The Great Sperm Race
This documentary retraces the journey of conception scaled up to human size, from the sperm production to the fertilization of the egg. There are over 250 million human sperm cells in the testicles waiting for the muscle contractions to expel them through the urethra (ejaculation), but only a few thousands will enter the fallopian tubes, and only one will get to fertilize the egg in the woman’s body. In the documentary, Dr. Allan Pacey compares the excursion of sperm as a war, because they have to go through lots of obstacles in the female reproductive system, like the acidity of the vagina, the mucus of the cervix, the narrowness of the entrance of the cervix, and the white blood cells of the immune system. While the sperm try to find a way through the uterus, over 99% of them would be dead or dying. We learn from the documentary that X and Y sperm are produced in almost equal number. However, there is a difference in their motility. X sperm tend to be faster, but Y sperm live longer. Once created, each sperm ends up in a structure on top of the testicle, called the epididymis. This is where over a billion sperm mature and most wait. When ejaculation occurs, the sperm go from the epididymis to the vas deferens, which is a sperm duct extending from the scrotum through the inguinal canal and into the pelvic cavity. After they have made their way through these ducts, the sperm are being released into the ejaculatory ducts, which pass through the prostate gland and leads to the urethra. Finally, the sperm is being conducted through the penis to the outside of the male body. After the sperm have entered the vagina, their objective is to reach a tight opening high above the vagina: the cervix. The cervix constitutes a physical obstacle because of its mucus, called the cervical mucus. It is like a barrier for the sperm, because it selects only sperm with normal motility. Only 20% maximum of these sperm have an appropriate size and shape and will...
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