Male genitalia refers to the reproductive organs that produce sperm, deliver it during intercourse, and secrete testosterone. These structures include both external parts you can see (the penis and scrotum) and internal organs (the testes, epididymis, vas deferens, and prostate gland). Together, they serve two core biological functions: reproduction and hormone production.
External Structures
The two visible parts of male genitalia are the penis and the scrotum. The penis contains spongy tissue that fills with blood during arousal, causing an erection. It also houses the urethra, a tube that serves double duty as the exit route for both urine and semen, though never at the same time. Muscles at the base of the bladder close off urine flow during ejaculation.
The scrotum is the pouch of skin that hangs below the penis and holds the testicles. It might look simple, but it plays a critical role in temperature control. Sperm production requires a temperature slightly below core body heat, so the scrotum constantly adjusts. Muscles in the scrotal wall pull the testicles closer to the body when it’s cold and let them hang lower when it’s warm, increasing the exposed surface area to release excess heat.
Internal Organs and What They Do
The testicles (also called testes) sit inside the scrotum and are roughly the size of two large olives. They are the primary production centers for both sperm and testosterone. Most people have two, one on each side.
Once sperm cells are made, they move into the epididymis, a tightly coiled tube resting along the back of each testicle. Sperm that leave the testicle are actually immature and unable to fertilize an egg. The epididymis stores them while they finish developing. During arousal, muscle contractions push the now-mature sperm forward into the next structure: the vas deferens.
The vas deferens is a long, muscular tube that carries sperm from the epididymis up into the pelvic cavity, looping behind the bladder. From there, sperm travel to the urethra in preparation for ejaculation. This is the tube that gets cut during a vasectomy.
The prostate gland, about the size of a walnut, sits just below the bladder with the urethra running through its center. It adds nutrient-rich fluid to the ejaculate that helps keep sperm alive. The seminal vesicles, two small glands behind the bladder, contribute about 60 percent of the total fluid volume in semen, with the prostate supplying most of the rest. The sperm cells themselves make up only a small fraction of the overall volume.
How Testosterone Shapes Development
Testosterone is the primary hormone behind the development and maintenance of male reproductive anatomy. Its influence starts before birth. During fetal development, testosterone drives the formation of the internal reproductive tract, while a more potent form of the hormone triggers the development of the prostate, scrotum, and penis. Around the seventh month of pregnancy, rising testosterone levels cause the testes to descend from the abdomen into the scrotum through the inguinal canal.
If a baby is born with undescended testes that haven’t moved into position by four to six months of age, hormone treatment can sometimes help complete the process.
Testosterone’s role picks back up during puberty. The first visible sign of male puberty is testicular growth, typically when the testes reach about 2.5 centimeters in length. From there, development progresses through recognizable stages. The penis and scrotum enlarge and darken in color. A major growth spurt in height tends to happen mid-puberty, and sperm production typically begins in the later stages, usually after the testes have reached 4 to 4.5 centimeters. By the end of puberty, adult testicular volume exceeds 20 milliliters.
Sperm Production Is Continuous
Unlike the female reproductive system, which releases one egg per cycle, the testes produce sperm continuously from puberty onward. The full process of creating a mature sperm cell takes roughly two to three months in humans, moving through multiple stages of cell division and development within the testicle before the sperm enter the epididymis for final maturation. Production does gradually decline with age but never fully stops in most healthy individuals.
Common Health Issues
One of the more common conditions affecting male genitalia is varicocele, an enlargement of veins within the scrotum similar to varicose veins in the legs. Varicoceles are present in about 40 percent of men who experience infertility, likely because the pooled blood raises scrotal temperature enough to impair sperm production. Many varicoceles cause no symptoms and need no treatment, but surgical repair is an option when fertility is a concern.
Other conditions that can affect these structures include inguinal hernias (where tissue pushes through a weak spot in the abdominal wall near the groin), infections of the epididymis or prostate, and testicular torsion, where the spermatic cord twists and cuts off blood supply to the testicle. Torsion is a medical emergency that requires immediate treatment to save the testicle. Routine self-exams of the testicles can help catch unusual lumps or swelling early, which is particularly relevant for detecting testicular cancer, one of the most common cancers in younger men.