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Testes
Gray's Anatomy (1918) plate, public domain
The testes are the two egg-shaped male glands, about 4-5 cm long, suspended in the scrotum. They make sperm — in tightly coiled seminiferous tubules, continuously from puberty — and testosterone, the main male hormone. Their position outside the body keeps them 2-3 degrees cooler than core temperature, which sperm production requires. Each testis is covered by tough protective layers and supplied by a cord of vessels, nerves and the vas deferens.
Key facts
- Sperm production takes about 70 days from start to finish within the tubules.
- The left testis usually hangs slightly lower than the right.
- Testosterone is made by Leydig cells between the tubules under control of the pituitary hormone LH.
- A muscle in the cord (cremaster) raises or lowers the testis to regulate its temperature.
What can go wrong
Testicular problems include lumps — testicular cancer is the commonest cancer of younger men and usually presents as a painless lump, so new lumps need prompt ultrasound — twisting of the cord (torsion), a surgical emergency with sudden severe pain; infections (epididymitis, often with urinary infections or STIs); and fluid or vein swellings (hydrocele, varicocele). Undescended testes in childhood are corrected to protect fertility and reduce cancer risk.
Related conditions
Related procedures & tests
Related symptoms
Related muscles
Frequently asked questions
Why are the testes outside the body?
Sperm production works best a few degrees below core body temperature; the scrotum's muscles and sweat response fine-tune that temperature.
What should I do if I find a testicular lump?
Have it examined promptly. Most lumps turn out to be benign cysts or fluid, but because testicular cancer is curable when caught early, an ultrasound is arranged quickly to check.
Educational information only. This atlas explains normal anatomy and describes conditions in general terms; it is not medical advice and does not replace assessment by a qualified clinician. If you have symptoms that worry you, seek medical care.
