The Male Body

At puberty, reproductive organs (sexual body parts) develop and mature. In boys, first the testicles or testes (balls) and then the penis will grow larger. Like all the changes you’ll have during puberty, these changes won’t happen all at once. Give yourself time. You will develop at your own pace.

Male Anatomy


The male sexual organ. Both semen and urine leave the body through the penis (but never at the same time!)


The fold of skin that may cover the end of the penis.


The tube that carries both urine or semen through the penis and out of the body.


Two oval glands that hang inside the scrotum. (Testicles are usually a bit lopsided, with one hanging a little lower than the other). The testicles produce sperm and the hormone testosterone.


The organ that holds urine (pee).

Seminal vesicles

Two small organs - one on each side of the prostate gland - that, with the prostate gland, add fluid to sperm to make semen.

Vas Deferens

The vas deferens are tubes that carry sperm from the testicles to the prostate gland.


The opening from which stool (poop) leaves the body during a bowel movement (BM).


Coiled tubes that are attached to the back of the testicles and connect with the vas deferens. Sperm are produced in the testicles, mature in the epididymis, and then move through the vas deferens to the prostate gland.


The sack of loose skin just behind the penis. The scrotum holds the testicles.

Prostate Gland

A gland that adds fluid to sperm to make semen.

Erection and Ejaculation

The basic function of the male sexual and reproductive system is to produce reproductive cells called sperm. Sperm leaves the body through a mixture of body fluids called semen.

When males are sexually excited (aroused), the penis becomes larger and stiffer and it usually stands out from the body. This is called an erection.

Many things can cause sexual arousal and an erection – even just looking at someone, or wearing pants that rub against the penis. Sometimes an erection can happen when you wake up in the morning with a full bladder.

When sexual arousal reaches its peak, males may have strong feelings of pleasure called an orgasm. During an orgasm muscles force semen out of the penis. This is called ejaculation. After ejaculation, the penis becomes soft again after a little time. It is possible to have an ejaculation without having an orgasm and it’s possible to have an orgasm without ejaculation. During ejaculation, the male body releases about one teaspoon of semen.

Not all erections end in ejaculation. If an erection doesn’t lead to ejaculation, the penis will get soft again.

Wet Dreams

Sometimes the penis can get erect and ejaculate semen while a male is asleep and dreaming. This is called a nocturnal emission (wet dream) and can happen to both boys and grown men. It can feel uncomfortable to wake up in damp pajamas and sheets, but wet dreams are natural. Not every boy has wet dreams and that’s ok too.

Size and Circumcision

Not all penises look the same. There are lots of different sizes of penises, and all sizes are healthy. Some boys’ penises look different from others because some are circumcised and some are not.

The decisions to circumcise or not circumcise may be due to cultural, religious or personal values of the family.

Size or circumcision does not affect how the penis works.

Circumcised and uncircumcised penises

?’s for boys

Why does a penis go hard ... is there a bone in it?

Nope. The penis is made of spongy tissue; there is no bone in it. During an erection the penis fills with blood and this makes it become hard.

Help ... am I growing breasts?

Boys also experience some small changes to their breasts during puberty. They may swell and hurt a little. Dont worry, this will stop after puberty.

Will I ever run out of sperm?

The average ejaculation contains 40 million sperm, but you will not run out. Each testicle makes millions of new sperm every day.

I’ve got an erection ... is it noticeable?

Some erections just happen for no reason at all. This can feel embarrassing, but these erections are natural. It’s not as noticeable as you think and goes away quickly.


The information contained in this section of the site is from the booklet Growing Up Okay! 
Reprinted with permission from Healthy Child Manitoba Office, 2013.