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A woman's eggs choose lucky sperm during last moments of conception, study finds
Sperm wars illuminated | Nature
Suarez, A. At coitus, human sperm are deposited into the anterior vagina, where, to avoid vaginal acid and immune responses, they quickly contact cervical mucus and enter the cervix. Cervical mucus filters out sperm with poor morphology and motility and as such only a minority of ejaculated sperm actually enter the cervix. In the uterus, muscular contractions may enhance passage of sperm through the uterine cavity. A few thousand sperm swim through the uterotubal junctions to reach the Fallopian tubes uterine tubes, oviducts where sperm are stored in a reservoir, or at least maintained in a fertile state, by interacting with endosalpingeal oviductal epithelium. As the time of ovulation approaches, sperm become capacitated and hyperactivated, which enables them to proceed towards the tubal ampulla. Sperm may be guided to the oocyte by a combination of thermotaxis and chemotaxis.
Sperm wars illuminated
Every time a man ejaculates about 55m sperm are released. This is equivalent to more than six times the entire population of London or New York, and more than twice the population of Shanghai city. But of course, not all of these sperm will go on to become babies. In fact only around 15 sperm are able to make it through the female reproductive tract. This is because for a sperm, the journey to fertilise an egg is a treacherous one.