Studies show that 67% of men who are 70 years old have erectile dysfunction problems, while the ratio is 39% for men who are 40 years old; this means that there are approximately twenty million men have erectile dysfunction problems only in united States, therefore, with these rates, the problem was studied for many years, and there was different types of treatments, some of them were oral medicines, while others were physically, even some times it is surgically. But, to understand all of these treatments and the techniques they use, and to know the causes of erectile dysfunction problems, we should firstly understand the basic physiology of erection, or in other words, how it works.

The penis has two erection chambers called corpora cavernosa, these chambers are filled with spongy tissue called corporal sinusoids, which is the erectile tissue; this erectile tissue composed mostly of muscle. The erectile bodies and the smooth muscle in the penile arteries are responsible of erection and loss of erection by relaxing and contracting, respectively, to control the flow of the blood inside the penis. Although erection is regulated by hormones and nerves, it works in a hydraulic way; were the increase of blood flow into the erectile bodies and keeping the blood inside them increase the pressure inside the penis which harden it and cause erection. To trigger the penile erection, there are two mechanisms:

1. Stimuli coming from the brain (view, fantasy, smell …etc).
2. Direct stimulation of the genitalia.

The brain sends signals to the penis by passing it to the spinal cord, which in turn redirects them through special nerves (nervi erigentes) to the penis, these signals caused by some chemicals released in the brain when the man is stimulated, another chemical, called Nitric Oxide, is released by nerves; it causes the relaxation of the smooth muscle to allow the blood to flow into the erectile bodies, causing erection (as explained before).

Some psychological conditions may prevent the brain signals from reaching the required level for inducing erection, these conditions may be anxiety, fear, disgust …etc.

Also, some medical conditions, treatments, or therapies, may cause blocking or damaging of the erection arteries or cause scarring of the spongy erection tissue. In general, any problem that prevents blood from flowing properly into the erectile bodies will limit the erection. And as we can see, any damage of one of the previous components will cause erectile dysfunction problems.