Resumo
At mating or artificial insemination, sperm begin their movement towards the site of fertilization. However, most sperm are lost due to retrograde flow and very few ultimately reach the upper oviduct where fertilization occurs. The complex structure of the oviduct functions to store sperm, to increase their lifespan, and to release and move sperm towards the oocytes in the ampulla. To accomplish this feat, the oviduct has complex folds that provide direction to sperm, waves of fluid that carry sperm and also provide sperm direction, adhesive glycans that retain sperm in the isthmus, and a signaling sperm to promote sperm release from the isthmus for fertilization. A better understanding of how the oviduct accomplishes these goals will likely lead to improved sperm storage and release and enhanced fertility.