- Your testicles make sperm. They sit under your penis in a bag called the scrotum.
- A series of narrow tubes take the sperm from your testicles toward your penis.
- Two sex glands add fluid to your sperm as they pass through the tubes. The fluid gives sperm energy and helps them to swim. The mixture of sperm and fluid is called semen.
- When you ejaculate, your penis pushes out the semen.
- Your urethra is a tube that carries both urine and semen out through your penis.
Testicles make up to 120 million sperm each day. The sperm become full-grown in about 10 weeks to 12 weeks.
Your testicles lie inside a pouch of skin called the scrotum. This hangs down outside your body because sperm grow best when the temperature is a few degrees lower than your body temperature.
When a male baby is growing in the womb, its testicles are inside its body. But as the baby grows, the testicles move downward. When the baby is born, the testicles are normally outside the body, in the scrotum. In some boys, the testicles stay inside the body. This can cause problems later, as a testicle left inside can't grow normally and can't make sperm.
Joined to each testicle is a tightly coiled tube (called the epididymis). Sperm are stored here once they have grown.
When you are sexually excited, the tubes in your testicles get narrower and squeeze sperm out. The sperm travel through a series of tubes toward your penis. The sex glands and the prostate add fluid to the sperm to make semen. The semen is pushed out of your penis through the urethra.
When you ejaculate, you normally release between 1.5 milliliters and 5 milliliters of semen.2 That's about one teaspoonful or less.
Because your urethra carries both semen and urine out of the body, the neck of the bladder (the sac that holds urine) normally closes during ejaculation. This prevents semen from going into the bladder and it also stops urine from getting into semen.
- Meniru GI. The male reproductive system. In: Cambridge guide to infertility management and assisted reproduction. Cambridge University Press, Cambridge, UK; 2001.
- American Urological Association Report on optimal evaluation of the infertile male. October 2001. Available at http://www.auanet.org/guidelines (accessed on 16 June 2008).
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This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved. |
