How an erection works
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How an erection works
When the man is sexually stimulated, this sends nerve signals from his brain or, if he’s being touched, from nerve endings in his penis. These nerve signals affect the penis.
In the shaft of the penis there are two side-by-side chambers of spongy tissue called the corpora cavernosa. They're mainly responsible for erections. Just below them is another chamber called the corpus spongiosum.
When you get an erection, the nerve signals cause the smooth muscle of the chambers to relax and arteries to open wider. This allows a rush of blood to fill the empty spaces.
The pressure of blood flow causes the sheath of tissue around the chambers to press on veins that normally drain blood out of the penis. That traps blood in the penis.
As more blood flows in, the penis expands and stiffens, and you have an erection.
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