Sexual intercourse

The missionary position of human sexual 

intercourse depicted by Édouard

-Henri Avril

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 they may be hermaphroditic, as is the case with snails. Over time, the definition expanded and may now include other penetrative sexual acts, such as penetration of non-sexual organs (oral intercourse, anal intercourse) or by non-sexual organs (fingering, etc.). For example, penetrative acts between same-sex individuals can also be regarded as sexual intercourse.

Sexual intercourse typically plays a powerful role in human bonding, often being used solely for pleasure and leading to stronger emotional bonds. Non-penetrative sex (oral sex may or may not be penetrative) and mutual masturbation have been referred to as "outercourse", as it contrasts "outer" with "inter" (though the "inter" in "intercourse" means between two beings rather than being inside or outside of the body), but may also be among the sexual acts contributing to human bonding and considered intercourse. Despite strict definitions of sex, in the context of sexual intimacy (such as ones relating to "technical virginity"), it can be taken to mean any mutual genital stimulation (i.e. all forms of intercourse and outercourse). As with most forms of sexual interaction, individuals are at risk for contracting sexually transmitted diseases, and thus safe sex practises are advised.

Modern Judaism, Christianity, and Islam view sexual intercourse between husband and wife as a spiritual and edifying action. 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. Buddhism's injunction to "refrain from sexual misconduct" finds its interpretation and practical definitions at the level of the individual. However, within each of these major religious traditions exists subgroups with varying stances on acceptable sexual practices, and some religious groups prohibit monks and nuns from engaging in sexual intercourse altogether.

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. Like humans engaging in sex primarily for pleasure, this behavior in the above mentioned animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds.

Practices of human relations

Bonding and affection

Human sexual behavior and Human sexuality

In animals, sexual intercourse ranges from a purely reproductive activity to one of emotional bonding between mated pairs. It typically plays a powerful role in human bonding. In many societies, for example, 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.

In 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, dolphins, and chimpanzees 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 apparently 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.

The concept of "love" belongs to the domain of the virtues and to higher cognitive function, and is thus generally reserved for humans. When applied to animals, "love" is used largely for its colloquial meaning. In certain contexts, such as scientific research into emotional bonding, "love" is given a neuroscientific or neurochemical definition (rather than a human or a virtuous definition), and in such contexts human and animal intercourse are considered equivalent.

Reproduction and sexual practices

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. 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 (see sperm competition). 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.

Penetration by the hardened erect penis is additionally known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis"). 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. For females, stimulation of the clitoris plays a huge role in sexual intercourse; most can only achieve orgasm through clitoral stimulation.

Where a sperm donor has sexual intercourse with a woman who is not his partner, for the sole purpose of impregnating the woman, this practice may be known as natural insemination, or NI.

Sexual intercourse may also be defined as referring to other forms of insertive sexual behavior, such as oral sex and anal intercourse. 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, and may include the ingestion or absorption of semen or vaginal fluids. 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. Non-penetrative sex acts are also common. These acts are sometimes seen among heterosexuals as maintaining "technical virginity." Some gay men view frotting and oral sex as maintaining their virginity as well. The phrase to have sex can mean any or all of these behaviors (intercourse and outercourse).

Duration

Intercourse often ends when the man has ejaculated. Thus the woman might not have time to reach orgasm. In addition, many men suffer from premature ejaculation. Conversely, many women require a substantially longer duration of stimulation than men before reaching an orgasm.

According to a Kinsey study, just under half of men reported a time to ejaculation from intromission of five minutes or less.[citation needed] About a fifth claimed that coitus lasted 10 minutes or longer. Others may have taken over one hour.

A survey of Canadian and American sex therapists said that the average time for intromission was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.

Coitus difficulties

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.

Vaginismus is involuntary tensing of the pelvic floor musculature, making coitus distressing, painful, and sometimes impossible for women. It is a conditioned reflex of the pubococcygeus muscle, sometimes referred to as the "PC muscle". Vaginismus can be a vicious cycle for women, they expect to experience pain during intercourse, which then causes a muscle spasm, which leads to painful intercourse. Treatment of vaginismus often includes both psychological and behavioral techniques, including the use of vaginal dilators. A new medical treatment using Botox is in the testing phase. Some women also experience dyspareunia, a medical term for painful or uncomfortable intercourse, of unknown cause.

About 40% of males suffer from some form of 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 American Urological Association (AUA) estimates that premature ejaculation could affect 21 percent of men in the United States. 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.

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.

Health effects of human relations

Benefits

In humans, sex has been claimed to produce health benefits as varied as improved sense of smell, stress and blood pressure reduction, increased immunity, and decreased risk of prostate cancer; however, there is insufficient research to support these claims. 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.

Risks

In contrast to its benefits, sexual intercourse can also be a disease vector. There are 19 million new cases of sexually transmitted diseases (STD) every year in the U.S., and worldwide there are over 340 million STDs a year. More than half of all STDs occur in adolescents and young adults aged 15–24 years. At least one in four U.S. teenage girls has a sexually transmitted disease. In the US, about 30% of 15–17 year old adolescents have had sexual intercourse, but only about 80% of 15–19 year old adolescents report using condoms for their first sexual intercourse. More than 75% of young women age 18–25 years felt they were at low risk of acquiring an STD in one study.

Chlamydia is particularly dangerous because there are many infected individuals who experience no symptoms. Left untreated, chlamydia can lead to many complications, especially for women.

Hepatitis B can also be trasmitted through sexual contact. The disease is most common in China and other parts of Asia where 8–10% of the adult population is infected with Hepatitis About a third of the world's population, more than 2 billion people, have been infected with the hepatitis B virus.

Syphilis infection are on the rise in all parts of the United States and is related to about 21% of fetal and newborn deaths in sub-Saharan Africa. Syphilis causes genital sores that make it easier to transmit and contract HIV.

AIDS is caused by HIV which is spread primarily via sexual intercourse. The World Health Organization reported that in 2008, approximately 33.4 million people had HIV (about 2/3 in sub-Saharan Africa and 1.1 million in the United States ) , and 2 million died of AIDS worldwide.

Safe sex is a relevant harm reduction philosophy. Condoms are widely recommended for the prevention of STDs. According to reports by the National Institutes of Health (NIH) and World Health Organization, correct and consistent use of latex condoms reduces the risk of HIV/AIDS transmission by approximately 85%–99% relative to risk when unprotected.

Social effects

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).

Ethical, moral, and legal issues of human relations

Sexual ethics

Sex and religion

Erotic painting from India, 18th century

Erotic painting on ancient Greek kylix

While sexual intercourse is the natural mode of reproduction for the human species, we also have intricate moral and ethical guidelines which regulate the practice of sexual intercourse and that vary according to religious and governmental laws. These guidelines relate to the following areas:

Consent, age and mental capacity

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. More than 90% of rape victims are female, 99% of rapists male, and only about 5% of rapists are strangers to the victims.

Most 'developed' countries have age of consent laws specifying the minimum legal age a person may engage in sexual intercourse with substantially older persons, usually set at about 16–18, while the legal age of consent ranges from 12–20 years of age or is not a matter of law in other countries. Sex with a person under the age of consent, regardless of their stated consent, is often considered to be sexual assault or statutory rape depending on differences in ages of the participants.

Some countries codify rape as any sex with a person of diminished or insufficient mental capacity to give consent, regardless of age.

Marital status

Sexual intercourse is commonly considered a 'marital right' by many religions, permissible to married couples generally for the purpose of reproduction. Today there is wide variation in the opinions and teachings about sexual intercourse relative to marriage by the world's religions. Examples:

Christianity commonly views sex in marriage as holy and for the purpose of reproduction.

Islam views sex within marriage as something pleasurable, a spiritual activity, and a duty.

In Shi'ia Islam, men are allowed to enter into an unlimited number of temporary marriages, which are contracted to last for a period of minutes to multiple years and permit sexual intercourse. Shi'ia women are allowed to enter only one marriage at a time, whether temporary or permanent.

Pagans believe that the Charge of the Goddess instructs that "...all acts of love and pleasure are [the Goddess'] rituals and by the Wiccan Rede: "An it harm none, do as thou wilt", which is interpreted by many as allowing and endorsing responsible sexual relationships of all varieties.

Hinduism has varied views about sexuality, but Hindu society, in general, perceives extramarital sex to be immoral and shameful.

Buddhist ethics, in its most common formulation, holds that one should neither be attached to nor crave sensual pleasure.

In the Bahá'í faith, sexual relationships are permitted only between a husband and wife.

Unitarian Universalists, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults.

Shakers believe that sexual intercourse is the root of all sin and that all people should therefore be celibate, including married couples. Predictably, the original Shaker community that peaked at 6,000 full members in 1840 dwindled to three members by 2009.

Religious leadership

In some cases, the sexual intercourse between two people is seen as counter to religious law or doctrine. In many religious communities including the Roman Catholic Church and Mahayana Buddhists, religious leaders are expected to refrain from sexual intercourse in order to devote their full attention, energy, and loyalty to their religious duties.

Sexual orientation and gender

There is considerable legal variability regarding definitions of and the legality of sexual intercourse between persons of the same sex and/or gender. For example, in 2003 the New Hampshire Supreme Court ruled that female same-sex relations did not constitute sexual intercourse, based on a 1961 definition from Webster's Third New International Dictionary, in Blanchflower v. Blanchflower, and thereby an accused wife in a divorce case was found not guilty of adultery based on this technicality. Some countries, such as Islamic countries, consider homosexual behavior to be an offense punishable by imprisonment or execution.

Types

Some governments and religions also have strict designations of "appropriate" and "inappropriate" sexual behavior, which include restrictions on the types of sex acts which are permissible (see Sex and religion). A historically prohibited and/or regulated sex act is anal sex.

In other animals

 Animal sexuality

A pair of lions copulating in the Maasai Mara, Kenya

Mating houseflies

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.

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. 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 apparently 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.

(source:wikipedia)