| Normal erections require the coordinated actions of a healthy brain, pliable blood vessels, fully functional nerves, and certain hormones. Erotic stimulation, triggered by the five senses or by memory, begins the erectile process. The nervous system responds by sending chemical messages to and from the pelvic area.
These messages cause the smooth muscle tissue inside the penis to relax. The blood vessels dilate, allowing more blood to flow into the corpora cavernosa, the two erectile bodies within the penis. Like sponges, they capture more blood, swelling and lengthening the penis. When all of the spaces are occupied with blood, the organ becomes rigid. The enlarged corpora cavernosa take up so much space inside the penis that strong pressure is exerted against the penile veins, greatly reducing their outflow of blood.
At this point, the erect penis contains seven to eight times more blood than the same flaccid or non-erect penis. As long as the sexual stimulation is continued, an erect stage can be maintained until orgasm and ejaculation. |
