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18 April 2014
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You are here: BBC Science > Human Body & Mind > The Body > Puberty

Rising to the occasion

Fountain
Fountain of joy

Also known as 'hard-ons' and 'stiffies', boys will begin to experience erections as soon as they start to mature sexually.

It can occur at quite a young age and even happens in some infants, although for different reasons. This functional, yet sometimes embarrassing, experience heralds the start of a boy's life as a fertile adult.

Erections are caused when blood flows to the penis. It builds up inside it causing pressure. Inside the penis are cavernous spaces that fill up with blood and cause swelling. The swelling, caused by this extra blood, blocks off the veins that normally take blood away from the penis.

When this happens, the blood pressure inside the penis rises dramatically and it enlarges and stiffens, pointing upwards. As an erection disappears, the arteries in the penis narrow again. Then the veins open, removing the blood again and the flow returns to normal.

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Ejaculation

Once the testicles begin to grow they also develop their adult function - producing sperm. Millions of sperm - maybe 120 million in a day - are created in tubes called 'seminiferous tubules'. These are connected to the base of the penis by a single tube called the 'epididymis'. Ejaculation occurs when sperm are forced out of the testes, along the epididymis, and out of the end of the penis. Between 200 and 400 million sperm are present in a single ejaculation.

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Strong urges

Erections can occur quite unconsciously in teenage boys - sometimes at quite inconvenient and embarrassing times. Boys often start masturbating around this time, as they explore new sexual experiences. If they don't masturbate they may still experience ejaculation during their sleep as a 'wet dream'. Most boys have orgasms before they first have sexual intercourse. For the first time, sexual feelings become strong urges which require conscious control.

Although boobs are the subject of many a boy's fantasy, many boys begin to develop breasts of their own during their teenage years.


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