Mechanism of erection

When discussing the problems with erection, it should be remembered that they are an end effect of a complex process, constituted by psychological, neurological, hormonal, and vascular factors. For a better understanding of the pathogenesis of this process, it is important to know that the penis is composed of three basic anatomical structures – two longitudinal cavernous bodies (a kind of chambers) and one spongy body, including the urethra. These are the cavernous bodies that (supplied by respective arteries) increase their volume during erection, owing to the inflowing blood. It is also worth knowing that arteries (as opposed to veins) have their muscular layer composed of smooth muscles which – by dilation or contraction – regulate the blood flow.

Fig. Mechanism of erection

The whole process starts with sexual arousal. This is when the increasing activity of some specific components of the autonomic nervous system stimulates the release of neurotransmitters at nerve endings in the cavernous bodies or in the endothelium of the arteries. This leads to secretion of NO – nitric oxide, which is one of the strongest smooth muscle relaxants. With dilated cavernous arteries, the amount of blood flowing into the penis increases, and its outflow is hindered by a physiological compression of some specific veins. Moreover, contraction of the ischiocavernous muscle stabilises the penis in erectile position. A key factor of effective erection is the condition of the vascular system, ensuring a proper perfusion of the reproductive organs. Any pathologies of this system (e.g. atherosclerosis, coronary disease, hypertension) lead to problems with erection.