Sperm journey for fertilization

Mammalian fertilization comprises sperm migration through the female reproductive tract, biochemical and morphological changes to sperm, and sperm-egg interaction in the oviduct. Recent gene knockout approaches in mice have revealed that many factors previously considered important for fertilization are largely dispensable, or if they are essential, they have an unexpected function. This Review focuses on the advantages of studying fertilization using gene-manipulated animals and highlights an emerging molecular mechanism of mammalian fertilization. In the early s, Min Chueh Chang and Colin Russell Austin independently found that mammalian sperm must spend some time in the female reproductive tract before they acquire the ability to fertilize eggs 1 , 2. This simplified in vitro experimental system 5 also allowed researchers to intensively study the mechanism of fertilization. Indeed, using this system together with biochemical approaches, such as competitive binding of antibodies and ligands that interact with sperm, eggs, and their surroundings, various factors were reported to be important for mammalian fertilization.

While you release only a single egg each month, your partner releases millions of sperm in a single ejaculation — all with their eye on that single prize. But only one of those sperm will be crowned the victor, and the odds are stacked against fertilization. Luckily, egg and sperm have developed some pretty nifty tricks to give themselves a fighting chance. Fortify the troops.

Fig 1. The journey begins with millions of sperm cells that are released into the female reproductive tract during intercourse. The sperm cells gain their full ability to swim when they are ejaculated into the reproductive tract [ 1 ],[ 2 ]. Upon ejaculation, the sperm cells are enclosed in a fluid called seminal plasma or semen, which is a mix of fluids from the testes, seminal vesicles, prostate, and the bulbourethral glands. The fluid contains elements which protect the sperm cells during their journey towards the egg.

Achieving a healthy pregnancy is a complicated, multi-stage process involving two people. Every month, the female ovulates one mature egg from one of her ovaries. Here, it will begin to move slowly down the tube towards the womb uterus.