The penis contains two cylindrical, spongelike structures corpora cavernosa. During sexual arousal, nerve impulses increase blood flow to both of these cylinders. This sudden influx of blood causes an erection by expanding, straightening and stiffening the penis. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.
Whatever you happen to call it — todger, wang, willy, or dangler — the penis is an odd-looking bit of kit. But beyond the japes and sniggers, it is, of course, vital to the survival of our species. The penis is ancient. Penises are born ready. It is common for babies to exit the womb with an erection. Even before the moment of birth, ultrasound scans sometimes show a fetus with a fully formed erection.
When the blood vessels of the corpora cavernosa relax and open up, blood rushes in through the cavernosus arteries to fill them. The blood then gets trapped under high pressure, creating an erection. Sexual stimulation and friction provide the impulses that are delivered to the spinal cord and into the brain.
So many things have to go right for you to achieve a strong erection. For starters, your hormones must be released on demand, your arteries need to carry blood to the penis with perfect efficiency, your nervous system must transmit its signals without a hitch, and your mind must be working in perfect harmony with your body. If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.