Understanding sexuality

 | January 1, 2007

Understanding sexuality

At this stage in your life, you might feel that you know all there is to know about sex. After all, it's probably been many years since you had your first sexual experience. But if you're like a lot of people, you also possess spotty information and faulty beliefs, some of which may be preventing you from fully enjoying your maturing sexuality. To help you build a solid foundation for a fulfilling sex life, here's a quick overview of human sexuality basics.

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How do you define "sex"?

Vaginal intercourse is often given the lofty position as the ultimate sexual event, but clearly the story doesn't end there. Pleasurable activities — from casual intimacies such as kissing and caressing to more intense types of physical contact designed to produce orgasm — can complement intercourse or stand alone as a means for gratification. The penis and vagina are not the only tools for sexual enjoyment; people can give and receive intense pleasure without any direct genital-to-genital contact. The mouth, breasts, anal area, hands, and other sensitive spots on the skin are significant sources of erotic sensation. Even the friction of bodies rubbing together, clothed or unclothed, can bring sexual pleasure. Sexual activity does not always demand that you have a partner, either. Masturbation, viewing sexually stimulating materials, and creating fantasies all may be avenues for sexual gratification.

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Your sexual anatomy

You know these parts of your body are there, even if you don't know them by name. The following descriptions and the accompanying diagrams will acquaint you, part by part, with the structures that make up the male and female genitals.

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Female genitals

The appearance of a woman's genital organs is as individual as her face or body type. However, certain basic structures are common to all women (see Figure 1). The following parts make up the outer genitals, collectively called the vulva:

Mons pubis: The fatty mound of tissue that covers the pubic bone. Often called the "mons."

Outer lips (labia majora): The fleshy folds of skin, fat tissue, and smooth muscle that enclose the vaginal opening. Pubic hair, which may be plentiful or sparse depending on the individual, grows along the outer edges of the labia.

Inner lips (labia minora): A second set of thinner tissue folds, closer to the vaginal opening. Unlike the pubic hair–studded outer lips, the labia minora have a smooth surface and are rich in tiny blood vessels and nerve endings.

Clitoris: The most sensitive part of a woman's genital anatomy. This small mound of tissue is located at the point where the upper ends of the labia minora meet, above the vaginal opening. It's constructed from the same tissue as the head of a man's penis (the glans). A soft fold of tissue called the clitoral hood covers the pea-shaped protrusion.

Perineum: A stretch of hairless, sensitive skin that extends from the bottom of the vaginal opening back to the anus.

Unseen within a woman's body are these structures:

Vagina: A 3- to 5-inch tube of highly elastic tissue that extends from the vaginal opening to the cervix, at the base of the uterus. Just inside the entrance of the vagina is a ridge of muscles. Normally, the vaginal walls rest against one another. During childbirth, however, the vagina stretches wide enough to allow the baby to pass through. The vagina is lined with a layer of cells that secrete fluid to keep the inner surfaces moist. Blood vessels are plentiful within the vaginal walls, but most of the nerve endings are clustered in the outer third of the vagina.

Cervix: The knoblike tip of the uterus that forms the opening to the uterus from the vagina. Some women find pressure against the cervix enjoyable during intercourse.

Uterus: A muscular, fist-sized organ shaped like an upside-down pear. The primary job of the uterus is to harbor a growing fetus during pregnancy. Uterine muscles contract during orgasm, producing a pleasurable sensation.

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Male genitals

Compared with a woman's genitals, a man's sexual anatomy is a straightforward affair (see Figure 2). The primary structure is the penis. This organ does triple duty serving a man's sexual, reproductive, and urinary functions. The penis includes these structures:

Glans: The head of the penis. The urethral opening at the tip of the glans allows urine and semen to leave the penis.

Corona: The ridge that separates the glans from the shaft. This and the glans are the most sensitive portions of a man's penis.

Shaft: The main part of the penis. It houses the corpora cavernosa and the corpus spongiosum.

Corpora cavernosa (erectile bodies): Two flexible cylinders of erectile tissue that run the length of the penis to support erection.

Corpus spongiosum (spongy body): A cylindrical body of erectile tissue that surrounds the urethra and includes the glans.

Central artery: The vessel that supplies blood to erectile tissue in the corpora cavernosa.

Scrotum: The sac of skin at the base of the penis that holds the testes. The scrotum is covered, to varying degrees depending on the individual, with pubic hair.

Testes or testicles: The reproductive glands that produce sperm.

Urethra: A narrow tube that extends the length of the penis and carries both urine and semen out of the body.

Prostate gland: A walnut-sized gland located at the base of the bladder. The prostate produces a milky fluid that carries the sperm out of the body during ejaculation.

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The phases of sexual response

In the heat of sexual excitement, few people want to bother deciphering the dynamics of their sexual response. However, in cooler moments, acquainting yourself with the physiology of sex can offer clues to help you heighten your pleasure and improve your sexual capabilities.

The process that begins with the first glimmer of desire and culminates in the series of pleasurable rhythmic contractions we know as orgasm can be divided into four distinct phases. Each is characterized by a set of anatomic and physiologic changes. The four phases are as follows:

Desire. Also called lust or libido, desire is the wish for sex. A sight, sound, taste, touch, or smell may spark it. Or it may be ignited by a memory or fantasy. Desire occurs before any physical signs of sexual readiness take place in your body. Desire often leads to arousal and orgasm, but this isn't always the case. Arousal can also lead to desire, and desire can linger on its own indefinitely.

Arousal. During arousal, blood floods into the genitals, triggering the man's penis to stiffen and the woman's labia, clitoris, and upper vagina to swell. Moisture begins seeping from the vaginal lining, creating lubrication. The vagina lengthens, the uterus rises, and the inner and outer lips pull apart, exposing the vaginal opening. The man's testicles pull closer to his body, and his scrotum becomes thicker and flatter. In both sexes, breathing and heart rate accelerate, muscles throughout the body tense, the skin flushes, and nipples become erect.

Orgasm. When muscle tension and genital engorgement peak, a series of rhythmic contractions occurs in the sex organs. The contractions force the congested blood out of the tissues and back into circulation. Along with this comes an abrupt release of muscle tension and a pleasurable sensation. In a man, penile contractions expel semen out of the urethra; this is known as ejaculation. Some women also release fluid during orgasm. While this fluid comes out of the urethra, it's not urine. Glands located in the same area as the G-spot may produce the fluid.

Resolution. Following orgasm, heart rate and blood pressure gradually return to their normal levels. In a man, the penis becomes flaccid; in a woman, sex organs gradually return to their unaroused state. After orgasm, it takes some time before an individual can have another orgasm. For a woman, this stage may pass quickly, allowing her to have multiple orgasms in a short span of time if stimulation continues. A man generally needs to wait longer — from several minutes to hours or days, depending on his age — before he is able to ejaculate again.

While it's possible to identify these discrete parts of the sexual response cycle, not every sexual encounter needs to progress through all four phases in an orderly manner. Nor must the process necessarily include orgasm. This much is true for both women and men.

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Differences in male and female response

In the decades after William H. Masters and Virginia E. Johnson introduced the concept of the stages of sexual response in 1966, it was widely assumed that a woman's response closely mimicked that of a man. More recently, however, researchers have focused attention on women's sexual response. Rosemary Basson and her colleagues at the University of British Columbia have found that the patterns of response may vary widely between the sexes.

For example, when it comes to desire, male and female sexual responses diverge. The sex drive of men tends to be goal-oriented, setting its sights on intercourse and orgasm. This drive is propelled by frequent sexual fantasies and thoughts. Although women are equally capable of strong sexual urges, typically desire manifests itself as a more diffuse, sometimes elusive, drive. Women are more likely to become aroused by demonstrations of emotional intimacy — such as acts that reveal caring, commitment, or tenderness — rather than sexual fantasies alone.

This school of thought also contends that women may experience the stages of sexual response in a nonlinear manner. That is, arousal may need to occur before desire appears. In turn, the emotional intimacy that typically occurs between partners following lovemaking ("afterplay") can trigger a woman's desire for sex in the future. Women may also find that arousal and orgasm progress in the form of a series of rolling hills, rather than as a steady buildup to a dramatic peak followed by a steep drop.

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The impact of aging

Advancing years leave their mark on the body, mind, and emotions. Some of these changes are for the better, while others are less desirable. Sex is no exception. Many of the physical changes that come with age have noticeable effects on the sex organs and the sexual cycle (see Table 1). Thus, the careful lovemaking of a 70-something couple may bear little resemblance to the lusty pairings of 20-year-olds. This isn't necessarily a bad thing. Greater experience, fewer inhibitions, and a deeper understanding of your needs and those of your partner can more than compensate for the consequences of aging, such as slower arousal, softer erections, reduced vaginal lubrication, and less intense orgasms. And these physical changes can provide an impetus for developing a new and satisfying style of lovemaking — one that's based more on extended foreplay and less on intercourse and orgasm.

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The role of menopause

While midlife brings many changes for women, menopause is clearly a physical milestone. Menopause and the preceding months or years (known as perimenopause) are marked by hormonal fluctuations, which can provoke a host of symptoms from insomnia and irritability to dry skin and a thicker midriff (see Table 2). Many of these effects — vaginal changes and loss of libido, in particular — can wreak havoc on a woman's sex life.

Fortunately, women don't have to be at the mercy of their hormones. Vaginal lubricants, lifestyle changes, or hormone supplements may help alleviate many of these problems.

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Is there a male menopause?

The answer is both yes and no. In the strictest sense, men don't normally experience the precipitous drop in reproductive hormones that marks a woman's midlife. Although testosterone — the hormone responsible for a man's libido and fertility as well as his deep voice and facial hair — does taper off as a man ages, the process happens gradually. After about age 25, the level of testosterone in the blood diminishes by an average of 1% each year. But this fact means little in itself because actual levels can fluctuate dramatically from person to person. It's not impossible for a man in his 70s to be able to father a child.

That said, men may notice changes in their sex lives after they reach their 50s. Erections may require more direct stimulation, the need to ejaculate is less urgent, and the rest period between ejaculations grows longer. However, none of these effects need interfere with a satisfying sex life, provided the man and his partner understand these changes and integrate them into their lovemaking. A couple may find that less penile sensitivity means that the man may be able to enjoy a wider range of erotic sensations and maintain his erection longer. And his experience may pay off in improved sexual technique and a better understanding of what will please his partner.

An exception to the typical pattern of declining testosterone levels is a disorder called hypogonadism, which can strike at any age. In this condition, the testes don't produce enough testosterone to maintain normal male functions and characteristics. While it's clear that supplementing testosterone is an effective treatment for hypogonadism, it's not apparent whether men without hypogonadism benefit from artificially boosting testosterone to the levels of their youth. In addition, testosterone supplementation carries certain risks: It may promote prostate cancer and other prostate abnormalities, cardiovascular disease, and sleep problems.

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Aging and erectile dysfunction

Although erectile dysfunction becomes more common with age, it is not an inevitable part of growing older. It's true that over the years, testosterone levels decline, and often other changes occur: Penile tissue becomes less elastic, blood flow diminishes, and nerve communication slows. But these aren't the only possible causes of erectile dysfunction. Often, erectile problems stem from illnesses that become more prevalent with age or the medications used to treat these illnesses. Many of these conditions can be prevented with good health habits such as following a healthy diet, exercising regularly, maintaining normal weight, and not smoking.

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What is sexual dysfunction?

Sexual dysfunction can be defined as any aspect of your sexual response that causes you or your partner dissatisfaction or distress. The focus here is not on the problem itself, but on the fact that the condition is troubling to the people involved. For example, if both members of a couple are content to live without sexual activity, then such conditions as erectile dysfunction or vaginal dryness would not be considered sexual dysfunction. Likewise, a woman who is not involved in a relationship may not be concerned by her low libido. On the other hand, if she finds a partner who has a more active sex drive, her lack of interest may become a problem.

Experts usually divide types of sexual dysfunction into male and female issues. Under these headings, they define more specific problems based loosely on three of the four phases of sexual response: desire, arousal, and orgasm. Despite these distinctions, sexual problems are often complex and incorporate elements from more than one category.

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For women

Sexual desire disorder. The absence of sexual fantasies, thoughts, or behavior. Sexual aversion disorder, which is the avoidance of certain types of sexual activity because of anxiety, falls under this heading as well, although it has its roots in different psychological issues.

Sexual arousal disorder. The lack of sexual excitement, including absence of vaginal lubrication and other physical indications of arousal.

Orgasmic disorder. Difficulty or delay in reaching orgasm, or absence of orgasm after sufficient stimulation.

Sexual pain disorders. Genital pain during sexual intercourse (dyspareunia). This category includes nonspecific pain in the vulva (vulvodynia) and involuntary spasm of the vagina (vaginismus) that prevents penetration.

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For men

Sexual desire disorder. The absence of sexual fantasies, thoughts, or behavior. Although this problem is more common in women than in men, about one in seven men reported low libido in a survey published in the Journal of the American Medical Association in 1999. And this figure rises with age.

Erectile dysfunction. The inability to produce an erection that's sufficient for intercourse. Although this is a relatively uncommon problem for young men, about 44% of men ages 40–70 have partial or complete erectile dysfunction.

Ejaculatory disorders. These include several orgasmic disorders. Rapid or premature ejaculation occurs when the man ejaculates before penetration, immediately after penetration, or before the couple has achieved a mutually satisfying sexual experience. Delayed ejaculation, when a man has a normal erection but isn't able to reach orgasm, is less common, but tends to increase with age. Certain antidepressant medications, particularly selective serotonin reuptake inhibitors (SSRIs), can cause delayed ejaculation.

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Review Date: 2007-01-01

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