Erectile dysfunction (ED) is the inability to get or keep a firm erection sufficient for sexual intercourse.
In an erection, impulses from the brain and local nerves cause the muscles of the corpora cavernosa, two chambers in the penis, to relax and allow blood to flow in through the arteries and fill the spaces. The engorged chambers expand the penis and the tunica albuginea, a membrane covering the two chambers, helps to sustain the erection. The erection ends when muscles in the penis contract to stop the inflow of blood and open the veins for blood outflow.
