The opening of the cervix is only a few millimeters wide. You'd probably have to block the exit and pump at high pressure to force the stuff in like that.
No, it doesn't have to go through the uterus. At least the semen doesn't... the sperm IN the semen are microscopic and mobile in their own right, capable of 'swimming' several feet. The semen pools around the cervix and the sperm swim OUT of it and into the uterus... that's why a girl can get pregnant from just smearing some semen on the outside of her pussy.
Like Twerp said, to get it to go INTO the uterus would take more pressure than the human penis is capable of generating, and would be horribly painful in all likelyhood.
The cervix is usually filled by a 'plug' of mucous. The sperm can swim through it (think of it as a screening process for the weak/slow sperm), and then they move onwards into the uterus. The semen stays put at the cervix.
http://en.wikipedia.org/wiki/Cervix During orgasm, the cervix convulses and the external os dilates. Dr. R. Robin Baker and Dr. Mark A. Bellis, both at the University of Manchester, first proposed that this behavior worked in such a way as to draw any semen in the vagina into the uterus, increasing the likelihood of conception. Later researchers, most notably Elisabeth A. Lloyd, have questioned the logic of this theory and the quality of the experimental data used to back it.
NOBODY KNOWS FOR SURE WHAT HAPPENS IN THE CERVIX DURING SEX. IT IS A MYSTERY.
Anonymous said: But in this picture, it seems that the semen simply oozes into the uterus by gravity, given the position. What would prevent it from doing that?
