THE EPIDIDYMIS AND THE VAS DEFERENS
After the sperm are made, they travel from the tubules inside the testicle to the epididymis, a special compartment attached to the testicle. The epididymis is also composed of tiny tubes. It is here, inside these tubes, that the sperm ripen into mature sperm. It takes the sperm about four to six weeks to travel through the epididymis, during which time they complete their ripening.
The vas deferens-Once they’re fully mature, the sperm are ready to travel out of the scrotal sac and up into the body, where they are stored until you ejaculate. To get from the scrotum to the main part of your body, the sperm travel through a tube called the vas deferens (also called the vas or sperm duct). You have two sperm ducts, one for each testicle. Each one is 355-455 mm (14-18 in) long.
Perhaps you’ve wondered why the testicles and scrotum hang down, outside and away from the main part of your body. As one boy in our class put it:
Why do they dangle down there like that where they can get hit and knocked about? Why aren’t they tucked up inside your body where they’d be safe?
It’s a good question, and there’s a good answer. In order for your testicles to make sperm, they have to be at exactly the right temperature. The right temperature is a little lower than the temperature of the rest of your body. If your testicles were up inside your body, they’d get too hot to make sperm. So, instead, they hang down in the scrotal sac, away from your body. This way air can circulate around them and keep them cool. In cold weather or when you jump into cold water, the scrotum tightens up, bringing your testicles closer to your body for extra warmth. In hot weather, after a hot bath or when you have a fever, the scrotum relaxes and hangs lower so that your testicles are farther away from your body and can stay cool.
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