Wait cuz i really need the extra braincells

So like y'know how the body can't make extra limbs or shit like that, dont matter gender? then tell me HOW TF WE MAKE CHILDREN???? we cant make A PART of our bodies over again, but AND ENTIRE MAMAL HUMAN CHILD is possible, EVEN MULTIPLE???? like, i kno that the SpErM and the EgG come ToGeThEr TO FORM A cHiLd in the FeMaLe RePrOdUcTiVe sYsTeM but it SOMEWHOW DONT MAKE SENSE. Once ur heart gone, IT GONE, but dont worry, i can make more THROUGH CHILDREN. HOWWWWWWWW THOOOOOOOO?!??!?!?!!