The penis is the male reproductive organ in mammals and other species, including some birds and reptiles, and serves as the external organ in the male urinary tract. The urethra enables those primary functions by excreting both semen and urine. At most times the penis is flaccid, but when the male is aroused, it becomes enlarged and firm. Because the penis visibly identifies a person's sex as male, it has been credited with powerful social and psychological roles: "Sometimes the very possession of a penis conflates with all aspects of masculine identity" (Sims 2003, p. 245). In light of the involuntary nature of male arousal, this physical change has led the penis to be perceived at times as a powerful force of nature and at other times as emblematic of the bestial or, in theological terminology, sinful aspects of humankind (Friedman 2001).
The penis is composed of three pillars: two corpora cavernosa that lie next to each other on the upper or dorsal side of the penis and one corpus spongiosum, which is on the underside, or ventral side, of the penis. These tissues retain arterial blood during sexual arousal and cause the penis to become erect. Although penis size varies greatly in the flaccid state, in 80 percent of men the erect penis measures between five and seven inches, and most erect penises are close to six inches long or slightly longer (Sims 2003).
At the end of the penis is the glans penis, a bulbous tissue attached to the corpus spongiosum. A loose foreskin, or prepuce, covers the tip of the penis in its flaccid state, and this elastic skin is drawn back during an erection to expose the glans. The glans has a high concentration of nerves, some of which are unique to the glans and increase sensitivity to tactile stimulation. The lip of the glans, the corona, also contains a high concentration of nerve endings. The urethra, a tube for the excretion of fluids, traverses the underside of the penis to the meatus, an opening at the tip of the glans. This tube both drains the urinary bladder and ejaculates semen, a thick milky fluid composed of sperm and seminal fluid.
At the base of the penis is the scrotum, an external sac containing two testes, or testicles. Because of their external position, the temperature of the scrotum and testes averages 3 to 4 degrees Celsius lower than human body temperature; this is necessary for the production of healthy sperm. Immature sperm begin their development in the seminiferous tubules of the testes and migrate into the epididymis, a coiled tube on the top back side of each testicle. Sperm mature as they travel through the epididymis, a process that can take up to six weeks, although hundreds of million sperm can be produced each day. The vas deferens is the muscular tube through which the sperm enter the body, and the sperm are held in the ampulla, a region of the vas near the prostate gland, until they are ejaculated with seminal fluid through the urethra.
Penile erection is caused by the dilation of the arteries that bring blood into the penis. As additional arterial blood enters the penis, the cavernous and spongy tissues begin to swell and constrict the blood vessels through which venous blood circulates out of the penis. More blood enters the penis when the arterial veins are dilated (as a result of hormones released during sexual stimulation) than can return to the circulatory system, causing the spongy tissues to engorge and resulting in an erection.
Penile erections are necessary for reproduction. Rigidity during an erection facilitates the penetration of the penis into the vagina so that sperm can be deposited in the female reproductive tract, where they fertilize the egg. In preparation for ejaculation, the testes increase in size and press against the pelvis. Rhythmic muscular contractions during intercourse force sperm into the urethra, where they mix with seminal fluid from the seminal vessels and prostrate gland. Contractions in the urethra lead to the ejaculation of about one teaspoon of semen containing between 1 million and 600 million sperm during the male orgasm (Paley 1999).
Circumcision is a surgical procedure in which the foreskin is removed from the penis, permanently exposing the glans penis. Circumcision has been practiced in cultures around the world for thousands of years. Frequently this procedure serves a ritual or religious function; for example, circumcision is required in Judaism as a mark of a man's covenant with God (Friedman 2001). During the twentieth century doctors in the United States often performed circumcisions for hygienic purposes (Langley and Cheraskin 1954). Opponents of the practice argue that circumcision reduces the intensity of the sensation experienced during sexual intercourse.
Penises also can be modified through augmentation procedures, including implant surgery, piercing, and stretching. Tribal groups in locations from Uganda to India have tied weights to penises, stretching them to reach a length of twelve to eighteen inches (Bordo 2002). In the Hellenic period and during the Holocaust some circumcised Jews stretched the skin covering the penile shaft to develop a pseudo-foreskin and disguise their religious identity (Friedman 2001). Two surgical procedures commonly are used for penile augmentation: The penis may be injected with fat molecules, or a layer of fat may be grafted to the penis to increase its girth. The surgical procedure for lengthening the penis involves cutting the suspensory ligament so that the flaccid penis stretches farther from the body. At least 10,000 men have undergone augmentation surgery to lengthen their penises in the United States since 1990, but statistically valid studies of surgical success rates are not available. The penis also may be modified to increase sexual pleasure by inserting rings, bars, or pins. The penis most commonly is pierced through the glans or the underside of the penile shaft.
HISTORICAL AND CULTURAL PERSPECTIVES
A distinction must be made between the physical penis, the male organ of reproduction, and the phallus, the erect organ that symbolizes masculine power. Sam Keen hypothesizes that the exaggerated emphasis on the enlarged phallus provides "compensation for our feelings that the penis, and therefore the self, is small, unreliable, and shamefully out of control" (Keen 1991, p. 70). In European society social, religious, and biological associations have led to the abjection of the penis. Biological function and material presence characterize the penis, whereas the phallus is a symbolic attribute that allows its possessor to generate meaning and assert authority (Thomas 1996). Abstract representations of the erect penis that suggest its powerful phallic double may be generated unintentionally (Bordo 1999).
The penis has evoked extraordinarily strong reactions that differ across historical periods and cultures. Conservative societies sometimes resisted viewing, speaking of, or even acknowledging the penis: The extreme corporeal modesty associated with the Victorian period is an example of that attitude. During other historical periods and among other cultures public displays of the penis or a substitute have been acceptable and even fashionable. In ancient and Hellenic Greece men exercised without clothing at gymnasiums, and depictions of heterosexual courtship rituals suggest that men routinely exposed their penises to women they desired (Friedman 2001). Colorful codpieces (clothing worn over the male genitalia that sometimes was padded and sculpted) worn in Europe during the fifteenth and sixteenth centuries simultaneously concealed and accentuated the penis.
The significance of the penis as visible evidence of masculinity may lead to anxiety among men. Susan Bordo parallels men's insecurity about penis size with women's concern about body size. Just as average women perceive themselves as too large, the social importance and pornographic images of large penises generate impossible standards of comparison for the average human penis (Bordo 2002). The difference between the length of the penis in its flaccid state and that in its erect state may compound the social anxiety experienced by many men. Even the word for failing to achieve an erection, impotency, links the penis with masculine power or its absence. The prominence of Viagra since its production began in 1998 demonstrates the cultural value placed on achieving and sustaining an impressive erection. Through pharmaceutical advances, marketers suggest, the penis can be made reliable and men can become more powerful.
THEORIES OF RACE AND GENDER
Just as claims about greater intelligence, productivity, beauty, and other desirable characteristics have been used to mark the differences between social and ethnic groups, penis size has been used as evidence of superiority or inferiority. Despite the relatively consistent size of the human penis regardless of race, depictions of and jokes about stereotypical penis size have been used to assert ethnic difference. In ancient Greece foreigners, slaves, and barbarians were characterized as having large penises, whereas depictions of Greek men display small, thin penises (Friedman 2001). During the hearings for the confirmation of Supreme Court Justice Clarence Thomas in the U.S. Senate questions were asked to invoke the stereotype that black men have large penises, which may be used to imply an uncivilized sexuality. In contrast, the masculinity of Asian men often is ridiculed by assertions of small penis size.
Key aspects of Sigmund Freud's psychoanalytic theory link the penis with masculine and feminine development. As a result of threats or of viewing female genitalia, boys experience castration anxiety: the fear that the penis will be removed. This fear leads to the dissolution of the Oedipus complex and the development of normative masculinity (Freud 1989a). In contrast, the female child desires a penis after glimpsing a playmate's penis. Penis envy leads her to feel contempt for her own sex and to change the object of her desire from the penis to a male lover and a baby (Freud 1989b). In addition to its psychoanalytic meaning, the term penis envy is used commonly to describe a woman's desire for masculine privileges or authority.
Bordo, Susan. 1999. The Male Body: A New Look at Men in Public and in Private. New York: Farrar, Straus and Giroux.
Bordo, Susan. 2002. "Does Size Matter?" In Revealing Male Bodies, ed. Nancy Tuana, William Cowling, Maurice Hamington, et al. Bloomington: Indiana University Press.
Freud, Sigmund. 1989a. "The Dissolution of the Oedipus Complex." In The Freud Reader, ed. Peter Gay. New York: W. W. Norton. (Orig. pub. 1924.)
Freud, Sigmund. 1989b. "Some Psychical Consequences of the Anatomical Distinctions between the Sexes." In The Freud Reader, ed. Peter Gay. New York: W. W. Norton. (Orig. pub. 1925.)
Friedman, David M. 2001. A Mind of Its Own: A Cultural History of the Penis. New York: Free Press.
Hafez, Elsayed S. E., with B. Hafez and Sayed Dean Havez. 2004. An Atlas of Reproductive Physiology in Men. Boca Raton, FL: Parthenon.
Keen, Sam. 1991. Fire in the Belly: On Being a Man. New York: Bantam.
Knapp, Loren. 1998. Perspectives in Human Biology. Belmont, CA: Wadsworth.
Langley, L. L., and E. Cheraskin. 1954. The Physiology of Man. New York: McGraw-Hill.
Paley, Maggie. 1999. The Book of the Penis. New York: Grove Press.
Sims, Michael. 2003. Adam's Navel: A Natural and Cultural History of the Human Form. New York: Viking.
Thomas, Calvin. 1996. Male Matters: Masculinity, Anxiety, and the Male Body on the Line. Urbana: University of Illinois Press.
Jessika L. Thomas