Sexual intercourse

• 1. Defining The Act

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  In 1892, painter Édouard-Henri Avril captured a scene of penile-vaginal penetration titled The Missionary Position. This artwork reflects how the term coitus derives from the Latin word coire, meaning to go together or join. Most dictionary sources define sexual intercourse as the insertion of an erect male penis inside a female vagina followed by thrusting motions for pleasure or reproduction. Scholars Richard M. Lerner and Laurence Steinberg note that researchers rarely disclose how they conceptualize sex in their studies. They attribute this focus on penile-vaginal sex to the larger culture's preoccupation with this form of activity. Some definitions include anal sex, oral sex, fingering, or use of dildos and vibrators. Non-penetrative activities are sometimes labeled outercourse but may still be considered sexual intercourse by some people. The World Health Organization states that non-English languages use different words for sexual activity with slightly different meanings. Vulgarisms like fuck, screw, shag, and phrases such as sleep together appear across cultures. Laws in some countries use the euphemism carnal knowledge to describe these acts.

• 2. Biological Mechanics

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  During coitus, partners orient their hips so the penis moves back and forth in the vagina to cause friction without fully removing it. For human females, stimulation of the clitoris plays a significant role in sexual activity. Between 70% and 80% of women require direct clitoral stimulation to achieve orgasm. Indirect clitoral stimulation via vaginal intercourse may also be sufficient for some. Couples may engage in the woman on top position or the coital alignment technique to maximize clitoral stimulation. In non-primate animals, females copulate only when in estrus, the most fertile period of time in the female reproductive cycle. Bonobos, dolphins, and chimpanzees engage in sexual intercourse regardless of whether the female is in estrus. They also engage in sex acts with same-sex partners. This behavior in these animals is presumed to be for pleasure and contributes to strengthening social bonds. Natural human reproduction involves penile-vaginal penetration during which semen containing sperm cells is ejaculated into the vagina. The sperm passes through the vaginal vault, cervix, uterus, and fallopian tubes. Millions of sperm are ejaculated to increase chances of fertilization but only one is needed to fertilize an egg. Pregnancy begins after the fertilized ovum implants in the lining of the uterus called the endometrium.

• 3. Health And Risks

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  In 2010, the National Survey of Sexual Health and Behavior reported that one out of four acts of vaginal intercourse were condom-protected in the United States. Correct and consistent use of latex condoms reduces the risk of HIV/AIDS transmission by approximately 85% to 99%. There are 19 million new cases of sexually transmitted infections every year in the U.S. In 2005, the World Health Organization estimated that 448 million people aged 15 to 49 were infected per year with curable STIs such as syphilis, gonorrhea, and chlamydia. Some STIs can cause a genital ulcer and increase the risk of acquiring or passing on HIV up to ten-fold. Globally about 257 million chronic carriers of hepatitis B exist. In 2010, approximately 30 million people died because of HIV since the beginning of the epidemic. Of 2.7 million new HIV infections worldwide in 2010, 1.9 million occurred in Africa. The WHO stated that 1.2 million Africans who died of HIV-related illnesses in 2010 comprised 69% of the global total of 1.8 million deaths attributable to the epidemic. Approximately 123 million women become pregnant worldwide each year according to 2005 estimates. Around 87 million of those pregnancies or 70.7% are unintentional. About 46 million pregnancies end in induced abortion annually.

• 4. Social Dynamics

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  In 2012, the Federal Bureau of Investigation changed its definition of rape from carnal knowledge of a female forcibly against her will to penetration no matter how slight of the vagina or anus with any body part or object without consent. Most countries have age of consent laws setting minimum legal ages usually at 16 to 18 years ranging from 12 to 20. Sex with a person under the age of consent regardless of stated consent is often considered statutory rape. More than 90% of rape victims are female and 99% of rapists male. Only about 5% of rapists are strangers to the victims. Prior to the 1970s, rape definitions often included only penile-vaginal sexual intercourse. In some instances, penetration is not required for the act to be categorized as rape. In most societies around the world incest exists and is criminalized even if all parties are consensual. Laws prohibit all kinds of sexual activity between relatives including grandparents parents children siblings aunts and uncles. Zoophilia involving sexual activity between human and non-human animals is illegal in many jurisdictions under animal abuse laws. Until late 20th century there was usually a marital exemption in rape laws precluding prosecution of husbands for forced sex with wives.

  In the Roman Catholic Church if spouses engage

• 5. Legal Frameworks

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  in intercourse after matrimonial celebration it consummates the marriage otherwise it remains ratum sed non consummatum and can be dissolved by the pope. The Shakers believed sexual intercourse was root of all sin and all people should be celibate including married couples. Their community peaked at 6,000 full members in 1840 but dwindled to three members by 2009. In Judaism a married Jewish man must provide his wife with sexual pleasure called onah which is one condition he takes upon himself during the ketubah wedding contract. Islam views sex within marriage as pleasurable spiritual activity and duty. Shia Islam allows men to marry up to four wives simultaneously. Hinduism considers sex normal and necessary for fulfilling life according to Kama Sutra. Buddhist ethics hold that one should neither be attached to nor crave sensual pleasure since it binds one to cycle of birth and death samsara preventing attainment of Nirvana. Monastics undertake training rule of total abstinence from sexual intercourse. Lay people follow Five Precepts third of which avoids sexual misconduct involving causing suffering through behavior like adultery going with wife of another. Unitarian Universalists do not place boundaries on occurrence of sexual intercourse among consenting adults.