Sperm Production: Intermediate
Ebix Inc.
Key male reproductive organs include the testes, urethra, vas deferens, prostate gland, seminal vesicles, and penis. The testes contain coiled structures called seminiferous tubules, which are the sites of sperm production. A woman’s ovaries usually produce only one egg per month, while a man’s seminiferous tubules produce more than 12 billion sperm per month. On top of the seminiferous tubules is the epididymis. The immature sperm migrate there to mature, and after maturing they are stored there. The migration of the sperm from the seminiferous tubules to the epididymis usually takes about 20 days. Before intercourse, the penis fills with blood and becomes erect. With sufficient stimulation, an ejaculatory process begins. Mature sperm travel from the epididymis through the vas deferens, which is a narrow, muscular tube about 18 inches long. Its smooth muscle contractions propel the sperm forward. They arrive first at the ampulla, the widest part of the vas deferens, and then they pass into the ejaculatory ducts. Next, a liquid secretion from the seminal vesicles mixes with the sperm. This secretion contains fructose (a sugar), which sperm use as fuel. It also contains alkalines, which help to counteract the naturally acidic environment of the woman’s vagina and uterus. The secretions are propelled forward through the ejaculatory ducts toward the urethra, passing first through the prostate gland, where milky prostatic fluid is added, forming the substance called semen. Finally about a teaspoon of semen is ejected, or ejaculated, through the end of the urethra at the end of the penis. From the time the sperm leave the male body, they have between 12 and 48 hours to find and fertilize an egg cell. Most of the sperm will not make it. Of approximately 300 million sperm in one ejaculation, only about 200 will survive to reach the egg cell; only one of those might succeed in fertilizing it.