i don't know too much biology, but i don't believe a penis should go passed the gate to the baby chamber or whatever it is called
there are BRUTAL methods to pass the cervix and enter the uterus, but......it is not a good thing to do. Sex is typically exaggerated in art and has been done in Japan, especially in the Shunga period of art where men would be painted having penises thicker than their leg even though.....well..... Anyway the amount of semen is usually milliliters at best which is never directly injected into the uterus. The strongest sperm has to swim on their own, from the cervix to the uterus and locate the egg and have enough strength left to penetrate the egg cell membrane. In this picture it look to be gallons with overflow to spare.