Sperm Production
The Male Reproductive System
Sperm are produced the in male reproductive system. The male reproductive system includes the testes, urethra, vas deferens, prostate gland, seminal vesicle, and penis.
Drawing of the Male Reproductive system. Image courtesy of https://commons.wikimedia.org/wiki/Image:Male_anatomy.png under the the terms of the GNU Free Documentation License
Testes and Scrotrum
The testes are a pair of oval, slightly flattened bodies measuring about 4cm in length and 2.5cm in diameter. Together with the epididymis, they lie in the scrotrum below the penis. The walls of the cavity of in which the testes and the epididymis reside are known as tunica vaginalis. The testes have two distinct functions, spermatogenesis and androgen production. The testes contain coiled structures called seminiferous tubules, which are the sites of sperm production.
Epididymis
The epididymis lies on top of the seminiferous tubules. Immature sperm migrate from the seminiferous tubules to the epididymis where they are stored and allowed to mature It is formed from an irregular twisted tube called the duct of the epididymis. The epididymal duct is about 600cm long and ends as the tail of the epididymis, then becomes the vas deferens.
Vas (ductus) deferens and Seminal vesicles
The vas deferens is a direct continuation of the epididymis. It is a 45cm long structure that begins at the lower end of the epididymis and ascends towards the posterior aspects of the testes. The vas deferens crosses over the ureter to meet the duct of the seminal vesicle. Together, the vas deferens and the duct from the seminal vesicle form the ejaculatory duct.
Ejaculatory Duct
The ejaculatory duct is a short duct, about 2.5cm.In the ejaculatory ducts, a liquid secretion from the seminal vesicles mixes with the sperm. Seminal fluid contains fructose sugar, which the sperm use as fuel as well as alkalines, which help to counteract the naturally acidic environment of the vagina and uterus providing the sperm a better chance for survival. The liquid mixture is propelled forward through the ejaculatory ducts toward the urethra. When liquid mixture passes through the prostate gland, milky prostatic fluid is added, forming the substance called semen. The prostatic fluid helps the sperm swim faster, which is important for getting to the correct site of fertilization and fertilize the oocyte.
Erection, Ejaculation and Emission
Before intercourse, the penis fills with blood and becomes erect. With sufficient stimulation, the ejaculatory process begins. The mature sperm travel from the epididymis through the vas deferens. The vas deferens 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 pass into the ejaculatory ducts. Finally the seamen is ejaculated through the far end of the urethra at the end of the penis.
Click here to view animation of sperm production (Opens new window).