What causes the penis to become erect?

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  1. Dr. Mehmet Oz
     
    Dr. Mehmet Oz answered:
    When a certain chemical reaction is triggered in the brain, it hops on a downtown express bus to start a ticker-tape parade in the loins. How? In a man, the signals from the brain trigger a reaction that causes blood to rush into the penis like Class V whitewater rapids.

    During stimulation, the muscles around the penis relax to let the blood in and be absorbed by a spongy structure on the top side of the penis called the corpus cavernosum. After the blood rushes in, the veins in the penis clamp down like a dam so the blood stays absorbed in the corpus cavernosum. All the while, a soft structure on the underside of the penis called the corpus spongiosum remains relaxed to allow semen to be released at ejaculation.

    Without proper blood flow-meaning that arteries are inflamed or clogged-men can't get an erection because they can't get blood in or keep it there. And that's one of the most common causes of erectile dysfunction-a condition that affects some 30 million American men.
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    When a certain chemical reaction is triggered in the brain, it hops on a downtown express bus to start a ticker-tape parade in the loins. How? In a man, the signals from the brain trigger a reaction that causes blood to rush into the penis like... More