What is an erection and how does it work?

What is it?

Erection is a natural function of the body where the 2 tubular structures that run along the length of the penis, the corpora cavernosa, are filled up with venous blood. An erection makes the penis to harden up and stand away from the body.

This may happen because of some stimuli, and is known as sexual arousal. It sounds simple enough but it is a complicated process which involves the autonomic nervous system and the central nervous system. When erection is caused due to mechanical stimulation of the penis, the autonomic nervous system is involved.

Different types of stimulation

There are different types of stimulation that can get the penis erect. It could be auditory, olfactory, visual, imagined or tactile stimuli. All these send signals to the cerebral cortex which initiates erection. The erectile centers in the lumbar and sacral areas of the spinal cord then signal the nerve branches to release nitric oxide in to the arteries that supply blood to the penis.

Nitric acid is a vasodilating agent. Then the arteries dilate and fill the corpora cavernosa with more blood than normal. Then the two sponge-like tissues expand in size and hold a lot of blood inside them. The Corpus Spongiosum, which is another tubular structure located below the Corpora Cavernosa and which acts as the outlet for the semen and urine, also gets filled with blood, although, this engorgement is not as much as the Corpora Cavernosa.

The mechanism

Once the blood is filled in the penis, the arteries then contract and return to their normal flow of blood. This normal blood flow of the arteries prevents the blood in the penis from getting out, which in turn keeps the penis erect. The same process happens even when the penis is mechanically stimulated without any external stimuli present.

The complete process of penis erection is taken care of by the autonomic nervous system and with very less activity from the central nervous system. Once the stimulation stops, the autonomic nervous system makes the arteries to constrict and the blood is then forced out of the penis, making the penis flaccid.

In spite of the cerebral cortex not being involved in all types of stimulation that cause erection, it does have the power to stop or put an end to an erection, if it feels that the situation warrants that action. This is the reason why, when having sex or during foreplay, men and women avoid circumstances or talking about anything that will "put them off", which means losing interest and erection.


If you understand the process of erection and how to maintain it, it helps with having better sex and ensuring you create the perfect setting for a wonderful sex experience with your loved one.


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