Unit 9-Reproductive Processes

Chapter 27


1. Introduction:

     After the beginnings of adolescence, both boys and girls begin to be interested in copulation, or coupling. This act involves the insertion of the erect penis into the vagina. A series of rhythmic movements, to be described below, eventually results in the discharge of seminal fluid containing sperm cells into the vagina and a series of vaginal contractions. Some of the sperm cells find their way into the body of the uterus, a few to the Fallopian tube, and fewer still to the ovum.

     Both sperm and egg are haploid cells, meaning they each contain half the normal number of chromosomes. The fusion of two haploid cells results in the formation of a diploid cell, which contains the normal number of chromosomes. This fusion is called fertilization and usually occurs in the Fallopian tube.

     There are extremely strong attitudes on copulation in most cultures. Copulatory behavior is, to a very large extent, determined by these attitudes. Marriage manuals, which purport to describe copulation and foreplay, usually describe the writer's culturally conditioned attitudes rather than the biological phenomenon, and generations of otherwise uninformed young people, guided by these manuals, tend to make the behavior described in them real.

     Animal studies have not proved very instructive. Outside of the primates, female receptivity, heat, is confined to rather short periods of time and determines when copulatory activity will occur. Primates seem to be quite shy about being watched and are, of course, unable to communicate many of the psychological events associated with copulation.

     Humans are also limited in their ability to communicate these events. This is partially a consequence of a culturally imposed prudishness, and partly it stems from an inadequacy of the language. This will be discussed again in Part 3 of this chapter.

     The most objective information regarding human copulation was published in a book called "Human Sexual Response" by Masters and Johnson, in 1966. Much of this chapter is based on information taken from this book.

2. The Sex Drive:

     The objective observer, free of prejudice, would note that exactly as many female animals copulate as males. Nevertheless, it is part of our culture to believe that male animals have a stronger sex drive than females. It is not clear why this belief exists, but it is almost certainly fallacious.

     It does seem clear that the sex drive begins in adolescence in both sexes and lasts throughout life. It is said that it is less in the old than in the young, even though this is not well established as a physiological fact.

     In laboratory animals, the sex drive is displayed as sexual behavior, almost as if the latter were instinctive. In humans, the drive appears to require instruction. Sexual relationships in man are extraordinarily complex, and reading, instruction by word of mouth, and imitation appear to replace "instinct". It is by no means unknown for human beings exposed to their first serious sexual contact to be at a total loss as to how to behave. The deficiency is usually remedied, but not always. The remedy may involve instruction, sometimes by the sexual partner, and it often involves trial and error, particularly when both partners are inexperienced or shy.

3. Foreplay:

     Copulation in Western culture is usually preceded by activities which though in themselves pleasurable, should be regarded primarily as a preamble to the insertion of the penis into the vagina. The nature and duration of these activities is extremely variable, perhaps more so than any other human activity.

     Endearing words and caresses may begin foreplay, but so may the visual perception of nakedness or the auditory perception of suggestive words. Non-genital contact is a common type of foreplay, varying from hand holding and kissing to manipulation of the breasts, thighs, or loins.

     In general, but not always, women prefer more early foreplay than men, but the type of foreplay preferred by any woman is conditioned by her training, educational background, and factors of the moment. This is as much as to say that women are variable, in this respect, not only from woman to woman, but also from time to time.

     Men are also variable, though to a smaller extent. Some men become bored by protracted foreplay; others may be put off by a woman to whom foreplay is of minor interest. Most men, however, respond from the beginning with penile erection, a process only partially understood.

     The penis is capable of being filled with extra blood. This is due to the fact that it contains blood vessels communicating directly with arteries but not usually filled with blood. They can, however, be filled with blood at arterial pressure on sexual stimulation. In experiments on dogs, it has been found that this is accompanied by venular dilatation rather than venular constriction. Thus, there is a great flow of blood at high pressure through the erectile tissue, as opposed to a small high pressure flow into erectile tissue from which the outlet is blocked. Comparable experiments on man are lacking. The structure of the erectile parts of the penis is shown in Figure 372.

     When inflated with blood, the penis becomes longer and thicker. Formerly pendulous, the erect penis goes upward and anteriorly, conforming to the structure of the inflated parts. These are shown in Figures 372 and 373. Specific nerves whose stimulation produces erection are known, called the erector nerves; they are classified as parasympathetic, and like the rest of the autonomic nervous system, they are under the control of higher centers. The skin of the erect penis, particularly its terminal end, called the glans, becomes the site of pleasurable sensation, though the non-erect penis normally gives rise to no sensation at all. It should be noted here that the pathways for this sensation are not known, and it is not even certain that the skin of the glans is most responsible for the pleasureable sensation. Figure 373 shows the erect penis.

     As foreplay continues, the dominant stimulus becomes touch--most of the touching is done by the male, using his hands; this touching stimulates the female.

     The idea that there are "erogenous zones", stimulated by touch, has some basis in fact, for they exist in both sexes and tend to be concentrated in the external genitalia. Outside of these, they are remarkably unpredictable, especially in women. As a general rule, the mouth is erogenous in both sexes, but there are exceptions, and the female breast, particularly the nipple (which is erectile) is usually erogenous, but again there are exceptions. The ear lobes are erogenous in some women, the medial surfaces of the thigh in others, and still others are stimulated through the skin of the neck. For some persons of either sex, only the external genitalia are erogenous.

     The genital areas are almost invariably erogenous. Stimulation of the female genitalia, usually by the male hand, heightens female excitement. The vaginal walls produce a watery secretion, and the clitoris, which contains erectile tissue, usually erects, and the whole genital area becomes engorged with blood. This condition, called tumescence, is also applied to the male erection, and is not entirely pleasant. The sensation may be compared to an itch and is associated with considerable excitement. It is generally believed that the clitoris is the most erogenous zone of the female genitalia, and though this may be true, the clitoris is by no means indispensable for sexual excitement. The clitoris is ritually removed in young girls in some cultures without any apparent effects on sexual behavior, and some women find manual stimulation of the clitoris painful.

     The genital areas of women are, as might be expected in a prudish culture, normally named in Latin or Greek, since hardly anyone understands these languages. The famous four letter words are only a little more helpful, since respectable dictionaries look the other way when they come up, and the public usage is lamentably imprecise. The use of classical languages is illustrated by the term pudenda, meaning those things one ought to be ashamed of, for the whole area--this term is also used for the male organs. Vulva, Latin for shield, is a synonym in the female. Labia majora means larger lips in Latin, the labia minora being the smaller lips within the labia majora. Both surround the Greek clitoris, the origin probably being from the Greek verb "to shut", though the structure shuts nothing. The vagina, a Latin word, is a sheath. An illustration may be more helpful (Figure 374).

     Perhaps the best English word for the sexually excitable area in women is the crotch, in particular its anterior parts. The vagina itself is not particularly sensitive to stimulation. The pleasurable sensations which are aroused from its penetration seem to be due in part to inadvertent stimulation of the clitoris and the rest of the external genitalia; a large part is probably due to the sense of intimacy and, in the case of experienced women, anticipation of the acts to come.

4. Copulation:

     The aroused woman usually grasps the erect penis and inserts its tip against the vaginal orifice. Once so placed, an appropriate movement of either partner results in maximum penetration of the vagina. The vaginal walls are usually lubricated by a watery secretion by this time; premature insertion, without lubrication, may be quite distressing to both partners. During the insertion, there is little stimulation of the female, though there is some as the labia minora rub against the shaft of the penis and are stretched a little, which in turn moves the clitoris to which they are attached. All these structures are erogenous, as has been noted.

     When penetration is maximal, the pubic areas of both partners are in contact. Female stimulation is derived from all the genital area. This includes the vaginal orifice, the labia minora, and the labia majora as well as the clitoris.

     It is by no means clear why the penis is withdrawn after maximum penetration. The act is clearly controlled by the voluntary muscles of both male and female, the greater movement in this culture being male. Despite the female pleasure in pubic contact the partners move apart until the tip of the penis comes to be just within the vaginal entry.

     Active penetration occurs again, and again withdrawal follows. Excitement increases in both male and female with each penetration and withdrawal; these become more and more frequent and penetration more and more forceful. It may be noted here that during excitement the clitoris, which may have been the first genital erogenous zone, becomes congested with blood. Muscles attached to it pull it out of the way so that it is no longer subject to stimulation. Female stimulation is now increased by touch receptors in the labia minora and at the vaginal entry; probably touch receptors in the labia majora add to the stimulation. The stimulation results in widespread changes. The nipples erect and the breasts swell. The labia minora become congested with blood, and by enlarging, lengthen the vaginal cavity. The outer third of the vagina contracts while its inner two thirds relax. Male stimulation is maintained and increased almost entirely by touch receptors in the penis. In both sexes, a constant level of excitement is finally reached, called the plateau.

     The duration of the plateau phase shows great variability; it is not always the same in the two sexes.

     The plateau phase in men may be as short as a few seconds, or it may last for several hours. Women may never reach a plateau phase, but on the other hand they may have several plateaus terminated by orgams, plateaus being reached again quickly through pudendal stimulation, while the male partner remains at plateau.

     Orgasm, the usual method of termination of the plateau in most men and some women, occurs as a result of unknown circumstances. Presumably, the stimuli of the plateau phase have a cumulative effect, but it is not at all clear where this accumulation occurs.

     Both male and female orgasms appear to be quite involuntary responses, involving both smooth and skeletal muscle. Though popular belief has it otherwise, orgasm in the female is much more intense that that of the male. More muscles are involved, somatic sensation is much more depressed, and the capacity for voluntary action is much more reduced in women than in men during orgasm.

     The relatively simple male orgasm involves the sudden ejection of seminal fluid into the prostatic urethra. The fluid, consisting of prostatic fluid, seminal vesicle fluid, and spermatozoa, is propelled by the contractions of the smooth muscles of the structures involved and also by the contractions of the striated muscles of the pelvic floor. The internal sphincter of the bladder closes so that seminal fluid goes forward. Within a few seconds, the increased blood flow which brought about erection is restored to normal and the erect penis shrinks, detumescence.

     The female orgasm is a little less commonly achieved but much more extensive. Skeletal muscles contract throughout the body, in particular those which grasp the partner, but the muscles of the face and neck are also involved. The vaginal muscles contract or relax violently and frequently, the contractions involving one third of the vagina, beginning at its outlet. These contractions occur about once a second and go on for a few seconds. Some believe that they act to keep seminal fluid at the entrance of the uterus (Figure 375). However, there is reason to suspect that insemination of the uterus is less likely when there is a female orgasm.

     A woman who achieves orgasm shows rapid reversal of the steps of the excitement stage. The breasts shrink, the clitoris returns to its normal position, the vaginal muscle relaxes, and labia minora is no longer congested and returns to normal size. These changes, like those in the male, can be considered detumescence. For a few moments, a woman who has achieved orgasm is quite unresponsive. Unlike most men, however, she is capable of almost immediate re-excitement, establishing a new plateau and having another orgasm. Indeed, multiple orgasms are possible.

     There is a widespread popular belief that there is some special advantage to simultaneity of male and female orgasms. The exact nature of the advantage has not been defined, so it is consequently difficult to determine if it exists. As noted earlier in this chapter, the vocabulary of sexual relationship is defective, and sexual matters are not usually the subject of informed conversation. It is an almost inevitable consequence of this that most people's sexual convictions are irrational and superstitious. The one just cited is an example, but there are many more.

     A woman whose partner achieves orgasm before she does does not show the rapid return to the resting condition characteristic of the male or female who has achieved orgasm. However, restoration does occur, usually well within an hour.

5. Varying Patterns of Copulatory Behavior:

     The preceding section described copulation in the mode accepted as normal by most persons in the United States and Europe. Of late, there has been wider recognition that other modes exist. Essentially, however, the same acts are involved, and the same responses occur. Interested students can find guides to these other modes in any marriage manual, in the works of creative writers, and in translated Oriental writings. Different modes have been recommended for different situations, though the reasoning given is sometimes unimpressive, and the credentials of most writers on the subject are not usually given. This should not be construed as a brief for any particular type of copulatory behavior, for this is something best worked out between the partners.

6. Abnormalities in the Copulatory Organs and Copulatory Behavior:

     Circumcision, practiced ritually by Jews and Mohammedans, removes the fold of skin which covers the glans. The procedure is usually performed in the infant. It does not seem to influence sexual behavior one way or the other, and it has a very surprising hygienic advantage, which has long been known, and recently explained.

     It has been known for some time that cancer of the penis, which is not rare in uncircumcised people, is virtually unknown among circumcised men. This has been attributed to the accumulation of irritant materials between the foreskin and the glans. On the other hand, cancer of the cervix of the uterus, which is very rare in unmarried women and in women married to circumcised men, is quite common in women married to uncircumcised men. This suggests that an infectious agent accumulated between foreskin and glans may be a fault, and in late 1968, evidence that such an agent existed was reported. The agent appears to be a virus, and it is not certain that it is the causative agent of cervical cancer, but the evidence is certainly suggestive.

     Masturbation substitutes for copulation in the absence of a partner. It does not seem to impair sexual function, mental function, or anything else, though it is widely condemned. It is becoming less condemned now that it is realized that it is virtually universal among boys and very frequent among girls.

     Impotence is the failure of the male to achieve erection in appropriate circumstances. Almost all cases are of psychological origin. Sometimes impotence results from the use of drugs designed to relieve it, notably alcohol, which "provokes the desire and takes away the performance". Surgical sympathectomy, once used in the treatment of hypertension, was often followed by impotence, and some of the anti-hypertensive drugs have the same effect.

     Frigidity is almost always the result of psychological and cultural factors. Unlike impotence, it is difficult to define. In general, it is considered to exist when the female partner expresses a distaste for copulation in advance, responds minimally during the act, and derives no particular pleasure from it. It is not at all clear why sexual activity is disparaged in some cu1tures, but it is very clear that it is considered loathsome and improper by many persons in this culture. Where this attitude exists, it is not surprising that performance and pleasure are adverse1y affected.

     Premature ejaculation may occur during foreplay or very early in copulation. It is primarily a result of youth and inexperience and should not be a cause of great concern though it often is considered evidence of sexual inadequacy by both the male and his partner.

     Changes in aging: Both men and women retain the capacity for sexual performance well into old age. Nevertheless, the frequency of copulation is reduced, and in general, interest is lessened.

     Some physiological factors may be involved in this, though it seems more probable that the dominant factors are psychological and cultural. The subject has not been thoroughly investigated. It is, however, almost certain that the administration of sex hormones is virtually without effect on the sexual responses of aging persons, and such administration may be dangerous in both sexes. Cancerous changes in the prostate may be exaggerated, perhaps even induced by excesses of testosterone, and it is possible that excesses of the ovarian hormones may have the same effect on female cancers.

Continue to Chapter 28.