Let me tell you ‘bout the “Birds and the Bees”
And the flowers and the trees
And the moon up above
And a thing called “Love” (Herb Newman)
On the day of fertilization, still within the comforting confines of the fallopian tube’s ampullary region, the genetic material of the sperm (male pronucleus) and the genetic material of the egg (female pronucleus) fuse to form an early embryo called a 2PN for two pronuclei. By the second day following fertilization the embryo develops into a two to four cell embryo and continues its journey down the fallopian tube into what is called the isthmic region. These embryonic cells continue to divide producing a ball or cluster of cells by the fifth day after fertilization called a blastocyst. At this blastocyst stage of development the embryo leaves the fallopian tube and enters into the uterine cavity via the tubal ostia. Once in the uterine cavity the blastocyst literally hatches from its zona-like shell. After an additional two days of wandering, seeking a safe and secure place to land, the hatched blastocyst finally burrows into the luxurious uterine wall from which, if all goes right, a baby is born nine months later.