Human Embryonic and Fetal Development : Three-dimensional visualization reconstructed from scanned human data of a 8 cell zygote, a 14-16 day old embryo, a 44 day old embryo, and a 9 week old fetus. The body does not increase greatly in size during the embryonic period. But during the the fetal period, beginning at week nine, a phase of rapid growth starts that continues until after birth.
Prenatal or antenatal development is the process in which a human embryo or fetus (or foetus) gestates during pregnancy, from fertilization until birth. Often, the terms fetal development, foetal development, or embryology are used in a similar sense.
After fertilization, the process of embryogenesis, (the early stages of prenatal development) begins. By the end of the tenth week of gestational age the embryo has acquired its basic form and the next period is that of fetal development where the organs become fully developed. This fetal period is described both topically (by organ) and chronologically (by time) with major occurrences being listed by gestational age.
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