Physiology of Erection

In the anatomical structure of the internal part of penis we can distinguish two cylinder-shaped vascular tissue bodies (corpora cavernosa) that run through the penis, the urethra (tube for expelling urine and ejaculate); erectile tissue located around the urethra, two main arteries; and several veins and nerves. We do know that the longest part of penis body is a shaft with a head at its end, or so called glans penis. The opening at the end of the glans is known as meatus and it makes urination and ejaculation possible.

Thus, when we know the anatomical texture of penis we can come down to the physiological peculiarities of erection. It goes without saying that physiological process of erection starts in the brain and involves the work of nervous and vascular systems. Neurotransmitters in the brain (e.g., epinephrine, acetylcholine, nitric oxide) are some of the chemicals that work as initiators of it.

So, the combination of physical or psychological stimulation makes nerves to send messages to the vascular system which results in blood flowing to penis. Two arteries in the penis supply blood to erectile tissue and the corpora cavernosa, which become engorged and expand as a result of increased blood flow and pressure.

In order to let blood to stay in the penis to maintain rigidity, erectile tissue is enclosed by fibrous elastic sheathes (tunicae) that cinch to force blood to stay in the penis during the process of erection. When sexual stimulation comes to its end and is followed by ejaculation, the pressure in the penis starts decreasing, blood is released and penis resumes to its normal shape.