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Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which the male reproductive organ enters the female reproductive tract. The two entities may be of opposite sexes or not, or they may be hermaphroditic, as is the case with snails. In recent years, penetration of non-sexual organs (oral intercourse, anal intercourse) or by non-sexual organs (fingering, fisting) are also sometimes included in this definition. Traditionally, intercourse has been viewed as the natural endpoint of all sexual contact between a man and a woman.
Non-penetrative sex (oral sex may or may not be penetrative) and mutual masturbation have been referred to as "outercourse". "Outercourse" is something of a misnomer, as it contrasts "outer" with "inter" but the "inter" in "intercourse" means "between two people" or beings. It does not describe being inside or outside of the body. The word sex, in the context of sexual intimacy, is often, if not universally, understood to include any mutual genital stimulation, i.e. both intercourse and outercourse.
Mating is the term most often used to refer to sexual intercourse between animals other than humans; for most, mating occurs at the point of estrus (the most fertile period of time in the female's reproductive cycle), which increases the chances of successful impregnation. However, bonobos, dolphins, and chimpanzees are known to engage in sexual intercourse even when the female is not in estrus, and to engage in sex acts with same-sex partners. In most instances, humans have sex primarily for pleasure. This behavior in the above mentioned animals is also presumed to be for pleasure, which in turn strengthens social bonds.
Modern Judaism, Christianity, and Islam view sexual intercouse between husband and wife as a spiritual and edifying action, while extra-marital sex is viewed as immoral. The limits of marriage and concubinage within these traditions has changed over time, along with corresponding views of acceptable sexual behavior. The teachings of Hinduism and Buddhism on sexuality have differing interpretations, though mostly they are associated with marriage. Buddhism's injunction to "refrain from sexual misconduct" finds its interpretation and practical definitions within the particular Buddhist communities. However, within each of these major religious traditions exists subgroups with varying stances on acceptable sexual practices, and some religious groups prohibit their members from engaging in sexual intercourse altogether.
Many animals which live in the water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptiles, some fish, and most birds) occur via cloacal copulation (see also hemipenis), while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.
However, some terrestrial arthropods do use external fertilization. For primitive insects, the male deposits spermatozoa on the substrate, sometimes stored within a special structure, and courtship involves inducing the female to take up the sperm package into her genital opening; there is no actual copulation. In groups such as dragonflies and spiders, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female (in dragonflies, it is a set of modified sternites on the second abdominal segment; in spiders, it is the male pedipalps). In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a "spermatophore") into the female's reproductive tract.
Vaginal sexual intercourse, also called coitus, is the human form of copulation. While its natural purpose and result is reproduction, it is often performed entirely for pleasure and/or as an expression of love and emotional intimacy. Sexual intercourse typically plays a powerful bonding role; in many societies it is normal for couples to have frequent intercourse while using birth control, sharing pleasure and strengthening their emotional bond through sex even though they are deliberately avoiding pregnancy.
Sexual intercourse may also be defined as referring to other forms of insertive sexual behavior, such as oral sex and anal intercourse. The phrase to have sex can mean any or all of these behaviors, as well as other non-penetrative sex acts not considered here. Sex positions often play a part in all human sexual interactions.
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 coitus, 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, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved. Penetration by the hardened erect penis is also known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis").
Coitus is the basic reproductive method of humans. During ejaculation, which usually accompanies male orgasm, a series of muscular contractions delivers semen containing male gametes known as sperm cells or spermatozoa from the penis into 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. 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.
Unlike most species, human sexual activity is not linked to periods of estrus and can take place at any time during the reproductive cycle, even during pregnancy.
Anorgasmia is regular difficulty reaching orgasm after ample sexual stimulation, causing personal distress. This is much more common in women than men. The physical structure of the act of coitus favors penile stimulation over clitoral stimulation. The location of the clitoris then often necessitates manual stimulation in order for the female to achieve orgasm. About 15 percent of women report difficulties with orgasm, and as many as 10 percent of women in the United States have never climaxed. Even women who orgasm on a regular basis only climax about 50 to 70 percent of the time.
Some males suffer from erectile dysfunction (ED), 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. Moreover, using a drug to counteract the symptom—impotence—can mask the underlying problem causing the impotence and does not resolve it. A serious medical condition might be aggravated if left untreated.
A more common sexual disorder in males is premature ejaculation (PE). The U.S. Food and Drug Administration 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. Another ejaculation-related disorder is delayed ejaculation, which can be caused as an unwanted side effect of antidepressant medications such as Fluvoxamine.
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. Vaginismus is involuntary tensing of the pelvic floor musculature, making coitus distressing, painful, and sometimes impossible. Dyspareunia is a medical term signifying painful or uncomfortable intercourse, but does not specify the cause.
Although disability-related pain and mobility impairment can hamper intercourse, in many cases the most significant impediments to intercourse for individuals with a disability are psychological. In particular, people who have a disability can find intercourse daunting due to issues involving their self-concept as a sexual being, or partner's discomfort or perceived discomfort.
Temporary difficulties can arise with alcohol and sex as alcohol initially increases interest (through disinhibition) but decreases capacity with greater intake.
Functions of sex beyond reproduction
Sex between cohabiting partners lowers blood pressure and reduces stress, according to Stuart Brody, professor of psychology at the University of the West of Scotland. Brody's team monitored 24 women and 22 men who were exposed to stressful situations, such as speaking in public and doing verbal arithmetic, and kept records of their sexual activity. The men and women who had penile-vaginal intercourse responded more positively to stress "than those who engaged in other sexual behaviors or abstained". A study by Keith Light of the University of North Carolina went as far as to find a link between "partner hug" and lower blood pressure in women.
Frequent sexual intercourse was held to reduce the risk of the common cold by Carl Charnetski and Francis X. Brennan of Wilkes University in Wilkes-Barre, Pa. These scientists linked frequent sexual intercourse (once or twice a week) to increased production of the antibody called Immunoglobulin A or IgA, which can protect the body from getting colds and other infections. They took samples of saliva, which contain IgA, from 112 college students who reported the frequency of sex they had. The students in the "frequent" group had higher levels of IgA than those in the other three groups, consisting of people who were celibate, had sex less than once a week, or had it "very often" (three or more times weekly). The other three groups had comparable IgA levels. Charnetski and Brennan had previously shown that exposure to elevator music has a similar effect on IgA levels.
"Sex is a great mode of exercise," according to Patti Britton, PhD, past president of the American Association of Sexuality Educators, Counselors and Therapists (AASECT) and currently host of the website "Your Sex Coach". She notes that thirty minutes of sex burns 85 calories or more. She concludes that 42 half-hour sessions, or 21 hour-long sessions, will burn 3,570 calories - sufficient to lose one pound.
"Boosting self-esteem" was one of 237 reasons people have sex, collected by University of Texas researchers and published in the journal Archives of Sexual Behavior. Some subjects who already had high self-esteem said they sometimes have sex to "feel even better".
Sexual intimacy, as well as orgasms, increases levels of the hormone oxytocin, also known as "the love hormone" which helps people bond and build trust. Researchers from the University of Pittsburgh and the University of North Carolina at Chapel Hill evaluated 59 premenopausal women before and after warm contact with their husbands and partners ending with hugs. They found that the more contact, the higher the oxytocin levels. Oxytocin allows people to feel the urge to nurture and to bond. Generosity has also been credited and linked to a higher level of oxytocin. In addition, as the hormone oxytocin surges, endorphins increase, and pain declines. In a study published in the Bulletin of Experimental Biology and Medicine, 48 volunteers who inhaled oxytocin vapor and then had their fingers pricked lowered their pain threshold by more than half. The oxytocin released during orgasm also promotes sleep.
Men who have frequent ejaculations, especially men in their 20s, may reduce their risks of prostate cancer later in life. Australian researchers reported in the British Journal of Urology International that they followed men diagnosed with prostate cancer and those without. They found no association of prostate cancer with the number of sexual partners as the men reached their 30s, 40s, and 50s, but men who had five or more ejaculations weekly while in their 20s reduced their risk of getting prostate cancer later by a third. Another study, reported in the Journal of the American Medical Association, "found that frequent ejaculations, 21 or more a month, were linked to lower prostate cancer risk in older men, as well, compared with less frequent ejaculations of four to seven monthly".
During sex, pelvic floor muscle exercises known as Kegels offer benefits for women. More sexual pleasure is expected to result, strengthening of the area, and help to minimize the risk of incontinence later in life.
Social and other behaviors
Humans, bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species, and others, are also known to engage in homosexual behaviors.
In both humans and bonobos, the female undergoes relatively concealed ovulation so that both male and female partners commonly do not know whether she is fertile at any given moment. One possible reason for this distinct biological feature may be formation of strong emotional bonds between sexual partners important for social interactions and, in the case of humans, long-term partnership rather than immediate sexual reproduction.
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 has evolved beyond reproduction apparently to serve additional social functions. 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.
Alex Comfort and others posit three potential advantages of intercourse in humans, which are not mutually exclusive: reproductive, relational, and recreational. While the development of the Pill and other highly effective forms of contraception in the mid- and late 20th century increased people's ability to segregate these three functions, they still overlap a great deal and in complex patterns. For example: A fertile couple may have intercourse while contracepting not only to experience sexual pleasure (recreational), but also as a means of emotional intimacy (relational), thus deepening their bonding, making their relationship more stable and more capable of sustaining children in the future (deferred reproductive). This same couple may emphasize different aspects of intercourse on different occasions, being playful during one episode of intercourse (recreational), experiencing deep emotional connection on another occasion (relational), and later, after discontinuing contraception, seeking to achieve pregnancy (reproductive, or more likely reproductive and relational).
Sexual acts, other than as a means of reproduction, are varied: Oral sex consists of all the sexual activities that involve the use of the mouth, tongue, and possibly throat to stimulate genitalia. It is sometimes performed to the exclusion of all other forms of sexual activity. Oral sex may include the ingestion or absorption of semen or vaginal fluids. Other non-penetrative sex acts are also common. While there are many sexual acts involving the anus, anal cavity, sphincter valve and/or rectum, the most common meaning of anal sex is the insertion of a man's penis into another person's rectum.
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Sexual ethics and legality
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Unlike some other sexual activities, vaginal intercourse has rarely been made taboo on religious grounds or by government authorities, as procreation is inherently essential to the continuation to the species or of any particular genetic line, which is considered to be a positive factor, and indeed, enables most societies to continue in the first place. Many of the cultures that had prohibited sexual intercourse entirely no longer exist; an exception is the Shakers, a group that reached a size of about 6,000 full members in 1840, but as of 2009 had only three members left. There are, however, many communities within cultures whose members refrain from any form of sex, especially members of religious orders and the priesthood in the Roman Catholic Church and Mahayana Buddhist monks. Within some ideologies, coitus has been considered the only "acceptable" sexual activity. Relatively strict designations of "appropriate" and "inappropriate" sexual behavior have been defined by human cultures for thousands of years. These legal or cultural restrictions may include:
- Sex among partners who are not married (this is sometimes referred to as fornication)
- Sex between a married person and someone to whom they are not married (called adultery or extramarital sex).
- Sex between partners of the same sex (also called homosexuality).
- Commercial sex (also called prostitution).
- Sex between a living human and a human corpse (also called necrophilia).
- Sex between close relatives (also called incest).
- Adults having sex with children (depending on the country and its laws, also called child sexual abuse)
- Humans having sex with non-human animals (also called bestiality).
- Sex between members of different tribes, ethnic groups, or races, as in South Africa or the United States during periods of racial segregation (also called miscegenation).
- Sexual intercourse during a woman's menstrual period, as seen in Judaism.
- Sex acts other than vaginal intercourse (including oral sex or anal sex, both sometimes called Sodomy).
- Sex, or pre-sexual behavior or communication inviting sex, in a public place (also called public indecency, or lewd and lascivious behavior).
- Depictions of sex in print or video (also called pornography).
- Touching a woman illicitly (also called "outraging the modesty of a female").
- Sexual intercourse that is terminated by the man before ejaculation, or results in ejaculation outside the vagina, as seen in ancient Judaism (also called coitus interruptus, or Onanism).
- Sexual touching of one's self (also called masturbation, or Onanism).
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 their will, or without their informed legal consent, is referred to as rape, and is considered a serious crime in most countries. Some countries codify as rape any sex with mentally handicapped persons of any age. Sex, regardless of consent, with a person under the age of consent is often considered to be sexual assault or statutory rape. The age of consent varies from country to country and often by state or region; commonly, the age of consent is set anywhere between twelve and eighteen years of age, with sixteen years being the most common age the law sets. Sometimes, the age of consent is lowered for people near the same age wishing to participate in intercourse. For example, in Canada, the minimum age of consent for all couples is 16. However, the age of consent can go below 16 on the condition that the couple still are not two years of age apart. Religions may also set differing ages for consent, with Islam setting the age at puberty, which can vary from around 10 to 14. There are often further restrictions on age concerning anal sex, homosexual sex, or sex with someone in a position of trust or authority, such as a teacher or caretaker.
Though there are exceptions, most non-Islamic and multi-cultural countries no longer criminalize consensual sex of any sort among adults. In contrast, Islamic countries typically imprison or execute homosexuals. Iran alone is estimated to have executed 4,000 persons for homosexual sex since the Islamic Revolution of 1979, including two teenage boys in 2005.
Religious and philosophical views
Modern humans, who date from approximately 400,000 years ago, have always reproduced by sexual intercourse. Modern religions and philosophies, on the other hand, are all less than 10,000 years old, and it is impossible to determine if there were earlier religious or philosophical views on sexual intercourse. Some religious traditions, such as Christianity, hold that the first humans came into being by an act of God and not through human sexual intercourse. That is, after each pair of animals or humans were created, they began reproducing through sexual intercourse. Others, such as Mormonism, hold that there is a Heavenly Father and Mother whose actions resulted in earthly children.
Religious and philosophical viewpoints on sexual intercourse are varied. Some hold that person should engage in whatever sexual act they desire so long as it does not involve children, animals, or those who cannot or will not willingly consent to participate. Others hold that sexual intercourse is acceptable even with an unwilling partner, so long as the two are married (also known as "conjugal rights" or "marital rights").
Ancient Judaism allowed sexual relations between one male and more than one female (polygamy), and Islam still does. The Bible required that a brother have sexual intercourse with his brother's widowed, childless spouse so as to provide her children and forbade coitus interruptus in such cases. Modern Judaism views sex and reproduction as the holiest of human acts, the act through which one can imitate God, the Creator.
The medieval Christian Church condemned coitus outside marriage and placed strict limits on permissible practices within it. Penance of bread, water, and abstinence was imposed for exotic congress, the following being one example:
- Dorsal sex (woman on top): three years penance
- Lateral, seated, standing: 40 days
- Coitus retro (rear entry): 40 days
- Mutual masturbation: 30 days
- Inter-femural (ejaculation between the legs): 40 days
- Coitus in terga (anal sex): three years if committed with an adult; two years if with a boy; seven years for habitual offenders; and 10 years if with a cleric
Today there is wide variation of opinion and teaching about sexual intercourse within and between the three Abrahamic religions, with some communities limiting sexual activity strictly to intercourse and others making practically no pronouncements on sex at all. Islam views sex within marriage as something pleasurable, even a spiritual activity and a duty. Some Moslems hold that male martyrs for the Islamic faith will receive multiple virgin females as a reward in the afterlife. Christianity views sex in marriage as holy. It affirms that everything God created, including sex, is good.
Pope John Paul II saw the human body as the only one capable of making the invisible — the spiritual and the divine — visible. He taught that human beings were created to freely choose to give themselves, expressing this through the language of their bodies. For him, marital sexual love is a symbol of their total mutual self-donation, and further fosters it, and thus it has great beauty, is a form of worship and an experience of the sacred. Non marital sex (masturbation and fornication) and contraception falsify the language of the body, he says, because they use the body for selfish ends and treats embodied persons as things and objects.
Hinduism has varied views about sexuality, but Hindu society, in general, perceives both pre-marital and extramarital sex to be immoral and shameful, notwithstanding popular culture. The Kama Sutra is a well-known product of Hindu society that extols the benefits of sexual intercourse. Buddhist ethics, in its most common formulation, holds that one should neither be attached to nor crave sensual pleasure. Some Asian societies shaped by Buddhist traditions take a strong ethical stand on sexual behavior. In the Bahá'í faith, sexual relationships are permitted only between a husband and wife.
Unitarian Universalists and Neopagans, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults other than the vows that individuals may have taken voluntarily.
Objectivism, the philosophy espoused by Ayn Rand, like other similar movements including libertarianism holds that people should pursue the lifestyle that makes them happiest so long as others are not hurt.
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