Viagra quiz

Mallika Sherawat

How does a penis become erect?
The penis becomes erect when its two cigar-shaped tubes called corpora cavernosa (singular: corpus cavernosum) fill with pressurized blood.

How does the blood flow to the penis change during an erection?
When a man becomes aroused sexually, the arteries in his penis expand and the veins contract. This leads to a net gain of blood -- and an erection.

The first drug developed to treat erectile dysfunction was called phentolamine. How was it originally demonstrated?
In front of urologists attending the 1983 American Urological Association Meeting, Dr. Giles Brindley did indeed drop his pants after injecting his penis with phentolamine. The first-ever, drug-induced erection wowed the crowd, and proved that erectile dysfunction is not primarily all in the head.


What were the down sides of phentolamine that lead to further research in treating erectile dysfunction and the development of Viagra?


Phentolamine causes an instant and uncontrolled erection -- not always the most sure-fire way to impress the ladies, and a little awkward if something besides love-making suddenly comes up.
Phentolamine has to be delivered via an injection because it affects a common type of muscle tissue -- smooth muscle -- that's not unique to the penis in particular. As a pill, it could cause problems for smooth tissue in other parts of the body like the intestines and blood vessels.

Let's get back to the arteries and veins in the penis. Under normal circumstances, how do they know when to expand and contract?
As long as a man is aroused, his brain will continue triggering this simple chemical reaction that acts like an on/off valve. Nerve endings in the penis' corpora cavernosa receive signals to release nitric oxide, nearby enzymes react by producing cGMP (cyclic guanosine monophosphate), and this chemical tells the smooth muscles in the artery walls to relax and expand.