Erection

Information about Erection

This article discusses human physiological erection. For erection of artificial structures, see construction.

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The erection of the penis, clitoris or a nipple is its enlarged and firm state. It depends on a complex interaction of psychological, neural, vascular and endocrine factors. The term is also applied to the process that leads to this state.

The ability to maintain the erectile state is key to the reproductive system and life itself could not reproduce in a natural way with out this ability.

In many countries, movies and magazines available to juveniles may not depict penile erection; 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 sexual intercourse, there are many slang words for an erection; see WikiSaurus:erection — the WikiSaurus list of synonyms and slang words for erection in many languages.

Penis erection

A penis erection occurs when two tubular structures that run the length of the penis, the corpora cavernosa, become engorged with venous blood. This may result from any of various physiological stimuli. The corpus spongiosum is a single tubular structure located just below the corpora cavernosa, which contains the 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. After a man has ejaculated during sexual encounter or masturbation, his erection usually ends, but this may take time depending on the length and thickness of the penis.

By actively contracting the Ischiocavernosus muscle at the base of the penis, a man can prolong his erection. Erection stays on because the sexual arousal is toned down by the pressure of this muscle on the surrounding tissue. The ejaculation is delayed by this. The author Gianni Venice proposes this method as best alternative to the stop-start technique, most often prescribed by sex therapists, to prevent premature ejaculation. According to Venice, the method to train the Ischiocavernosus is escpecially suited for younger men who do not have a spouse or partner to help them train the stop-start technique.

Penis erection usually results from sexual stimulation and/or sexual arousal, but can also occur by such causes as a full urinary bladder or spontaneously during the course of a day or at night, often during erotic or wet dreams (see "nocturnal penile tumescence"). An erection results in swelling and enlargement of the penis. Erection enables sexual intercourse and other sexual activities (sexual functions), though it is not essential for all sexual activities.

A circumcised penis flaccid (left) and erect (right).

In the presence of mechanical stimulation, erection is initiated by the parasympathetic division of the autonomic nervous system (ANS) with minimal input from the central nervous system. Parasympathetic branches extend from the sacral plexus into the arteries supplying the erectile tissue; upon stimulation, these nerve branches initiate the release of nitric oxide, a vasodilating agent, in the target arteries. The arteries dilate, filling the corpora spongiosum and cavernosa with blood. Erection subsides when parasympathetic stimulation is discontinued; baseline stimulation from the sympathetic division of the ANS causes constriction of the penile arteries, forcing blood out of the erectile tissue. The cerebral cortex can initiate erection in the absence of direct mechanical stimulation (in response to visual, auditory, olfactory, imagined, or tactile stimuli) acting through erectile centers in the lumbar and sacral regions of the spinal cord. The cortex can suppress erection even in the presence of mechanical stimulation, as can other psychological, emotional, and environmental factors. The opposite term is .

Shape and Size

An erect penis can take on a number of different shapes and angles, ranging from a straight tube angled at a 45-90 degree angle, to a curvature to the left or right, up or down. A tightly curved penis, known as Peyronie's disease, is identified by a severe curve in the erect penis. This may cause physical and psychological effects for the affected individual, which could include erectile dysfunction or pain during erection. Treatments include oral medication (such as Vitamin E) or surgery, which is most often reserved as a last resort.

Generally the size of an erect penis is fixed throughout post-pubescent life and little can be done to increase the size without modifying these tissues directly through surgery on the penis.

Clitoral erection

Clitoral erection is a part of sexual arousal in women. The clitoris is the anatomically homologous counterpart of the penis, and the physiological mechanism of its erection is similar.

Swelling and enlargement also occur during a clitoral erection but because a large proportion of the clitoris is within the body, it may not be obvious.

Nipple erection

Human female nipple in erect state.

Nipple erection may result from three kinds of response. It happens in females during breast feeding. It is also an early part of the sexual response in females and males. Both of these are caused by the release of oxytocin. Nipple erection can also be caused by cold temperature in both male and female. This is merely due to tactile response to cold temperature rather than anything linked to sexual drive. The erection of nipples is not due to erectile tissue, but due to the contraction of smooth muscle under the control of the autonomic nervous system. It is more akin to a hair follicle standing on end than to a sexual erection.

Bibliography

Drake, Richard, Wayne Vogl and Adam Mitchell, Grey's Anatomy for Students. Philadelphia, 2004. (ISBN 0-443-06612-4)
Harris, Robie H. (et al.), It's Perfectly Normal: Changing Bodies, Growing Up, Sex And Sexual Health. Boston, 1994. (ISBN 1-56402-199-8)
Milsten, Richard (et al.), The Sexual Male. Problems And Solutions. London, 2000. (ISBN 0-393-32127-4)
Tanagho, Emil A. (et al.), Smith's General Urology. London, 2000. (ISBN 0-8385-8607-4)
Williams, Warwick, It's Up To You: Overcoming Erection Problems. London, 1989. (ISBN 0-7225-1915-X)

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Anatomy

In the anatomy of mammals, a nipple or mammary papilla
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Slang is the use of highly informal words and expressions that are not considered standard in the speaker's dialect or language. Slang is often highly regional, specific to a particular territory.
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Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages.
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Corpus cavernosum can refer to:

corpus cavernosum clitoridis
corpus cavernosum penis

Though not used today, the term "corpus cavernosum urethrae" was used for corpus spongiosum in older texts.
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Physiology (from Greek: φυσις, physis, “nature, origin”; and λόγος, logos, "knowledge") is the study of the mechanical, physical, and biochemical functions of living organisms.
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Corpus spongiosum (Plural: Corpora Spongiosa) (also known as corpus cavernosum urethrae in older texts) is the mass of spongy tissue surrounding the male urethra within the penis.
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Corpus cavernosum can refer to:

corpus cavernosum clitoridis
corpus cavernosum penis

Though not used today, the term "corpus cavernosum urethrae" was used for corpus spongiosum in older texts.
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In anatomy, the urethra is a tube which connects the urinary bladder to the outside of the body. The urethra has an excretory function in both genders to pass urine to the outside, and also a reproductive function in the male, as a passage for sperm.
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Urine is a liquid produced by animals through the kidney, and is collected in the bladder and excreted through the urethra.

Urine formation helps to maintain the balance of minerals and other substances in the body.
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Semen is an organic fluid (also known as seminal fluid) that usually contains spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals for fertilization of female ova. The process of discharge is called ejaculation.
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Urination, known by physiologists as micturition, or more simply as voiding, is the process of disposing urine from the urinary bladder through the urethra to the outside of the body.
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Ejaculation is the ejecting of semen from the penis, and is usually accompanied by orgasm. It is usually the result of sexual stimulation, which may include prostate stimulation. Rarely, it is due to prostatic disease.
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In anatomy, the urinary bladder is a hollow, muscular, and distensible (or elastic) organ that sits on the pelvic floor in mammals. It is the organ that collects urine excreted by the kidneys prior to disposal by urination.
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nocturnal emission is an ejaculation of semen experienced by a male during sleep. It is also called a "wet dream", an involuntary orgasm, or simply an orgasm during sleep.

Nocturnal emissions are most common during teenage and early adult years.
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In anatomy and physiology, nocturnal penile tumescence is the spontaneous occurrence of a penile erection during sleep in the absence of any sexual stimulation. All men who are physically able to achieve erection do so during sleep, typically several times in a night^[1].
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Sexual intercourse or copulation is the union of the sex organs of two sexually reproducing animals.^[1] The two entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails.
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This article is about sexual practices (i.e., physical sex). Broader aspects of sexual behaviour such as social and psychological sexual issues are covered in related articles such as human sexuality, heterosexuality, and homosexuality.

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A model defining different aspects of sexual function relevant for the assessment of sexual dysfunction developed at the Karolinska Institute in Stockholm, Sweden, comprises the following components ^[1]
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parasympathetic nervous system (PSNS) is one of three divisions of the autonomic nervous system (ANS). The ANS -a subdivision of the peripheral nervous system (PNS)- is subdivided into the sympathetic (SNS), parasympathetic (PSNS) and enteric (bowels) nervous system (ENS).
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autonomic nervous system (ANS) (or visceral nervous system) is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These maintenance activities are primarily performed without conscious control or sensation.
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In human anatomy, the sacral plexus is a nerve plexus emerging from the sacral vertebrae (S1-S4), and which provides nerves for the pelvis and lower limbs.

Composition

The sacral plexus is formed by::

the lumbosacral trunk

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Arteries are muscular blood vessels that carry blood away from the heart.^[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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A vasodilator is a drug or chemical that relaxes the smooth muscle in blood vessels, which causes them to dilate. Dilation of arterial blood vessels (mainly arterioles) lead to a decrease in blood pressure.
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The Sympathetic Nervous System (SNS) is a branch of the autonomic nervous system. It is always active at a basal level (called sympathetic tone) and becomes more active during times of stress.
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cerebral cortex is a structure within the vertebrate brain with distinct structural and functional properties. In non-living, preserved brains, the outermost layers of the cerebrum has a grey color, hence the name "grey matter".
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• • [ e] Physiology, endocrinology, sex: Reproductive physiology and endocrinology
Menstrual cycle/Estrous cycle	Menstruation - Follicular phase - Ovulation - Luteal phase
Gametogenesis	Spermatogenesis -Oogenesis
Sexuality	Human sexual behavior - Sexual intercourse - Erection - Ejaculation - Orgasm - Insemination - Fertilisation/Fertility - Masturbation - Pregnancy - Postpartum period
Lifespan	Prenatal development - Sexual dimorphism - Sexual differentiation - Puberty (Menarche, Adrenarche) - Maternal age/Paternal age - Climacteric (Menopause, Andropause)
Eggs	Oviposition - Oviparity - Ovoviviparity - Viviparity

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