How does the reproductive system work?

A baby starts when a cell from the father (sperm) joins a cell from the mother (egg). This new cell keeps dividing and settles in the uterus, where it grows for about 9 months, getting food and oxygen from the mother through the umbilical cord.

Each month the uterus builds a soft inner lining to welcome a possible baby. If there is no pregnancy, the lining comes away and leaves through the vagina with a little blood over a few days. It starts at puberty, usually between ages 10 and 15, and is a sign of health.

It is a male gland just below the bladder that makes part of the fluid in semen. It wraps around the urethra, so when it grows with age it can interfere with peeing. From a certain age, doctors may recommend tests to keep an eye on it.

It is when a child’s body starts turning into an adult body, roughly between ages 8 and 14. Hormones make people grow faster and grow hair, deepen the voice (in boys), and start breast growth and periods (in girls). Everyone has their own pace.

In the lower belly, one on each side of the uterus, roughly between the belly button and the hip bone. Each is about the size of a large grape (just a size comparison).