Planned Parenthood

Male Anatomy: Penis and Testicles

Planned Parenthood Teens Male Anatomy

Male anatomy at a glance:

  • During puberty, penises get bigger. But there isn't a normal size for any particular age.
  • Erections can happen when you're turned on (sexually excited), and at other times, too.
  • If you have any concerns about your penis or testicles, talk with an adult you trust.


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Is my penis normal?

Unless your penis hurts or feels uncomfortable, it's pretty safe to say it's normal. At some point during puberty, penises start to get bigger. This happens at different ages for different people, but it happens to everyone.

A lot of guys stress about the size of their penis, but there isn't a normal size for any particular age. The average adult erect (hard) penis is between five and seven inches long. The size of a guy's penis when it's flaccid (soft) doesn't really have anything to do with what it's like when erect. Some penises get much bigger when they become erect, and others stay pretty much the same size.

What’s the difference between uncircumcised and circumcised penises?

Uncircumcised penises have a foreskin that covers the head (tip) of the penis. When boys are circumcised, the foreskin is surgically removed. Uncircumcised and circumcised penises both work the same way; they just look a bit different.

Today, about half of boys in the U.S. are circumcised shortly after they are born, and about half are not. Circumcision may be more common in certain areas of the country than in others, or in certain cultures and religions.

Some people call circumcised penises “cut,” and uncircumcised penises “uncut.”

Guys who have uncircumcised penises may need to pull the foreskin back when they urinate, put on a condom, and wash their genitals.

What’s an erection, and why does it happen?

When someone with a penis is turned on (sexually excited), blood flows into his penis faster than it flows out. This causes the penis to get larger and harder, which is called getting an erection (sometimes called a hard-on or a boner).

Sometimes erections can happen at random times that you wouldn't choose, like when you're sitting in math class. Since you're probably not actually turned on by algebra, what's going on is called a spontaneous erection — an erection you get when you're not sexually aroused. Spontaneous erections can feel embarrassing, but they go away if you ignore them. They'll happen less frequently as you get older.

A sticky liquid spurts out of erect penises if men get very excited to the point of orgasm. This is called ejaculation or "coming." The liquid is called semen, ejaculate, or "cum," and it's not the same thing as urine. You cannot urinate (pee) and ejaculate at the same time.
It's possible to have an orgasm without ejaculating. It's also possible to ejaculate without orgasm. A hard penis becomes soft again after ejaculating.

Semen contains sperm. When sperm gets inside a woman's vagina, it can lead to pregnancy.

What’s a wet dream?

Ever wake up in the morning to find that you ejaculated in your sleep? This is called a wet dream, and it's completely normal, especially during puberty. Sometimes when you sleep, your penis gets hard and you ejaculate — maybe you had a sexy dream, or maybe your penis was stimulated when it rubbed against your sheets.

Most guys have wet dreams occasionally. As you get older, you'll get them less often. It’s also very common for a penis to become erect several times throughout the night, and to have an erection when you wake up (that’s where the term “morning wood” comes from).

What are testicles?

Testicles, or balls, are the body's sperm factory. Testicles make and store sperm, starting at puberty for the rest of your life. As if the testicles aren't busy enough, they also pump out testosterone — the hormone responsible for facial hair, bigger muscles, lower voices, and sex drive.

The sack that holds the two testicles is called the scrotum, and it's what keeps testicles at the right temperature. If it's too cold, the scrotum muscles bring the testicles closer to the body. If it's too warm, the muscles let the testicles hang away from the body. The scrotum often pulls testicles close to the body before ejaculation as well. The scrotum is covered with wrinkly skin and hair. Not all scrotums look exactly alike — they can be big or small, have a little or a lot of hair, and vary in color.

Even though many people call them "balls," testicles aren't exactly round — they're more oval-shaped, like an egg. Most guys have two testicles. Both testicles can hang at the same height, but most people have one lower than the other or one that's bigger than the other. Either way is perfectly fine.

Testicles are sexually sensitive. Many people enjoy having their scrotum and testicles gently rubbed or stroked. But for others, testicles are a "hands-off" zone.

Most people with testicles also know that they're pretty fragile — any hitting or twisting can be extremely painful. Protect your testicles during sports with a jock strap and cup. If you have sharp pain, itchiness, bumps, or any other changes on your scrotum or testicles, see a doctor, nurse, or other health care provider right away. It could be jock itch (a fungal infection), a serious condition called testicular torsion, or a sexually transmitted infection.

Although it's extremely rare, some teenagers do get testicular cancer. You can keep an eye out for this condition by getting regular sexual health checkups from your health care provider, and by feeling your testicles every now and then to learn what's normal for you so you can notice any changes.

What are blue balls?

"Blue balls" is a slang term for an uncomfortable or slightly achy feeling in the testicles. This can occur when a man gets an erection but doesn't ejaculate. Guys don't get blue balls every time they get an erection. Think of other times you've had an erection — it may have been a bit uncomfortable, but the discomfort goes away quickly.

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Male Anatomy: Penis and Testicles