Sexual intercourse (human)


 * This article is about sexual intercourse in humans and its societal implications. For biological copulation in general, see copulation.







Sexual intercourse, specifically coitus, is the human form of copulation. The term sexual intercourse refers to a wider range of sexual activities than the term coitus, which only refers to male-female genital sex. See Human sexual behavior for a discussion of the broader sense of sexual intercourse and list of sexual positions for the wide variety of sexual activities that exist. See the terms frot for male-male genital sex and tribadism for female-female genital sex. "Genital sex" as used here refers to genito-genital sex, among BDSM/fetish practitioners the term "genital sex" can mean any sex involving the genitals including anal, oral, manual etc., as opposed to those based on toys, costumes or fantasies.

Coitus may be preceded by foreplay, which leads to sexual arousal of the partners, resulting in the erection of the penis and natural lubrication of the vagina.

To engage in sexual intercourse, the erect penis is inserted into the vagina and one or both of the partners move their hips to move the penis backward and forward inside the vagina to cause friction, without ever fully removing the penis. In this way, they stimulate themselves and each other until orgasm and ejaculation are achieved. Penetration with the penis is also known as intromission, or by the Latin name immissio penis.

A detailed description of the physiology of sexual arousal and orgasm can be found in the article Human sexual response cycle.

Sexual reproduction
Coitus is the basic reproductive method of humans. During ejaculation, which normally accompanies male orgasm, a series of muscular contractions delivers semen containing male gametes known as sperm cells or spermatozoa into the vault of the vagina. The subsequent route of the sperm from the vault of the vagina, is through the cervix and into the uterus, and then into the fallopian tubes. Millions of sperm are present in each ejaculation, to increase the chances of one fertilizing an egg or ovum. Sperm cells can survive up to nine days in the female body. When a fertile ovum from the female is present in the fallopian tubes, the male gamete joins with the ovum resulting in fertilization and the formation of a new embryo. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus, known as endometrium and a pregnancy begins.

Male-female coitus should always be considered likely to result in pregnancy unless adequate contraceptive (birth control) measures are in force, or unless one (or both) of the partners is not fertile. For example a woman who has passed through menopause cannot conceive, but can still participate in, and enjoy, intercourse. When both participants are believed to be fertile, pregnancy should still be considered as a possible outcome of intercourse, because no birth control measure is 100 percent effective. A prophylactic such as a condom is among the most effective methods of birth control short of sterilization or abstinence, with effectiveness rates in the high 90th percentiles. Coitus interruptus, or withdrawal of the penis from the vagina just before the man's orgasm, typically has a high failure rate, as sperm are usually present in pre-ejaculate in sufficient quantities to pose a significant risk of pregnancy. Surgical sterilization (tubal ligation for women or vasectomy for men) is considered permanent birth control, though it can sometimes be reversed surgically, or, rarely, the body can repair itself. If both partners are fertile, abstinence from heterosexual intercourse is the only 100 percent effective way to avoid pregnancy. Outercourse, and other sexual contact (such as mutual masturbation or oral sex), in which there is sexual activity without penis insertion, can be performed without resulting in pregnancy provided that semen does not come in contact with the vulva.

Sex evolving beyond reproduction
Humans, bonobos and notably dolphins are all species known to have non-reproductive sex, apparently for the sake of pleasure. All three engage in heterosexual behaviors even when the female is not in estrus, that is, at a point in her reproductive cycle suitable for successful impregnation. Likewise, all three engage in homosexual behaviors. That is not to say that homosexuality and non-reproductive heterosexuality are limited to these three species; rather, they are unusual for female receptivity to sex independent of estrus.

In both humans and bonobos the female undergoes concealed ovulation, so that males do not know whether she is fertile at any given moment. The evolutionary advantage encourages sex anytime for social reasons rather than reproductive ones. The presence of one or more emotionally committed adults assists the female in cooperative tasks, such as raising offspring.

Humans, bonobos and dolphins are all intelligent social animals, whose cooperative behavior proves far more successful than that of any individual alone. In these animals, the use of sex evolved beyond reproduction to serve additional social functions. It may be that sex reinforces intimate social bonds between individuals to form larger social structures. The resulting cooperation encourages collective tasks that promote the survival of each member of the group.

Sexual drive
The urge of adult humans to have sexual intercourse is generally seen as being a physiological need similar to needs such as food, water and air. See, for example, Maslow's hierarchy of needs.

At an emotional level sexual intercourse is often, though not always, the ultimate physical expression of feelings of romantic love between two humans. In many cultures, mutual romantic love often forms a formalized or informal partnership, a full sexual relationship within this partnership, procreation or adoption of children and parenting. Romantic love is not limited to those of opposite sexes, and also occurs among those of the same sex.

However, sexual intercourse is also often decoupled from romantic love and/or from a wish for procreation. Casual sex often used to satisfy a physiological need is common, although it is censured by some as being promiscuous and morally questionable. The sex industry is the commercialization of casual sex; this industry includes prostitution.

Downside of sexual intercourse
While being well suited for effective stimulation of the penis, intercourse is poorly suited for effective stimulation of the clitoris. Many women (perhaps as many as 70 percent) rarely or never have orgasms during intercourse without simultaneous direct stimulation of the clitoris. Disregard of this fact is the most common cause of female anorgasmia.

Sexual problems
Some males suffer from erectile dysfunction, or impotence, at least occasionally. For those whose impotence is caused by medical conditions, prescription drugs such as Viagra, Cialis, and Levitra are available. However, doctors caution against the unnecessary use of these drugs because they are accompanied by serious risks such as increased chance of heart attack. Also, using a drug to counteract the symptom--impotence--can mask the underlying problem causing the impotence, and does not fix the problem. A serious condition might be aggravated if left untreated.

A more common sexual disorder in males is premature ejaculation (PE). Those afflicted with PE can perform intercourse for an average of 1.8 minutes before experiencing an orgasm. This compares with an average of 7.3 minutes for those not suffering from premature ejaculation. The U.S. Food and Drug Administration (FDA) is examining the drug dapoxetine to treat premature ejaculation. In clinical trials, those with PE who took dapoxetine experienced intercourse three to four times longer before orgasm than without the drug.

The American Urological Association (AUA) estimates that premature ejaculation could affect 27 to 34 percent of men in the United States. The AUA also estimates that 10 to 12 percent of men in the United States are affected by erectile dysfunction.

Inability to achieve orgasm is called anorgasmia. It is much more common in women than men and usually needs attention from both partners over a long time span to solve. Many women, especially younger women with little sexual experience, have difficulty achieving orgasm. Whether a woman considers anorgasmia a problem or not is highly individual; the popular but dubious notion that both partners should achieve orgasm in "normal" intercourse may contribute to a woman's concern over anorgasmia.

Vaginismus is involuntary tensing of the pelvic floor musculature, making coitus distressing or impossible. Dyspareunia is painful or uncomfortable intercourse; it can be due to a variety of reasons.

Sexual morality and legality
Various laws, moral rules, and taboos surround sexual intercourse. See sexual morality for a detailed discussion.

Unlike some other sexual activities, sexual intercourse has rarely been made taboo on religious grounds or by government authorities. It is believed that all of the cultures that prohibited sexual intercourse entirely no longer exist, save the Shakers, a sect of Christianity that has very few adherents, though there are many communities within cultures that prohibit their members to engage in any form of sex, such as members of religious orders and the priesthood in the Roman Catholic Church and lamas in Buddhist monasteries. Within some ideologies, coitus has been considered the only "acceptable" sexual activity. Relatively strict designations of "appropriate" and "inappropriate" sexual intercourse have been almost universal in human societies. These have included prohibitions against specific positions, against intercourse among partners who are not married (this is called fornication) or at least one of whom is married, but not to each other (called adultery), against sexual intercourse with a close relative (called incest), and against intercourse during a woman&rsquo;s menstrual period.

Often a community adapts its legal definitions during case laws for settling disputes. For example, in 2003 the New Hampshire Supreme Court ruled that same-sex relations do not constitute sexual intercourse, based on a 1961 definition from Webster's Third New International Dictionary in Blanchflower v. Blanchflower, and thereby an accused spouse in a divorce case was found not guilty of adultery based on this technicality.

Most countries have age of consent laws specifying the minimum legal age for engaging in sexual intercourse. Sexual intercourse with a person against his or her will, or without their informed legal consent, is called rape and is considered a serious crime in most cultures.

Religions have often established standards and mores for sexual intercourse, usually encouraging monogamy and marriage. In the Christian faith, sex outside marriage is officially condemned with varying degrees of severity. This prohibition on sex solely for pleasure has led to the Roman Catholic Church’s highly controversial condemnation of artificial forms of contraception. See (for example)

There is a good deal of controversy about the kind of relationship one should have with someone else before engaging in sexual intercourse. This controversy is beyond the scope of this article; interested readers are encouraged to read the articles on chastity, evolutionary psychology, and sexual morality.