Epididymis
Each epididymis is a tightly coiled, thread-like tube that is approximately 6 meters long. This tube is connected to the ducts within the testis. The epididymis covers the top of the testis, runs down the testis' posterior surface, and then courses upward to form the vas deferens.

The epididymis secretes the hormone glycogen, which helps sustain the lives of stored sperm cells and promotes their maturation. When immature sperm cells enter the epididymis, they are not mobile. However, as the sperm cells travel through the epididymis, they mature and become mobile. Once the sperm cells are mature, they leave the epididymis and enter the vas deferens.

Vas Deferens
The vas deferens is a small tube that connects the epididymis and ejaculatory duct. It ascends as part of the spermatic cord through the inguinal canal of the lower abdominal wall into the pelvic cavity, and transmits the sperm to the ejaculatory ducts.

Ejaculatory Ducts
The vas deferens and the seminal vesicles converge, just before the entrance of the prostate gland, to form the ejaculatory ducts (fig. 1-60). The ejaculatory ducts open into the prostatic urethra. Its function is to convey sperm cells to the urethra.

Seminal Vesicles
The seminal vesicles are two pouches that are attached to the vas deferens near the base of the urinary bladder. The lining of the inner walls of the seminal vesicles secrete a slightly alkaline fluid. This fluid is thought to help regulate the pH of the tubular contents as sperm cells are conveyed to the outside. The secretion produced by the seminal vesicles also contains a variety of nutrients, such as fructose (simple sugar), that provides the sperm cells an energy source.

At the time of ejaculation, the contents of the seminal vesicles are emptied into the ejaculatory ducts. This action greatly increases the volume of fluid that is discharged by the vas deferens.

Urethra
The urethra is an important organ of both the urinary and reproductive systems. The role of the urethra, in the reproductive system, is to transport sperm through the penis to outside the body. See "The Urinary System" section for information on the structure of the urethra.

Prostate Gland
The prostate gland, made of smooth muscle and glandular tissue, surrounds the first part of the urethra. It resembles a chestnut in shape and size, and secretes an alkaline fluid to keep the sperm mobile, protecting it from the acid secretions of the female vagina. This substance is discharged into the urethra as part of the ejaculate, or semen, during the sexual act.

Bulbourethral Glands
Bulbourethral glands, also known as Cowper's glands, are two pea-sized bodies located below the prostate gland and lateral to the membranous urethra. These glands are enclosed by fibers of the external urethral sphincter. They release a mucous-like fluid in response to sexual stimulation and provide lubrication to the end of the penis in preparation for sexual intercourse.

Semen
Semen is composed of sperm and secretions from the seminal vesicles, prostate, and bulbourethral glands. It is discharged as the ejaculate during sexual intercourse. There are millions of sperm cells in the semen of each ejaculation, but only one is needed to fertilize the ovum. It is generally considered that fertilization of the ovum occurs while it is still in the fallopian tubes. Therefore, it is apparent that sperm cells can move actively in the seminal fluid deposited in the vagina and through the layers of the secretion lining the uterus and fallopian tubes.