ABSTRACT
Embryonic life commences with fertilization, which is the progression of events that begins when a spermatozoon makes contact with an oocyte or its investments, and ends with the intermingling of maternal and paternal chromo somes at metaphase of the first mitotic division of the zygote. Successful initiation of fertilization requires that the ovum descending in the uterine tube meet the ascending viable sperm at the right time, in the right place and under the right circumstances (Fig. 3.1).
