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How are sperm made and how long does it take?

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    How are sperm made and how long does it take?

    Sperm have a life-span of up to 5 days in an environment such as the fallopian tubes. In an environment like the vagina or cervix, they only live for a few hours and less than that if exposed to open air. Eggs last for about 24 hours unless they are fertilized.

    The question is what happens to sperm if they are not ejaculated?

    The testes (the part of your testicles that make sperm) send the sperm into a tube called the vas deferens that pass alongside the penis, over the pubic bone, passing the ureters, and connects up to the seminal vesicles. The seminal vesicles send a tube that joins with the urethra in the prostate. During ejaculation, the bladder sphincter is usually closed so that the sperm can only come out.

    In the testes, the spermatids are produced by stem cells inside the seminiferous tubules that are lined with special cells called Sertoli cells. The Sertoli cells are tightly connected to each other, to form a contiguous barrier to protect the sperm cells from antibody, toxins, and other systemic substances that can harm them. In addition, the Sertoli cells are anti-inflammatory.

    In addition, there are nests of cells called the interstitial cells (of Leydig) that make testosterone. The testosterone can diffuse across the Sertoli barrier which is sometimes called the blood-testis barrier. The Sertoli cells themselves secrete a fluid that is relatively rich in potassium, aspartate, and glutamate that sustain and stimulate the development of sperm.

    One important function of the blood-testis barrier is to keep sperm and pieces of sperm from entering the blood stream and inducing an immune response. It would be catastrophic for reproduction if the body were to develop an autoimmune response to its sperm. By the way, I suspect that the cumulus cells of the ovary may have a similar function.

    The testis is constantly making spermatids, at the rate of many thousands a minute. The spermatids are partly motile and head to the Sertoli cells and bury their heads into the cells. The fluid secreted by the Sertoli cells gradually push the spermatids towards the epididymus where proteins are added to their surface and the spermatids begin their transformation to sperm.

    The epididymus is a coil of tubes that may exceed 6 meters (18 feet). By the time the sperm leave the epididymus, they are fully capable of motility and fertilization. At this time there are about 50 million spermatid per ml of fluid. By the time they leave the epididymus, there may be 5000 million or 5 billion sperms per ml. The seminal vesicles produce additional fluid that dilute the ejaculate to about 100 million sperm per ml. Each ejaculate may contain as much as 300 million sperm.

    It takes 74 days from the time spermatids are made to the time when they enter the epididymus. It takes 20 days for the sperm to traverse the epididymus and complete their metamorphosis. They are stored for at least six days in the vas deferens before they enter the seminal vesicles and can be ejaculated. Altogether, the process takes about 100 days.

    Last edited by Wise Young; 12 Jan 2008, 4:17 AM.

    interesting info. seems nobody has anything to say. i thought i could help out , sorry Dr. Young
    oh well



      I was thinking about the situation the other night and realized that I did not know how long sperms took to develop. So, I thought that I would look it up and the answer turned out to be 100 days...

      It is quite amazing that this elaborate system was developed and is our lifeline to continued survival. If this process were to fail, our species would not be able to reproduce. From the spermatogonia, the Sertoli cells, to the vas deferens, the seminal vesicles, prostate, and urethra... these are all designed to make, store, and deliver the packages of genes that make us what we are.

      The reason why I was thinking about this is because there has long been a myth that people with spinal cord injury are less fertile. This was attributed to the fact that men with spinal cord injury sat a lot and this resulted in increased temperature of the testicle.

      So, I began to wonder how long the sperm actually reside in the testicles before they are used. Well, it is a fairly long time: 100 days. However, I am not convinced that men with spinal cord injury have impaired sperm as much as they don't have the optimal semen. In any case, that is another story.



        Very intresting, Thanks Wise



          Interesting subject...thanks for the information, Dr. Young...