Erectile dysfunction, or male impotence, is defined as the persistent inability to maintain or to achieve an erection of sufficient rigidity to have satisfying sex. It is one of the most commonly untreated medical disorders in the world. Approximately 30 million men in the U.S. have problems achieving or maintaining an erection, and the frequency of ED increases with age.
Only one in twenty of these men seek treatment. Men are often embarrassed about being impotent, and prefer to avoid sex rather than seek help. This is unfortunate, because consistent loss of erection is not normal at any age. In addition, loss of erection can be a symptom of a serious medical illness, such as coronary disease or advanced vascular disease. Finally, there are many effective treatments available for this difficult condition.
The 2 structural compartments of the penis, the paired corpora cavernosa and the corpus spongiosum, are interspersed with a complex network of endothelial cell–lined lacunae, helicine arteries, and nerve terminals. The organ is innervated by somatic and autonomic nerve fibers.
The tunica albuginea is the dense, fibrous, elastic covering of the corpora cavernosa in the penis. During an erection, small penile blood vessels are compressed against the tunica albuginea, trapping blood in the penis and causing it to stay rigid.
Achieving an erection is a complex process. In a flaccid penis, there is a balance between blood flow in and out of the erection chambers. When a man becomes aroused, blood flow to the penis increases significantly. As the penis expands, pressure inside the penis increases and causes compression of veins that normally carry blood away from the penis. This limits the amount of blood that can flow out of the penis. With more blood flowing in and less blood flowing out, pressure increases in the penis; it enlarges and becomes fully erect.