluid by the cells within the morula, the zygote now becomes a Blastocyst. Blastocyst splits into smaller and more numerous cells as it undergoes successive cell division. -
Implantation
By the end of the first week, the blastocyst stops traveling and undergoes implantation an thus becomes embedded in the prepared endometrium, the inner most lining of the uterus on its back wall. After a week of cleavage, the blastocyst consist of a layer of peripheral cells, the Trophoblast Layer, and a small inner mass of embryonic cells, or Embryoblast Layer -
Embryonic Period
The second period of prenatal development, the Embryonic period, extends from the beginning of the second week to the end of the eight week. Certain physiological processes or partial and temporal events called pattering occur during this period for example: Induction, Proliferation, Differentiation, Morphogenesis, Maturation. -
Induction
This is the first physiological process involved during prenatal development. This is an action of one group of cells on another that leads to the establishment of the developmental pathway in the responding tissue. -
Proliferation
This follows Induction, proliferation which controls cellular growth present during prenatal development, later migration of these proliferated cells also occur. Finally growth also occurs as a result of an accumulation of cellular byproducts. -
Differentiation
In the process of differentiation, a change occurs in the embryonic cells, which are identical generically but later become quite distinct structurally and functionally. These functions are minimal at this time, the beginning of major tissue types, organ systems are formed during this period from these specialized cells. -
Morphogenesis
Is the the process of development of specific tissue structure and shape. Morphogenesis occurs due to migration of proliferation of embryonic cells, which is followed by the induction of those cells. -
maturation
Finally, the physiologic process of maturation of the tissue types and organs begins during the embryonic period and continues later during fetal period. Thus maturation is not the attainment of just the correct adult size but also the correct structure and function of tissue types and organs.
