scrotum
Meaning of scrotum: An organ deliberately kept outside the body, because the cells it protects cannot do their work at core temperature.
Definition of scrotum
The scrotum is the pouch of skin and muscle hanging behind the penis that holds the testicles. Sitting outside the body cavity keeps its contents a few degrees below core temperature, which normal sperm production requires. A thin muscle layer in its wall contracts and relaxes, drawing the testicles closer to the body or letting them hang lower.
Why does it sit outside the body?
Sperm production falters at core body temperature, so the testicles are held in a cooler compartment and kept there by three mechanisms working together. The cremaster muscle, a sling running down from the abdominal wall, lifts and lowers them. The dartos muscle in the scrotal skin wrinkles the surface in the cold to reduce heat loss and relaxes it in warmth to increase it. And a dense net of veins wrapped around the incoming artery cools arriving blood by exchanging heat with the cooler blood on its way out. The consequences of losing that arrangement are well documented: testicles that never descend and remain inside the abdomen produce far less sperm and carry a higher risk of cancer.
What is inside it?
| Structure | What it does |
|---|---|
| Testicle | Produces sperm and testosterone |
| Epididymis | A coiled tube along the back of each testicle where sperm mature and are stored |
| Spermatic cord | Carries the sperm duct, artery, veins and nerves up into the abdomen |
| Wall layers | Skin, the dartos muscle, and coverings continuous with those of the abdominal wall |
A midline ridge runs along the surface and a partition divides the interior, so each side is effectively its own compartment. The penis lies in front, and the two share their blood supply and nerve routes.
Why is it examined directly?
Because everything within it lies close to the surface, structures can be felt individually, and ultrasound produces clear pictures with no bone or gas in the way. That makes physical examination unusually informative here. Findings that are distinguished this way include a hydrocele, which is fluid collected around the testicle and transmits light; a varicocele, a bundle of dilated veins that feels like a bag of worms; inflammation of the epididymis; a hernia descending from the abdomen; and a firm mass within the testicle itself. Sudden severe pain is the exception to the usual pace, because a twisted spermatic cord cuts off blood supply and the window in which the testicle can be saved is short.
Used in a sentence
Physical examination of the scrotum revealed mild swelling on the affected side.
Good to know
Sudden severe scrotal pain raises the possibility of testicular torsion, a twisting of the spermatic cord that cuts off blood supply to the testicle, which makes it far more time sensitive than most other causes of scrotal pain.