The sperm goes through a lot just to be fertilized so let go with sperm and see how it fertilized.
uterus
it's not just one sperm it's many and then only one makes it to the end. they go through acid that protects the pathogen
fallopian tube
the vagina doesn't kill all the sperm but here in the cervix most of them get stuck or lost in one of very many pathogens
implantation in the uterus
there is yet still more sperm and isn't just a few but the cervix killed many. here in the uterus, the sperm is attacked by white blood cells. and then the sperm searches for the fallopian tube.
now i just need to find the tubes
here in the fallopian tubes, they is very few sperm left and they just have to survive if they are healthy
where did everyone else go we hand so many and now they are all gone
now they must find an egg at the upper end and grow