Let's be honest, we all know what an erection is and if you don't there's a good chance that you're too young to be looking this up anyway. An erection happens when two tubes that run down the length of the penis become inflated with venous blood. This, more often than not, only happens when you are (physically or psychologically) sexually aroused. Urine and semen both pass through the urethra, which is located in the corpus spongiosum, this can also become engorged but never to the same extent. After a man has ejaculated his erection ends and begins to become flaccid, the time it take to become flaccid it relative to the length and thickness of the penis.

The penis can take on a number of different shapes and angles when it becomes erect although the size of the penis doesn't change throughout the post-pubescent years of development. A tight curve in the penis is called Peyronie's disease, which can lead to pain during erections and erectile dysfunction. Erectile dysfunction is the inability to have or keep and erection. Cardiovascular leakage or diabetes are common conditions linked with erectile dysfunction. Now, I hope I don't offend anyone but around 1 in every 10 men suffers from prolonged impotence problems at one stage in their life.An erection can be the result of sexual arousal, spontaneously during sleep or due to a full bladder. Obvious side effects of an erection include hardening; swelling, enlarging of the penis and the scrotum can also become tightened. All these are essential for penis during sexual intercourse.

A little known fact is that the consciousness center of our brain can control whether you have an erection or not. It can raise an erection if there isn't any stimulation and can suppress it if there is. Weird as it is, scientists are still puzzled why this autonomic control has been placed into our brain.