The scrotum and testicles are not the same thing. The scrotum is the pouch of skin and muscle that hangs below the penis, while the testicles are the two egg-shaped organs inside that pouch. Think of it like a bag and its contents: the scrotum is the bag, and the testicles are what it carries.
What the Scrotum Actually Is
The scrotum is a thin sac made of skin and smooth muscle. It divides into two compartments, one for each testicle. Besides the testicles themselves, the scrotum holds several other structures: the epididymis (a coiled tube where sperm mature after being produced), the spermatic cord (which contains blood vessels and the tube that carries sperm upward), and layers of protective tissue.
The scrotum’s main job is protecting the testicles and keeping them at the right temperature. Sperm production requires a temperature about 2 to 8°C (roughly 4 to 14°F) below normal body temperature. The scrotum manages this through a built-in cooling system. A layer of smooth muscle in the scrotal wall, called the dartos, and another muscle called the cremaster work together to pull the testicles closer to the body when it’s cold and let them hang lower when it’s warm. A network of arteries and veins around the testicles also acts as a heat exchanger, cooling incoming blood before it reaches the organs.
What the Testicles Do
The testicles are the reproductive glands themselves. They have two critical functions: producing sperm and producing testosterone. These jobs happen in different parts of the testicle. Sperm are made inside tightly coiled tubes called seminiferous tubules, while testosterone is produced by specialized cells in the tissue surrounding those tubules. These cells respond to hormonal signals from the brain, converting cholesterol into testosterone through a chain of chemical steps.
Testosterone does far more than drive reproduction. During fetal development, it’s responsible for the formation of male genitalia and influences brain development. Throughout life, it affects muscle mass, bone density, body hair, and sex drive. The testicles are the body’s primary source of this hormone.
Why the Difference Matters for Pain
The scrotum and the testicles have different nerve supplies, which is why problems in one can feel different from problems in the other. The scrotal skin gets its sensation from several nerves, and the specific nerve involved depends on which part of the scrotum is affected. The front surface, the sides, and the back are each served by different nerve branches originating from the lower spine and sacral region.
This means a skin irritation on the scrotum (like an ingrown hair or rash) feels distinctly different from a deep ache inside a testicle. Scrotal skin pain tends to feel sharp and localized, similar to skin pain elsewhere on the body. Testicular pain often feels like a dull, heavy ache that can radiate into the lower abdomen or groin, because the nerves serving the testicles connect to spinal segments that also receive signals from those areas.
Conditions That Affect One but Not the Other
Medical problems can target the scrotum, the testicles, or structures between them, and telling these apart matters for getting the right treatment.
- Scrotal conditions include skin infections, cysts in the scrotal wall, and hydroceles (fluid buildup within the scrotal sac that surrounds a testicle). These involve the pouch itself or the space around the organs, not the organs directly.
- Testicular conditions include orchitis (inflammation of the testicle, often from a viral infection), testicular torsion (where the testicle twists on its cord, cutting off blood supply), and testicular cancer. These originate within the organ itself.
- Epididymal conditions like epididymitis (infection or inflammation of the epididymis) affect a structure that sits inside the scrotum but outside the testicle. Bacterial infections are a common cause and are typically treated with antibiotics.
How to Tell Them Apart by Touch
During a self-exam, you can feel the difference between these structures clearly. Standing in front of a mirror, hold each testicle between your fingers and thumbs, with your index and middle fingers underneath and thumbs on top. The testicle itself feels smooth and firm, like a hard-boiled egg. At the top and back of each testicle, you’ll feel a softer, rope-like structure. That’s the epididymis, a normal part of the anatomy that sometimes gets mistaken for an abnormal lump.
The scrotal skin is the wrinkled outer layer you see. Bumps on the skin surface, like ingrown hairs or small cysts, are scrotal issues and not signs of testicular cancer. What you’re checking for during a self-exam is a hard lump or swelling on the testicle itself, which feels different from the soft epididymis and distinctly different from anything on the skin surface. Knowing these structures are separate makes it much easier to notice when something has changed.