Erection
- This article discusses physiological erection. For erection of artificial structures, see construction.
Erection of many tissues can occur in both sexes during sexual arousal. See, Human sexual response cycle.
Erection of the Penis
An erection of the penis occurs when engorgement of venous blood in two tubular structures at the bottom of the penis, the corpora cavernosa, results from a variety of stimuli. The corpus spongiosum is a single tubular structure located just above the corpora carvernonosa, and contains the male urethra, through which urine and semen pass during urination and ejaculation, respectively. This may also become slightly engorged with blood, but less so than the corpora cavernosa. Penile erection usually results from sexual stimulation and/or arousal, but can also occur by such causes as a full urinary bladder or spontaneously, most commonly during erotic or wet dreams. An erection results in swelling and enlargement of the penis or the swelling of the female counterpart to the penis, clitoris. Erection enables sexual intercourse and other sexual activities, though it is not essential for all sexual activities.
In addition to sexual arousal, erection in males can be caused by mechanical stimulation, or by the pressure of the filled urinary bladder. Erections when waking up are common, most likely due to a full bladder. They sometimes already occur in infant boys, and in utero. Recently some scientists have begun to doubt this very much (sources: see below). The question why most men have erections when waking up ("morning wood") is still not settled.
Mechanism
Physiologically, an erection is achieved by two mechanisms that play together: increased inflow of blood into the vessels of erectile tissue, and decreased outflow. The vessel system involved is known as the corpora cavernosa and the corpus spongiosum. Muscles in the region relax, allowing more blood to enter these sponge-like tissues. Contraction of other muscles reduce the outflow of blood from the penis. The enlarged structure then exerts pressures on the exit veins, further reducing the outflow.
As blood flows in, the penis stiffens, its girth and length increase and it rises to an angle that can vary between individuals from below horizontal to almost vertical.
Certain conditions (e.g. diabetes mellitus) result in erectile dysfunction, a problem where penile erection is insufficient to achieve normal sexual intercourse. In recent years, several drugs have been developed for treatment of this condition.
If present, the foreskin normally retracts and exposes the glans. The skin of the scrotum tightens, pulling the testicles in towards the base of the penis.
Erection is caused by signals from the parasympathetic nervous system; it is countered by the sympathetic nervous system which is mainly responsible for the "fight-or-flight" response. This explains why under stressful conditions, an erection is often difficult or impossible to achieve, and sudden onset of stress can deprive one of erection. The sympathetic nervous system is also responsible for causing ejaculation, which explains why most males lose their erection after ejaculation.
Erection may occur spontaneously in the absence of any specific sexual stimulation, particularly in adolescent males. All men who are physically able to achieve an erection do so during sleep, typically several times in a night. This fact is utilized by sexual health practitioners to ascertain whether cases of erectile dysfunction are psychological or physiological in nature. Patients presenting with impotence are fitted with an elastic device worn around the penis which detects changes in girth and relays the information to a computer for later analysis. Men who obtain spontaneous erections in their sleep but not during waking hours are therefore considered to suffer from some form of psychosomatic condition, i.e. sexual anxiety disorder, which prevents them performing sexually.
Masturbation has no negative impact of erectile function besides a reduction in sex drive in a way exactly homologous to sexual intercourse.
In some cases penile erection may occur even after death, if pressure within the penis increases for some reason, for example due to sinking fluids or the formation of gases of putrefaction. See death erection.
The clitoris of females contains erectile tissue and becomes erect during sexual arousal. Erection of the clitoris is exactly analogous to male penile erection only less visible due to the relatively discreet anatomical positioning of the clitoris.
Erection of nipples, however, is not due to erectile tissue.
Dysfunction
Failure of the erection mechanism is known as erectile dysfunction, or ED for short. ED 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, Cialis, or Levitra are taken orally and support erection that is due to sexual excitation.
Occasionally, the foreskin of the erect penis may be very tight and immobile on the shaft, thus interfering with normal erection. This condition is known as phimosis, however it is usually very easily treatable.
Culture
In several countries, movies and magazines available to juveniles may not depict erections; such depictions are often taken as one criterion to distinguish between soft and hard pornography.
Slang
As with nearly any aspect of the human body that is involved in sex, there are many slang words for an erection. Some of these are noted in the bathroom humor article.
- For slang terms for the "erection", see WikiSaurus:erection — the WikiSaurus list of synonyms and slang words for erections in many languages.
Some terms would be (in alphabetical order): blood sport, boner, johnson, peter, stiffy, wang, woody, love truncheon
Bibliography
- Harris, Robie H. (et al.), It's Perfectly Normal: Changing Bodies, Growing Up, Sex And Sexual Health. Boston, 1994. (ISBN 1564021998)
- Milsten, Richard (et al.), The Sexual Male. Problems And Solutions. London, 2000. (ISBN 0393321274)
- Tanagho, Emil A. (et al.), Smith's General Urology. London, 2000. (ISBN 0838586074)
- Williams, Warwick, It's Up To You: Overcoming Erection Problems. London, 1989. (ISBN 072251915X)
See also
External links
- Photographs of several different erections by size, shape, angle, etc. from a photographic scientific study (The images are explicit, but scientifically presented, rather than pornography)