The Journey of a Sperm Cell
The male gametes, called sperm cells, are produced over roughly a seventy day period in the testes. The testes are filled with seminiferous tubules lined with sperm nurse cells, through which the gametes are able to move during their production. Surrounding the tubules lie Leydig cells responsible for producing testosterone, which in turn regulate sperm production. Such hormones also stimulate sperm production indirectly, by acting upon the nurse cells. As sperm production is a constant process, these sex cells can be found at varying stages of development within the testes at any time.
After sperm has been produced in the testes, it travels up through the sperm duct whilst mixing with fluids produced by the glands – these fluids provide the sperm with nutrients. This mixture of sperm and liquid is known as semen. Eventually the sperm will reach the urethra from the ejaculatory duct, where it is carried to the penis. The urethra is a tube located inside the penis that can carry urine or semen – adapted with a ring of muscle to ensure the two liquids do not mix. A valve at the base of the urethra directs the flow of either urine or semen out of the urethral meatus.
The penis has two main functions – to pass urine out of a male’s body and to pass semen into the vagina of female during sexual intercourse. The vagina is a muscular tube leading from the cervix to the outside of the body. The opening of the vagina has folds of skin called labia that meet to form a vulva (this is where the urethra opens up to). Once the sperm has entered the female within the semen, it swims up through the cervix into the uterus. The cervix is a ring of muscle at the lower end on the uterus, which keeps the baby in place whilst a woman is pregnant. The uterus, also known as a womb, is essentially a muscular bag with soft lining – the site where the baby develops until birth.
Each ovary is connected to the uterus via a tube – the Fallopian tube. This...