Secrete hormones that influence female and male characteristics, respectively. The function of the testicle is to produce sperm and the male hormone testosterone. Sperm produced in the testicle are transported through thousands of tiny tubes into an adjacent structure called the Epididymis. The epididymis is a rubbery structure attached to the back of the testicle. Sperm is transported out of the epididymis through the vas deference. The vas deference travels up into the groin and dives deep into the pelvis to connect with the urethra.

Diseases
Several diseases can affect the testicle and associated structures. When pain or a mass develops in the testicle or scrotum, one should be evaluated by a physician to rule out infection or, less commonly, a tumor. In patients where pain persists, despite antibiotic therapy, an ultrasound is usually recommended to rule out a tumor. Varicocele is common in young men and usually seen in the left scrotum. It is a dilation of the veins which drain the left testicle.
These veins may cause enlargement of the left scrotum and feel like a bag of worms under the skin.

In most instances, these are of no clinical concern, however, they potentially can cause problems with infertility and pain. In these instances, surgical correction is possible.

Occasionally, fluid will develop around the testicle and this condition is known as a Hydrocele. These are common in newborns and usually spontaneously resolve within the first year of life. In the adult, a hydrocele may develop after trauma or infection. A hydrocele may need to be drained or surgically removed if it causes problems with pain or discomfort.

Torsion of the testicle is a condition where the testicle twists upon itself. When the testicle twists on itself, this will result in blockage of the blood flow to the testicle and ultimately, testicular death. This phenomenon usually is seen in boys up to age 16 years, however, it can also occur in adults. It presents with a sudden onset of excruciating testicular pain. If left untreated for more than twenty–four hours, the testicle is usually permanently damaged. If a patient is seen within a few hours of the onset of pain then the testicle should be surgically untwisted.

Infections in the epididymis are common. This condition is called Epididymitis. Epididymitis may be recurring and cause chronic pain in the scrotum. The usual treatment is with antibiotics, however, a prolonged course may be necessary in select individuals. In severe cases that do not respond to medication, surgery may be necessary to remove nerves going to the testicle or to actually remove the testicle in an effort to relieve pain.

Cysts are very common on the epididymis. On ultrasound evaluation, these can be differentiated from testicular tumors. No treatment is necessary unless there is persistent pain.