I.

Introduction

Testis, also called testicle, one of a pair of male sex glands that produce sperm cells. Testes are present in most animals. In backboned animals the testes produce male sex hormones, called androgens, as well as sperm.

In man the testis is an oval organ about 5 cm (about 2 in) long. During embryonic development it is located in the abdominal cavity, but about a month before birth it normally descends into a pouch of skin called the scrotum. Each testis contains about 800 narrow twisting tubes, called seminiferous tubules, that are lined with cells that, upon maturation, divide to form the sperm. The seminiferous tubules merge and form a larger tube, the epididymis. Sperm travels from the testis through the epididymis to the vas deferens, which carries the sperm to the urethra. Sperm exits from the urethra during ejaculation (the release of semen during orgasm). In man the sex hormone produced by the testis is testosterone, which controls the growth of the male reproductive system and stimulates the development of the male secondary sexual characteristics, such as the growth of the beard, the deepening of the voice, and the male contours of the body. It also influences male sexual behavior (see Human Sexuality).

II.

Disorders of the Testis

Occasionally—in 2 percent of full term and 10 percent of premature male babies—one or, more rarely, both testes will fail to descend from the abdomen into the scrotum during embryonic development. Often the affected testis will descend on its own within a few months of birth. Undescended testis is sometimes caused by dysfunctional hormones that control the development of the spermatic cord, which is comprised of the vas deferens and supporting nerves and blood vessels. When the hormones do not send the correct signals, the spermatic cord does not lengthen sufficiently for the testis to descend, develop normally, and eventually produce sperm. If neither testis descends, the man will be infertile. The problem may be corrected by surgery within the first few years of life.

A direct blow to the scrotum or twisting of the testis and spermatic cord may cause painful swelling. If pain is accompanied by fever, the swelling may be caused by infection of the testis or epididymis. Swelling without pain may indicate excess fluid or sperm in the epididymis, the presence of varicose veins in the scrotum, or collected blood in the scrotum as a result of injury. Less frequently, painless swelling may be one of the first signs of testicular cancer.

III.

Testicular Cancer

Testicular cancer is one of the most common cancers affecting men between the ages of 15 and 34, although it can occur in men outside this age range as well. It is more common among men who had an undescended testis that was not corrected in early childhood. A successful cure is almost always possible if the cancer is detected early, allowing a 95 percent survival rate when the cancer is detected early. The survival rate drops to 75 percent if the cancer spreads before being detected.

Testicular cancer is often detected by the man himself as a firm, usually painless lump in the testis. A physician conducts a complete medical exam and history, along with blood and urine tests and chest X rays to exclude other causes. If these are ruled out, a biopsy (removal and microscopic examination of cell tissue) is performed on testicular tissue to confirm a diagnosis of cancer. The testicle must then be removed through the groin (a surgical process called orchiectomy). Additional treatment may involve radiation therapy on the remaining testis and lymph glands, or chemotherapy, or a combination of both.

Because early detection is so important in achieving a successful cure, men should perform testicular self-examination once a month, looking for unusual changes in the appearance and feel of the scrotum.