Hesperian Health Guides
The Reproductive System in People Who Can Cause Pregnancy
HealthWiki > Where Women Have No Doctor > Chapter 4: Our Reproductive Bodies > The Reproductive System in People Who Can Cause Pregnancy
People who can cause pregnancy include men and boys with the body parts recognized as male at birth, as well as some people who do not identify as either men or women, and transgender women and girls. Like people who can get pregnant, they have reproductive organs on the outside and inside of their bodies, and the size, shape and color of the outside parts may differ for each person.
People who can cause pregnancy do so by making and delivering sperm. Sperm travel from the testicles through a tube where they become part of a fluid called semen. Semen comes out of the penis during sex, especially at climax. Each drop of semen has thousands of sperm, which are too small to see without a microscope. If sperm enters the vagina of a person who can become pregnant, it can combine with an egg to cause pregnancy.
Penis: This tube-shaped organ is made of spongy tissue and contains the urethra. The penis fills with blood and becomes stiff when the person is sexually excited.
Testicles (balls): The testicles begin to make sperm during puberty, and this continues for the rest of the person’s life. The testicles also make testosterone, a hormone that causes many of the physical changes of puberty. A person with testicles usually has two.
Scrotum: The testicles sit inside the scrotum, a sack of skin and muscle that hangs under the penis.
Vas deferens: These tubes carry sperm, mixed in semen, to the penis. When the vas deferens are cut in a vasectomy, sperm can no longer leave the person’s body.
Urethra: This tube carries semen out of the body when the person climaxes during sex. It also carries urine out of the body, from where it is stored in the bladder.