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What is an erection?

Mark Moyad
Urology
An erection involves the concerted and coordinated actions of the brain and spinal cord (nervous system), blood vessels and hormones. This is why even a small abnormal function in one of these coordinated areas can cause problems, and also why sexual problems are so common.

Let’s review the actual effort involved in creating an erection (sound like a trip back to health education class?). The non-erect (flaccid) penis is under venous (as in vein) oxygen tension and pressure, which means not much is going on at the amusement park because the doors are not open yet. Erotic stimulation occurs, triggered by any one of many things. The brain and nervous system respond by quickly sending messages to the pelvic area causing the smooth muscles in the penis to relax. The blood vessels in the penis open wider due to compounds that are released, such as nitric oxide (NO), and this increases the blood flow into two parallel sponge-like cylinders (the corpora cavernosa), which run along the length of the penis on both sides. The corpora cavernosa are above the urethra, the passageway for urine and semen. As the cylinders fill with blood, they expand and press against the veins that would usually drain blood from the penis. This causes the penis to lengthen and swell, resulting in an erection (also called “tumescence”). During an erection, the penis is an arterial organ because fresh oxygenated blood has been pumped into it. After ejaculation or when sexual arousal has passed, the nervous system releases norepinephrine and other compounds, and blood actually drains out of the cylinders in the penis. The penis returns to its original size and shape (also called “detumescence”).
Dr. Moyad's Guide to Male Sexual Health: What Works and What's Worthless

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Dr. Moyad's Guide to Male Sexual Health: What Works and What's Worthless

There is perhaps no medical topic that is discussed less than male sexual health. True that it is the basis of countless tasteless jokes, but seldom is the subject approached in a frank and...

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.