In the mans body, the pituitary gland in the brain sends a hormone, called follicle-stimulating hormone, (FSH) to the testicles, which are the male sex glands. FSH signals the testicles to produce sperm, which are the male reproductive cells. Sperm are so small they can only be seen through a microscope. Each tiny sperm has a tale that allows it to move. After sperm are produced in the testicles, they travel through a tube called the vas deferens to the seminal vesicle, which holds the mature sperm. A gland called the prostate makes seminal fluid, which is the fluid that will transport the sperm in the urethra. The urethra is a tube that extends from the bladder, through the prostate, then through the penis to the outside of the mans body. During sexual activity, the prostate gland becomes as full of fluid as it can comfortably hold, and it contracts (squeezes). As the prostate contracts, it draws sperm from the seminal vesicle. Seminal fluid mixed with sperm is called semen. The contractions of the prostate gland force the semen through the urethra and out the tip of the penis. This is called ejaculation. The ejaculate (semen) is a teaspoon to a tablespoon of thick milky liquid and contains millions of microscopic sperm. During sexual activity, but before ejaculation, the penis becomes engorged with blood. This causes the penis to become firm and erect, and is called the male erection. The male erection allows the penis to pass into the vagina of the woman. When a man has an erection a valve closes between the prostate gland and the bladder to prevent urine from being released when semen is ejaculated. Practically speaking, this means that a man cannot urinate and ejaculate at the same time. To begin the reproductive cycle in a womans body, a hormone, called follicle-stimulating hormone, (FSH) is produced by the pituitary gland in the brain. FSH travels through the bloodstream to the ovaries, causing a few of the many tiny follicles there to begin ripening, or maturing. Each follicle is a tiny ring of cells with a tiny ovum, or egg, inside. As the follicles ripen, they produce another hormone, called estrogen. Estrogen causes the cervix, the opening of the uterus, to begin making moisture and mucus. This is when a woman notices wetness or mucus outside the vagina. This mucus is not a sign of disease. It is a natural part of the cycle and indicates that the ova are maturing in the ovaries. If intercourse occurs at this time, the mucus will protect the sperm from the acidity of the vagina, assuring that the sperm will still be alive at ovulation. Estrogen also causes the endometrium, the lining of the uterus, to grow soft and spongy, forming a kind of bed that can, in the event of pregnancy, hold and nourish a baby. Finally, estrogen signals the pituitary gland in the brain that some follicles have matured in the ovaries. When the pituitary gland receives the message that some follicles have matured, it produces another hormone, leutenizing hormone, or LH. LH causes one of the ripening follicles to release its ovum into a fallopian tube. This is called ovulation. Once ejaculation has deposited the sperm in the womens vagina, they swim up the vagina to the uterus. They do not know which fallopian tube may contain the ovum, and so they swim both ways. When a sperm penetrates the ovum, it is called fertilization. Dividing and maturing as it goes, the fertilized ovum is moved slowly along the fallopian tube toward the uterus by the cilia, tiny hairs inside the fallopian tubes. In six or seven days, the fertilized ovum implants in the endometrium (the lining of the uterus), which is the bed that has been created to receive it. Menstruation does not occur, because the fertilized ovum, growing and developing in the uterus, creates hormones that maintain the uterine lining. The woman realizes she has conceived |
