In order to have a net increase in blood flow, Ramin said these four crucial steps must take place: Adam Ramin, MD, urologic surgeon and medical director of Urology Cancer Specialists.

“Erections occur when there is a net increase of blood flowing into, as compared to blood exiting, the erectile spongy bodies of the penis,” said S. And it can help you understand why Viagra may not be working.

Becoming aroused is a complex combination of factors - from physical responses to mood and emotions - so it’s important to understand the physiology of an erection.