sexology

Sex - Definition

What do we mean by "sex"?

Biological symbols for female and maleLeft: Female (Venus? Hand mirror? Vulva?) Right: Male (Mars? Bow and arrow? Penis and testicles?)

The word "sex" (from the Latin secare: to cut, to divide) originally refers to nothing more than the division of the human race into two groups: females and males. Every individual belongs to either one of these groups, i.e. to one of the two sexes. A person is either of female or male sex. However, upon closer inspection, the matter is not quite that simple. In some cases it can be extremely difficult to determine whether a particular individual is female or male. Sex - Factors in Determining a Person's Sex How can we determine whether a person is female or male? For an exact determination of sex one has to distinguish between at least seven factors, and each of these factors can have atypical exceptions: 1. Chromosomal sex 2. Gonadal sex 3. Hormonal sex 4. Internal accessory reproductive structures 5. External sex organs 6. Sex of assignment or rearing 7. Sexual Self-identification Sex - Factors in Determining a Person's Sex 1. Chromosomal Sex Typical:The cells of a female body contain a.o. two X chromosomes (XX). The cells of a male body one X and one Y chromosome (XY). Atypical:In rare cases, there are problematic exceptions, for example combinations like XXYor XYY or XXX. Individuals born with these exceptional chromosome combinations have various problems of physical development or are infertile. Sex - Factors in Determining a Person's Sex 2. Gonadal Sex Typical:The female body has ovaries (female gonads or sex glands). The male body has testicles (male gonads or sex glands). Atypical:In rare cases, ovarian and testicular tissue is found in the same body. Sex - Factors in Determining a Person's Sex 3. Hormonal Sex Typical:The gonads produce 'female' and 'male' hormones that play an important role in the development of the female or male body, especially before birth and during puberty, but also later in life. Atypical:Too much or too little of 'male' and 'female' sex hormones can have a decisive influence on the development and functioning of the body, and it can lead to an atypical physical appearance. Sex - Factors in Determining a Person's Sex 4. Internal accessory reproductive structures Typical:The female body has oviducts, a uterus, a vagina etc. The male body has sperm ducts, seminal vesicles, a prostate etc. Atypical:In rare cases, these organs are underdeveloped or missing. Sex - Factors in Determining a Person's Sex 5. External sex organs Typical:The female body has a clitoris, major (outer) lips and minor (inner) lips etc. The male body has a penis and a scrotum. Atypical:In rare cases, these organs are underdeveloped or missing. Sex - Factors in Determining a Person's Sex 6. Sex of assignment or rearing Typical:A child with a female body will usually be raised as a girl. A child with a male body will usually be raised as a boy. Atypical:It is possible to raise a female child as a boy and a male child as a girl. Indeed, this happens in very rare cases. Sex - Basic Aspects of Human Sexuality The 7 factors determining a person’s sex – in both their typical and atypical variations – are independent of each other. Therefore, in individual cases, there is a great number of possible combinations. Thus, in humans, "sex" turns out to be a complex phenomenon with biological, psychological, and social aspects. Even so, for a start, it is possible to distinguish three basic aspects:  - Sex,  - Gender, and  - Sexual Orientation. Sex - Basic Aspects of Human Sexuality The first basic aspect of human sexuality The factors 1-5: 1. chromosomal sex 2. gonadal sex 3. hormonal sex 4. the internal sex organs 5. the external sex organs can be summarized as a first basic aspect called biological or, more precisely,physical sex. In everyday language, it is often simply called sex. Sex - Basic Aspects of Human Sexuality The second basic aspects of human sexuality The factors 6-7: 6. sex of assignment and rearing 7. sexual self-identification can be summarized as a second basic aspect called psychosocial sex. It is also often called gender. It refers to the psychological and social role as either female or male which individuals play in society. Factor 6 – sex of assignment and rearing – means the gender role as it is seen from the outside, and factor 7 – sexual self-identification – means the role as it is experienced from the inside. Sex - Basic Aspects of Human Sexuality The third basic aspect of human sexuality There is still another basic aspect, namely the sexual interest in female or male bodies. Today, this is usually called sexual orientation. Sex - Basic Aspects of Human Sexuality Matters of Degree All three basic aspects of human sexuality, i.e. 1. sex,2. gender, and3. sexual orientation refer to differences of  d e g r e e . They should not be misunderstood as either/or propositions. This may be seen in the following tables. Sex - Basic Aspects of Human Sexuality A Spectrum of Variations When looking at the three basic aspects of human sexuality, we notice that, going from 1 to 3, the spectrum of possible variations widens, the size of the respective exceptions or minorities seems to increase: The number of exceptions is small under 1 (biological sex), because there are only few intersexes. It is somewhat larger under 2 (gender), because there are relatively more transvestites and transsexuals. The number is still larger under 3 (sexual orientation), because there are even more bisexuals and homosexuals.  Sex - Basic Aspects of Human Sexuality Sexual Variety The three basic aspects of sex are independent of each other and interact differently according to particular times, environments and situations. Thus, they shape each person’s individual sexual profile. This also includes his or her particular sexual interests or preferences. However, the latter are not necessarily permanent. They may change in the course of life, either spontaneously or as a result of positive or negative experiences, or as a result of therapy. On the other hand, certain aspects of sex are unchangeable (e.g. chromosomal sex) or can prove to be resistant to change (e.g. sexual self-identification and sexual orientation). Sex - Basic Aspects of Human SexualityA Practical Classification of Sexual Characteristics For the practical purposes of everyday life, one can distinguish between three kinds of sexual characteristics: 1. The primary sexual characteristics are the external sex organs. They are already present at birth and thus make it possible to determine whether a newborn child is a girl or a boy. 2. The secondary sexual characteristics are those physical features that develop during puberty and which further accentuate the anatomical difference between females and males. 3. The tertiary sexual characteristics are those psychological and social qualities that are nurtured in one sex and discouraged in the other (e.g. charm and sweetness in women, fighting spirit in men). The primary and secondary sexual characteristics are biologically determined, and they constitute a person's femaleness or maleness. The tertiary sexual characteristics are culturally determined, and they constitute a person's femininity or masculinity. The primary and secondary sexual characteristics refer to a person's femaleness or maleness (i.e. the physical character typical of one or the other sex); the tertiary characteristics refer to the person's femininity or masculinity (i.e. the psycho-social character typical of one or the other sex). The primary and secondary characteristics are biologically determined; the tertiary characteristics also have a bioligical basis, but are largely determined by cultural factors. Sex - Basic Aspects of Human Sexuality The Role of Chromosomes The sexual development of females and males is greatly influenced by theirchromosomes and hormones. The following sections describe this influence in detail. The Sex Organs - Definition What do we mean by sex organs? The expression "sex organs" has a double meaning: 1. The organs that determine a person's physical sex. They account for the greatest anatomical difference between the sexes. For this reason the sex organs are also called primary sexual characteristics. 2. The term also suggests that they are involved in a person's sexual response. Indeed, some people are under the false impression that the "sex organs" are the only organs so involved. However, the human sexual response is not restricted to a few particular organs but is a response of the whole body. Thus the mouth and the skin, for example, are also "sex" organs because they transmit and receive sexual stimulation. The Sex Organs - The Female Sex Organs  1. Mons Veneris  2. Major lip    (one of a pair)  3. Minor lip    (one of a pair)  4. Glans of the clitoris  5. Opening of urethra  6. Urinary bladder  7. Vaginal opening  8. Vagina  9. Cervix 10. Uterus 11. Fallopian tube      (one of a pair) 12. Ovary      (one of a pair) Schematic depiction of the female external and internal sex organs The Sex Organs - The Female Sex Organs The External Sex Organs Click on picture. The female external sex organs consist of the Mons Veneris, the major and minor lips, the glans of the clitoris, and the vaginal opening. All of these parts together are also often referred to collectively as the vulva(lat. covering). The Sex Organs - The Female Sex Organs The External Sex Organs The Mons VenerisThe Mons Veneris (lat.: mountain of Venus) consists of fatty tissue under the skin just over the pubic bone. On the outside, the area is covered with pubic hair, which first develops during puberty, and which makes the mons veneris by far the most conspicuous part of the vulva. The Major LipsThe major lips (lat. labia majora) are two thick and fatty folds of skin which extend from the mons Veneris downward, forming the outer borders of the vulva. On the outside, they are also covered with hair just as the mons Veneris. As the major lips usually lie close together, they seem to keep the other parts of the vulva covered. The Minor Lips Just beneath the major lips lie the minor lips (lat. labia minora). These are two thin folds of skin richly endowed with blood vessels and nerve endings. As a result, they are quite sensitive to the touch. The minor lips merge at the top forming a single fold of skin covering the glans of the clitoris. This fold is also called the foreskin or prepuce of the clitoris, or simply the clitoral hood. The Sex Organs - The Female Sex Organs The External Sex Organs The Clitoris The tip or glans of the clitoris (gr. kleitoris: little elevation) is located below the Mons Veneris at the point where the minor lips meet, forming a foreskin or prepuce. Externally visible under this foreskin is the glans of the clitoris. The body or shaft of the clitoris is a short cylindrical organ composed mainly of erectile tissue, i.e., of two spongy bodies (lat.corpora cavernosa) which can quickly fill with blood and thus cause the entire organ to stiffen and increase in size. Following it further inside, the clitoral shaft divides into two legs, each of which lies next to a bulb on either side of the vagina, and all of these structures swell under sexual stimulation. This is also true of spongy tissue surrounding the urethra. Interior view of the clitoris and surrounding erectile tissue The glansThe glans of the clitoris is partly covered by the clitoral hood or foreskin. It is possible for genital secretions (smegma) to accumulate under this foreskin, thus causing irritation and other problems. The glans is extremely sensitive to the touch as it is studded with innumerable nerve endings. Unlike the penis, however, the excited head of clitoris does not protrude but retracts under its hood. The clitoris is easily excitable by mechanical stimulation, and it plays an essential role in a woman's sexual excitement. A pleasure organThe average length of a clitoral shaft in its unexcited state is less than an inch and most of it is hidden from view. However, in the state of excitement it may swell to twice its usual diameter, and the rest of the tissue swells accordingly. This entire system of erectile tissue might correctly be called clitoral system or clitoris for short. This would also make the parallels to the penis much more obvious, even with regard to size. Furthermore, the clitoris is obviously the principal female pleasure organ, and it has no reproductive function. An internal organAll in all, the clitoris is more an internal than an external sex organ. It is listed here among the external organs only according to a now obsolete textbook tradition. The Sex Organs - The Female Sex Organs The External Sex Organs Click on picture The Vaginal Opening The vaginal opening lies below that of the urethra which, in females, is independent from the sex organs and is used exclusively for the release of urine. The urethral opening is very small, and it lies roughly halfway between the clitoris and the vaginal opening. By contrast, the vaginal opening is rather large, although it may be partially closed by a thin membrane calledthe hymen.   The Sex Organs - The Female Sex Organs The Internal Sex Organs Click on picture. The female internal sex organs consist of the ovaries, theFallopian tubes, the uterus, and the vagina. The Sex Organs - The Female Sex Organs The Internal Sex Organs: The Ovaries Location, form and functionThe ovaries (female sex glands or gonads) are two walnut-sized bodies which are located inside the abdomen on either side of the uterus. The ovaries serve a double function: 1. They produce eggs which are released into the Fallopian tubes. 2. They produce hormones which are secreted directly into the bloodstream. The Sex Organs - The Female Sex Organs The Internal Sex Organs The Fallopian Tubes Location, form and functionThe Fallopian tubes (named after the 16th century Italian anatomist Gabriele Fallopio) lead from the ovaries to the uterus. They are also sometimes called oviducts (lat.: paths of eggs), a term that accurately describes their function. They provide a passageway for the egg down to the area where it could implant in case of a fertilization. (They also provide a passageway for sperm cells swimming upward from the uterus trying to reach the egg). The wide ovarian end of a Fallopian tube has fingerlike extensions calledfimbriae (singular: fimbria) which move across the surface of the ovary; the uterine end leads directly into the inside of the uterus. The fertilization of an egg normally occurs in the upper part of a Fallopian tube. Inside the tube, there are innumerable hairlike growths called cilia (singular: cilium) whose movements, together with muscular contractions of the tubal wall, sweep the egg toward the uterus. (Inside the male vas deferens, the sperm cells are transported the same way since they are still unable to move by themselves at that point). The Sex Organs - The Female Sex Organs The Internal Sex Organs The Uterus Location, form and functionThe uterus (lat.: womb) is a muscular organ which is situated between and slightly below the ovaries, approximately in the center of the lower abdomen. The shape of the uterus, which is about 3 inches (ca. 7 cm) long, resembles that of a small pear turned upside down. The Fallopian tubes enter the uterus on either side near the top. The wide upper part, known as the body of the uterus, is usually tilted forward over the dome of the urinary bladder, and it is separated from the narrow lower part by a slight constriction. This lower part is called the cervix or neck of the uterus, and it ends in the deep portion of the vagina. The cervix contains a small opening through which sperm cells can travel from the vagina into the uterus. However, except for a certain period during ovulation, the cervical opening is plugged by an impenetrable mucus. The three layers of the uterine wallThe thick walls of the uterus are made up of three layers: 1. the external cover called the perimetrium, 2. the middle or muscular layer called the myometrium, and 3. the inner layer called the endometrium. This endometrium consists of special tissue which thickens every month as the uterus prepares for the possible implantation of a fertilized egg. If no implantation occurs, the endometrium deteriorates and is discharged through the cervix and the vagina during menstruation. The uterus during pregnancyIn case of a pregnancy, the uterus expands with the growing fetus. The extraordinary muscular structure of the myometrium not only allows for such vast expansion, but also provides the necessary pressure during labor when the fetus is finally expelled. The uterine muscles also contract during orgasm. The Sex Organs - The Female Sex Organs The Internal Sex Organs The Vagina Location, form and functionThe vagina (lat.: sheath) is a muscular tube about 3 1/2 inches long extending from the cervix to an external opening which is part of the vulva. The vagina serves three main functions: 1. It provides a passageway for the menstrual flow from the uterus to the outside. 2. It serves as a receptacle for a man's penis and his ejaculated sperm which      then may move on through the cervix. 3. It provides a passageway for the baby during birth from the uterus to the outside. The Sex Organs - The Female Sex Organs The Internal Sex Organs The Vagina The vaginal wallsUnder ordinary circumstances, the vagina is a collapsed tube, i.e., more a potential than actual space. Its inner surface, like that of the mouth, hosts different kinds of organisms which live in a healthy ecological balance. This balance can be upset, however, as a result of chemical interference. For this reason, vaginal sprays and douches should be avoided. The vagina cleanses itself with its own secretions. It also possesses a special protection against infection. The vaginal walls, which lie close together, contain mucous crypts and many blood vessels, but no glands and few nerve endings. During sexual excitement, these walls secrete a watery substance which serves as a lubricant during coitus. Without such lubrication, the insertion of a penis could be painful to both the woman and the man. The Sex Organs - The Female Sex Organs The Internal Sex Organs The Vagina The vagina during sexual intercourseThe vagina adjusts to the size of any inserted penis, large or small. However, that portion of the vagina which lies closest to the external opening may, in some cases, become too relaxed for the preference of either sexual partner. This can happen after childbirth, for instance, or simply as a result of the aging process. Conversely, it is also possible for the vaginal entry to become so tense and tight that it cannot be penetrated. Such a vaginal spasm is called vaginismus. Both problems can usually be solved by behavior therapy and/or appropriate exercises. Some of these exercises, the socalled Kegel exercises (named after the 20th century American gynecologist Arnold Kegel), can easily be performed by all women at all times, anywhere.   The Sex Organs - The Female Sex Organs The Internal Sex Organs The Vagina Ejaculation from the vagina?Some (by no means all!) women also expel some fluid from the urethra during orgasm. In the past, it was often assumed that the fluid could only be urine, and this caused the women some embarrassment. Sometimes another explanation was given: The fluid must have come from the vagina itself, perhaps as sudden excessive lubrication or as secretion from the Bartholin's glands. However, both explanations were wrong: The fluid did indeed come from the urethra, but it was not urine. Recent research suggests that the fluid is secreted by a system of urethral (or paraurethral) glands, i.e., glands which surround the urethra and open into it. This system of glands is more developed in some women than in others. In any case, it corresponds to the prostate in males, which also surrounds the urethra. Some researchers have therefore gone so far as to speak of a "female prostate." By the same token, the expulsion of fluid from this glandular system during orgasmic contractions has been called "female ejaculation," especially since the fluid itself has been shown to be similar to male prostatic fluid. (There are no sperm cells in these "female ejaculations", of course). The Sex Organs - The Female Sex Organs The Internal Sex Organs The Vagina The G-spotWhile only relatively few women "ejaculate" in this sense, many more have a certain sensitive spot, a cluster of tissue surrounding the urethra, which can be felt and stimulated through the anterior vaginal wall. This tissue (which is probably identical or at least connected with the system of urethral glands) first swells under intense stimulation and then contributes to a specially intense orgasmic release. Anatomically, this sensitive area has now become known as the "Gräfenberg spot" (G-spot) afterErnst Gräfenberg, a German-American gynecologist, who first described it in 1950. The Sex Organs - The Female Sex Organs Some Homologous Structures Some Homologous Structures in the Female and Male Sexual Systems Before a baby boy is born, the "male" hormone testosterone transforms his originally undifferentiated embryo, leading to the development of a male body with male sex organs. In case of a baby girl, the absence of testosterone at this stage lets the embryo grow "automatically" into a female body with female sex organs. However, since both male and female sex organs derive from the same embryonic cell mass, they still correspond to each other or, in scientific language, are "homologous." Female Ovaries Urethra Labia minora (minor lips) Labia majora (major lips) Clitoris Bartholin's glands Paraurethral glands ("female prostate") Male Testicles Prostatic urethra Urethral tube of penis Scrotum Penis Cowper's glands Prostate   The Sex Organs - The Female Sex Organs The Menstrual Cycle Click on picture What is the menstrual cycle?A woman becomes capable of reproduction during puberty and then loses this capacity in her early fifties. However, even in her fertile years she can conceive only during a certain time once a month when one of her ovaries releases an egg. The monthly recurrence of this event, together with other regular body changes, constitute the female reproductive cycle. Its most obvious external sign is menstruation (monthly bleeding). For this reason, the reproductive cycle may also be called menstrual cycle. Indeed, this latter term has the advantage of referring to a concrete experience which is familiar to practically all women, including those who do not reproduce. First and last menstruationA girl's first menstruation (gr.: menarche) usually occurs between the ages of 11 and 13. However, the second menstruation may very well be much farther away than just another month. During adolescence, menstrual cycles are rather irregular. It is only later that some definite pattern is established. In a mature woman, menstrual cycles usually last between 28 and 35 days. Still, some irregularity is always possible and quite normal. The irregularity increases again as the woman grows older. Finally, after menopause, her menstruations cease altogether. The Sex Organs - The Female Sex Organs The Menstrual Cycle: The Three Phases of the Menstrual Cycle I In scientific textbooks, the menstrual cycle is usually divided into two, three, four, or more different phases. For our present purposes, a division into three phases seems adequate. The Three Phases of the Menstrual Cycle(Seen as beginning after the last day of menstruation)   1. Preparing for Ovulation The endometrium begins to grow after menstruation. 2. Preparing for Implantation The endometrium is becoming ready for the implantation of a blastocyst. 3. Menstruation If no implantation occurs, the endometrium breaks down and is discharged in menstruation. The Sex Organs - The Female Sex Organs The Menstrual Cycle: The function of the menstrual cycle The basic function of the menstrual cycle is easily summarized: It prepares the lining of the uterus for the possible implantation of a fertilized egg. If no implantation occurs, the lining breaks down and is discharged through the vagina. This discharge is known as menstrual bleeding or simply menstruation. When the bleeding has stopped, the preparation of the uterine lining and thus the entire cycle starts again. Theoretically, a description of the mentrual cycle could begin with any of its phases. For the purposes of medical calculation, for example, the menstrual cycle is assumed to start with the first day of menstruation and to end with the last day before the next menstruation. However, in the present context it seems most useful to begin with the growth of the egg (ovum) and the gradual thickening of the uterine lining (endometrium). The Sex Organs - The Female Sex Organs The Menstrual Cycle: Description of the cycle For a better understanding, the following offers, in sequence, a detailed description of the three phases of the cycle: Preparing for Ovulation Preparing for Implantation Menstruation he Sex Organs - The Female Sex Organs The Menstrual Cycle: Description of the cycle Preparing for OvulationWhen the menstrual flow comes to a halt, the uterine lining is very thin. However, it slowly begins to thicken under the influence of estrogen, a hormone that is produced by the ovaries and released into the bloodstream. The rising estrogen level also stimulates the growth of some of the Graafian follicles that encase the immature ova. Eventually, only one of these follicles completes its growth, while the others recede. After approximately two weeks, on follicle ruptures and releases the ovum. This release is known as ovulation. At the time of ovulation, the uterine lining has thickened considerably and is close to becoming ready for a possible implantation. An ovulation occurs about 14 days before the beginning of the next menstruation. That is to say, if the ovum is not fertilized and implanted, the uterine lining will break down and will be discharged two weeks later. Thus, counting backward, in a menstrual cycle of 28 days, ovulation occurs on the 14th day; in a cycle of 35 days, it occurs on the 21st day. In other words, while the time period between ovulation and next menstruation is relatively constant, that between menstruation and next ovulation can vary considerably. Couples who practice the rhythm method of contraception have to keep this fact well in mind. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Description of the cycle Preparing for ImplantationShortly before ovulation, the follicle that encases the ovum begins to produce a new hormone called progesterone. This production increases dramatically after ovulation when the ruptured follicle is transformed into a "yellow body" (corpus luteum). In addition to progesterone, which plays an important part in the final preparation of the uterine lining, the yellow body also continues the production of estrogen. Under the influence of this hormonal stimulation, the lining of the uterus soon achieves its greatest thickness and receptivity for implantation. After its release from the ovary, the ovum enters the nearest Fallopian tube and begins traveling toward the uterus. Within a few hours, it undergoes its final maturation and becomes ready for fertilization. After its fertilization, the ovum develops into a cell cluster which continues its journey through the Fallopian tube to the uterus, where it arrives about three days later. Finally, after another three to four days, it begins to implant in the nourishing uterine lining, thus starting pregnancy. A pregnancy helps to sustain the yellow body and its production of estrogen and progesterone. As a result, no new ovulation occurs, and the uterine lining does not deteriorate. In other words, in case of a pregnancy, the menstrual cycle is suspended at this point and does not enter the third phase described here. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Description of the cycle MenstruationA fertilization is possible only within the first 24 hours after ovulation. If the ovum does not encounter any sperm cells during this time, it simply dies and disintegrates. Obviously, in this case there is no implantation either. As a result, the thick special lining of the uterus is not needed, but soon begins to break down and slough off. The waste material, consisting mainly of mucus, lining tissue, and variable amounts of blood, is discharged through the vagina. This discharge is known as the monthly bleeding or menstruation (from lat. mensis, month). It usually lasts between 3 and 5 days. In popular language, these days are also sometimes referred to simply as the "period." The first day of menstruation is usually considered the first day of the entire menstrual cycle. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Some practical issues There are some practical issues caused by the menstrual cycle: Discomfort during and before menstruation (PMS) Tampons and menstrual napkins Sexual Intercourse During Menstruation The Sex Organs - The Female Sex Organs The Menstrual Cycle: Some practical issues Discomfort during and before menstruation (PMS)During her "period," a woman may experience some physical discomfort, such as backaches, headaches, or cramps in the pelvic area. Indeed, some women develop these symptoms a few days before the menstruation begins. In this case, one speaks collectively of a “premenstrual syndrome” (PMS). Such menstrual discomforts can often be alleviated by adopting a healthy lifestyle, by physical exercise, and, in severe cases, by medication. In any case, there is rarely a need for an interruption of regular daily activities. For example, a menstruating woman can participate in sports without impairing her health in any way. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Some practical issues Left: Menstrual pads. Right: Tampons. Tampons and menstrual napkinsMost modern women wear tampons during their menstrual periods. These tampons are made of cotton or similar absorbent material, and they are introduced into the vagina where they absorb the menstrual flow. As long as they are replaced often enough, there is no medical objection to their use. In case of heavier menstrual bleeding, the traditional menstrual pads or napkins may be more appropriate. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Some practical issues Sexual Intercourse During MenstruationIn the past, many societies had strong prohibitions against sexual intercourse during menstruation. Generally, women were considered "unclean" during this time, and in some cultures there was a belief that sexual intercourse with a menstruating woman could make a man ill. However, modern medical research has exposed these and similar views as mere prejudices and superstitions. From a purely medical standpoint, there is no reason why sexual intercourse should not take place at any time during the menstrual cycle. In fact, many women are particularly responsive just before or during their periods. Still, some couples may hesitate to engage in coitus because of aesthetic objections to the bleeding. In this case, the use of a diaphragm should be considered. It will not only hold back the blood, but will also act as a means of contraception. After all, sperm cells can stay alive inside a woman's body for several days, and menstrual cycles can be quite irregular. An early ovulation can never be ruled out with complete certainty. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Menopause Usually between the ages of 45 and 50 a woman will notice that her menstrual cycles become more and more irregular until, eventually, she ceases to menstruate altogether. This permanent cessation of menstruation is called menopause. A broader term, climacteric (gr.: critical period), refers to the general physiological and psychological changes that occur during this time in a woman's life. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Menopause Menopausal symptomsAs described earlier, the number of a woman's oocytes dwindles to zero over the years. Correspondingly the woman also ceases to produce the hormones necessary for the preparation of the uterine lining. In some women, the resulting hormonal changes may, for a while, produce rather distressing symptoms, such as headaches, dizziness, fatigue, insomnia, and depression. Another symptom that may occur repeatedly is a "hot flash" or brief heat sensation spreading over the body. Such a flash may last from a second to a few minutes, and it may be followed by chills or heavy perspiration. These and other menopausal complaints can often be alleviated or even avoided by hormonal treatment. In most cases, the entire climacteric does not last longer than about two years. The Sex Organs - The Female Sex Organs The Menstrual Cycle: Menopause Gradual loss of fertilityAlthough menstruations become increasingly rare during this period, ovulations (and therefore conceptions) are still possible. A woman who does not want to become pregnant during her climacteric is therefore well advised to continue the use of contraception. After one year without menstruation, however, she can safely assume that she is no longer fertile. The loss of fertility does not affect a woman's sexual responsiveness. In fact, many women show a renewed and increased interest in sexual intercourse once they can stop worrying about unwanted pregnancies. The Sex Organs - The Female Sex Organs The Breasts Form and functionAlthough the rounded female breasts cannot be considered sex organs in the narrow sense of the term, they usually play an important part not only in erotic arousal, but also in the nurturing of the newborn. In a sense then, the breasts can be said to have some erotic as well as reproductive function. The breasts of a mature woman are two cushions of fat and tissue which surround her mammary glands. Whenever she gives birth to a child, these glands begin to secrete milk into special ducts leading to the nipples. The nipples, which are composed of smooth muscle fiber, and which contain many nerve endings, are very sensitive to the touch and can become erect during sexual excitement. The area around the nipples (areola) is pinkish, but becomes-and then remains-darker as a result of pregnancy. The female breasts begin to develop fully during puberty as a result of hormonal stimulation. Their eventual shape and size is determined by heredity. Left: Cross section of a female breast. Right: A: Nipples before the first pregnancy. (Areola is pinkish.) B: Nipples after the first pregnancy. (Areola is brownish.) The Sex Organs - The Female Sex Organs The Breasts Sexual significanceFor many men and women, the breasts have a special sexual significance. However, as in all sexual matters, preferences vary widely. In certain societies, long, pendular breasts are considered superior; in others, the taste runs to the round and firm. In some cultures, small breasts are praised as the most beautiful, while in others the ideal is an ample bosom. Even within one and the same culture, the concept of female beauty may change from one generation to the next, indeed from one individual to another. The Sex Organs - The Male Sex Organs Penis Corpus cavernosum (one of a pair) Corpus spongiosum Foreskin Glans Opening of urethra Scrotum Testicle  (one of a pair) Epididymis  (one of a pair) Vas deferens  (one of a pair) Seminal vesicle  (one of a pair) Urinary bladder Prostate gland Urethra Bulbourethral (Cowper's) gland  (one of a pair) Schematic depiction of the male external and internal sex organs The Sex Organs - The Male Sex Organs The External Sex Organs Circumcised adult penis. The male external sex organs consist of the penis and thescrotum. The testicles and their attachments, which are contained in the scrotum, are usually considered internal organs, although they are outside the abdominal cavity. The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis The penis (lat. tail) is a cylindrical organ which contains erectile tissue. To be more precise, there are three elongated spongy bodies inside the penis which extend through its entire length-two running parallel on top (the twocorpora cavernosa) and one running along the underside (the corpus spongiosum). This latter body contains theurethra (the duct through which urine and semen are released). Left: corpora cavernosaRight: corpus spongiosum The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis ErectionThe penis arteries can quickly fill the three spongy bodies with blood, thus causing them to stiffen. As a result, the penis becomes erect. Conversely, when the blood leaves the spongy tissue the erection subsides. Erections of the penis are usually triggered by sexual excitement, but they can also occur for other reasons. During an erection the penis increases in size. This is possible because the covering skin is very loose. The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis ForeskinToward the end of the penis some of this skin forms a freely hanging fold known as the foreskin or prepuce. This foreskin normally covers the tip or head of the penis called the glans. In the case of an erection, however, the glans protrudes from the foreskin and becomes fully exposed. The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis GlansThe glans is usually slightly thicker than the body of the penis, and its shape has been compared to that of an acorn (glans is Latin for acorn.) Actually it is the extension of thecorpus spongiosum, and it contains the external opening of the urethra. Since its smooth surface is studded with innumerable nerve endings, the glans is extremely sensitive to the touch, particularly around its rim. By the same token, it is also an important source of sexual pleasure for the male. The underside of the glans is attached to the foreskin by a thin tissue called frenum. Behind the rim of the glans and under the foreskin there are glands that secrete a cheeselike substance known as smegma. If the foreskin is tight this smegma may accumulate and cause irritation. In any case, good personal hygiene demands daily washing of the glans and removal of the smegma. For this the foreskin has to be pulled back. In some cultures, this problem does not arise because the foreskin is removed in a simple operation called circumcision. Left: Uncircumcised penisRight: Circumcised penis The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis CircumcisionTightness of foreskin (also called phimosis) is one of the reasons for a popular operation called circumcision. It consists of the surgical removal of the foreskin. This practice has a long tradition among Jews and Moslems, for whom it also has a religious significance. However, in the meantime circumcision has found wide general acceptance, and in the United States today most males are circumcised as a matter of course right after birth regardless of their religion. Circumcision has no effect on a man's sexual capacity. Circumcision for religious reasons (Left) Circumcision in ancient Egypt, ca. 3000 BC. (Right) Today: For Jews and Moslems, male circumcision also has a religious significance because it expresses Abraham's covenant with God. Shown here are tradidional Jewish circumcision instruments. Left: The barzel, a shield with a slit through which the foreskin is drawn before it is cut. Right: The izmel, a double-edged knife that can cut with either side.

The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis Penis sizeThe size of the penis is inherited just like that of other physical features (nose, ears etc.) The average length of a grown man's penis is between 3 and 4 inches when flaccid and between 5 and 7 inches when erect. However, there may be great variations in size from one individual to the next. Contrary to some widely accepted myths, the size of the penis is not related to a man's body build, skin color, or sexual prowess. A very short man may have a larger penis than a tall one (and vice versa), a white man may have a larger penis than a black man (and vice versa), and a man with a small penis may have more orgasms than a man with a large penis (and vice versa). Furthermore, some penises which greatly differ in size when they are flaccid may be of identical size when they are erect. The Sex Organs - The Male Sex Organs The External Sex Organs: The Penis Does penis size matter in sexual intercourse?Even a penis that remains relatively small during an erection serves every function of a larger penis. A woman's vagina, for instance, adjusts to any penis, no matter what its size, and since the vaginal walls contain few nerve endings, any difference in the woman's sensations depends on the firmness of her muscles surrounding the vaginal barrel as well as psychological factors. The latter is also true for sensations inside the rectum during anal intercourse. There is practically no feeling at all beyond the anal sphincter muscles. (This, incidentally, is the reason why some people who introduce long and hard objects into their rectum may seriously hurt themselves without realizing it.) The Sex Organs - The Male Sex Organs The External Sex Organs: The Scrotum The scrotum is a bag or pouch of skin which contains the testicles, and which hangs between the thighs at the base of the penis. The skin of the scrotum is comparatively dark and contains many sweat glands. Inside the scrotum there are two separate compartments, each of which contains one testicle and its spermatic cord which leads upward into the abdominal cavity. Part of this spermatic cord is a thin tube through which the sperm travels - the vas deferens. It is this vas deferens that is cut in a vasectomy. The spermatic cord also contains blood vessels, nerves, and muscles. In response to certain stimuli, especially cold temperatures, these muscles contract and pull the testicle closer to the abdomen. At the same time, the skin of the scrotum will also contract and appear thick and wrinkled. Ordinarily, however, the scrotum hangs loose, and its skin looks thin and smooth. In a way the scrotum acts like a thermostat, trying to provide an even temperature for the continuous production of sperm which is taking place inside the testicles. This temperature has to be slightly lower than that of the rest of the body.