Sperm entering Fallopian tubes. Animation of spermatozoa (sperm, the male sex cells) passing through the junction between the uterus and the Fallopian tubes (the uterotubal junctions). If an ovum (egg cell, female sex cell) has been released from an ovary, it will pass down the Fallopian tubes towards the uterus. The sperm that encounter an ovum will attempt to fertilise it as part of the process of sexual reproduction.