sexual intercourse

Vaginal sexual intercourse, also called coitus, is the human form of copulation. While its primary evolutionary purpose is the reproduction and continued survival of the human species, it often is performed exclusively for pleasure.
Sexual intercourse is also defined as referring to any form of insertive sexual behavior, including oral sex, as well as anal intercourse. The phrase to have sex can mean any or all of these behaviors.
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.

Coition of a Hemisected Man and Woman (c. 1492, by Leonardo da Vinci) is an artist's interpretation of what happens inside the body during coitus.
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 highly pleasurable orgasm and ejaculation are achieved. Penetration by the hardened erect penis is also known as intromission, or by the Latin name immissio penis.
Contents[hide]
1 Sexual reproduction
2 Other forms of sexual intercourse
2.1 Oral sex
2.2 Anal sex
3 Functions of sex beyond reproduction
4 Coitus difficulties
5 Sexual ethics and legality
5.1 Religious views
6 See also
7 References
8 External links
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Sexual reproduction

The missionary position is a commonly used position for sexual intercourse in humans.
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 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. If female orgasm occurs during or after male ejaculation, the corresponding temporary reduction in the size of the vagina and the contractions of the uterus that occur can help the sperm to reach the fallopian tubes, though female orgasm is not necessary to achieve pregnancy. 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.
If both participants are fertile, vaginal intercourse is likely to result in pregnancy, unless reliable birth control measures are used.

Other forms of sexual intercourse

Oral sex
Main article: Oral sex
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 or may not include the ingestion or absorption of semen and/or vaginal fluids.

Anal sex
Main article: Anal sex
Anal sex or anal intercourse is a form of human sexual behavior. While there are many sexual acts involving the anus, anal cavity, sphincter valve and/or rectum, the specific meaning describes the insertion of a man's penis into another person's rectum.

Functions of sex beyond reproduction

The woman on top sex position is frequently combined with kissing, caressing and embracing.
Humans, bonobos[1] and dolphins[2] 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. (These three species, and others besides, are also known to engage in homosexual behaviors.[3])
In both humans and bonobos the female undergoes relatively concealed ovulation, so that males generally do not know whether she is fertile at any given moment. There is a functional advantage to sex anytime for social reasons rather than reproductive ones.[citation needed] There is often an emotional attachment between members.
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 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[citation needed] and others[citation needed] 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 peoples' 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 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).

Coitus difficulties
While well-suited for effective stimulation of the penis, coitus is much less effective at stimulating the clitoris, the seat of the female orgasm, because it is small and outside the vagina. Up to 70 percent of women[4] rarely or never achieve orgasm during coitus without simultaneous direct stimulation of the clitoris with the fingers or other implement. Most women do require such direct stimulation, and ignorance or disregard of this fact is seen as a common cause of female anorgasmia.
Anorgasmia is the lack of orgasm during otherwise pleasurable stimulation. It is much more common in women than men. The condition may be related to a psychological discomfort with or aversion to sexual pleasure, or to a basic lack of knowledge of what the woman finds physically pleasing and is likely to result in orgasm.[citation needed] A sense of shame, or the feeling that she "should" be able to climax can compound the problem, along with feelings of shame on the part of her partner, who may believe that he does not excite her sufficiently.[citation needed] Masturbation is a well supported method for a woman to explore her body and discover what feels good for her. The absence of a partner can remove the sense of performance anxiety and allow the woman to relax and enjoy. Good communication and patience are essential in helping an anorgasmic woman achieve orgasm. Whether a woman considers anorgasmia a problem or not is highly individual, though many women find it very frustrating.
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 (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.
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.

Sexual ethics and legality
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 sect of Christianity that has four adherents at current. There are, however, many communities within cultures that prohibit their members to engage in any form of sex, especially members of religious orders and the priesthood in the Roman Catholic Church and priests 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 in human culture for thundreds of years. These have included prohibitions against specific positions, but even more often against:
Coitus among partners who are not married (this is sometimes referred to as fornication)
Coitus where a married person has sex with someone they are not married to. (called adultery or extramarital sex)
Coitus with a close relative (called incest). This may also be called inbreeding in slang terms.
The desire to have sex with children (called pedophilia).
Coitus among partners of different species (called bestiality).
Some cultures and religions, such as Islam and Judaism, prohibit coitus during a woman's menstrual period. This may be because a sacred text specifically forbids it. There is no medical reason for abstaining at this time.
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 many cultures around the world, including those found in Europe, northern and eastern Asia, and the Americas. 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 thirteen 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 14. However, the age of consent can go below 14 on the condition that the couple still aren't 2 years of age apart. There are exceptions in the case of anal sex or people in a position of trust/authority