Sexual intercourse is the act of inserting the erect penis of the male into the vagina of the female for reproduction and also for sexual enjoyment.
The terms "sexual intercourse" and "coitus" are used in reference to people. The term for the higher vertebrates (e.g. the lions shown here) and some other animals is "copulation". Many higher vertebrates animals (reptiles, birds. dogfish) reproduce internally, but their fertilization is cloacal. Other animals, such as catfish and most amphibians reproduce sexually but rely on external fertilization rather than copulation.
In a wider context, the term "sexual intercourse" may refer to a wider range of sexual activities than the act of coitus alone; see human sexual behavior for a discussion of this broader sense. This article focuses on heterosexual intercourse, wherein a penis enters the vagina.
Sexual intercourse is usually preceded by foreplay which leads to sexual arousal of the partners, resulting in erection of the penis and natural lubrication of the vagina. The erect penis is inserted into the vagina and one or both of the partners move back and forth to stimulate themselves and each other usually to the point of ejaculation and orgasm. A detailed description of the physiology of sexual arousal and orgasm can be found in the article Human sexual response cycle.
Main article: List of sex positions
Sexual intercourse may be performed in a wide variety of positions, the most common ones being:
- The woman lying on her back, the man on top and facing her ("missionary position")
- The woman on hands and knees, the man kneeling behind her ("doggy style" or in Latin coitus more ferarum "sex in the manner of beasts")
- The man on his back or sitting, the woman kneeling or squatting on top (slang "cowgirl" if the woman faces the man or "reverse cowgirl if the woman faces away from him)
- Both partners lying on their sides, the man entering from the front ("side-by-side position")
- Both partners lying on their sides, the man entering from behind ("spooning")
Biology of conception
Coitus is the basic reproductive method of Homo sapiens as of all mammals. During ejaculation, which normally accompanies the 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 thence into the fallopian tubes. 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.
Sexual intercourse should always be considered likely to result in pregnancy unless adequate contraceptive (birth control) measures are in force. Even then, pregnancy should be considered a possible outcome of the activity since no birth control measure is 100% effective. Coitus interruptus, or "withdrawal" of the penis from the vagina just before the man’s orgasm, cannot be considered an effective method of contraception and is not recommended. Abstinence from heterosexual sexual intercourse is the only 100% effective way to avoid pregnancy. Outercourse, in which there is sexual activity without insertion, can be performed without resulting in pregnancy provided that semen does not come in contact with the vulva.
Problems of intercourse
Many males suffer from erectile dysfunction, or impotence, at least occasionally. Some men also have dysfunction with orgasm in intercourse, called anorgasmia. Anorgasmia is much more common in women, however, and usually needs attention from both partners over a long time span to solve. Many women, especially younger women and women with relatively little sexual experience, experience difficulty achieving orgasm or may be unable to achieve orgasm. 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.
Sexually transmitted diseases
Main article: sexually transmitted diseases
Sexual intercourse, like other sexual activities that involve the possibility of transfer of body fluids, is also a means of propagating sexually transmitted diseases. Health care professionals suggest that condoms should be used to lessen the risk of contracting STDs, but they should by no means be considered an absolute safeguard. The best suggestion is to avoid sexual intercourse with anyone known to have a sexually transmissible disease, and, indeed, with anyone whose disease-negative status is in doubt.
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 itself 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 which has very few adherents. 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 are married, but not to each other (called adultery), against sexual intercourse with a close relative (called incest), and against intercourse during a woman’s menstrual period.
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 called rape and is considered a serious crime in most cultures.
The English-language profanity fuck literally means copulate but is also used in several other senses.
There is an urban legend that dolphins, bonobos, and humans are the only animals that have sex for pleasure; in actual fact, what distinguishes these three species from other animals is that they also have heterosexual sex when the female is not at a point in her gestation cycle suitable for successful impregnation , also, at least in the case of humans and bonobos, sexual intercourse can be engaged in for many reasons other than reproduction or other biological drive.
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.