Erection

Erection is a stiffening and hardening of the penis which often occurs in the sexually aroused male (altough the penis may become erect because of other circumstances). Erection enables sexual intercourse, though it is not essential, and some other sexual activities.

Erection is achieved by influx of blood into a labyrinth of blood vessels within the corpus cavernosa in response to the increased sympathetic nerve supply (see autonomic nervous system). The vessels are distended, and reflex muscle contractions around veins trap blood in vessels of erectile tissue.

Both an erection and the absence of an erection can be embarrassing, depending on circumstances.

An erection may be embarrassing:

• if the man or boy does not want to reveal to another person that he is sexually aroused by him or her (or by a third person)
• if the erection is not caused by sexual arousal, but just by friction etc., and the man or boy does not want to create the wrong impression that he is sexually attracted by someone
• in a situation where an erection is inappropriate, such as in a classroom or a public place.

Not having an erection may be embarrassing:

• if a man or boy is with a partner and it wrongly creates the impression that he does not find the other person attractive

Also it may be disappointing for the partner because he or she finds an erection attractive, and disappointing for both for being limited in sexual activities.

When the erection mechanism fails to function properly, the result is impotence. Impotence in humans is treated with prosthetic[?] devices, and with prescription drugs. Some prescription drugs are injected directly into the corpus cavernosum or used as urethral suppositories, directly causing erection even in the absence of sexual excitation, while others, such as Viagra, are taken orally and support erection that is due to sexual excitation.

The clitoris also contains erectile tissue[?]; however, nipples do not.