COLLEGE LEVEL human sexuali ty
Introduction to Human Sexuality www.AudioLearn.com
TABLE OF CONTENTS Preface........................................................................................................ 1 Chapter One: Human Sexuality Anatomy and Physiology ............................ 5 Male Reproductive System .............................................................................................. 5 Female Reproductive System ........................................................................................ 15 The Female Breast ......................................................................................................... 24 Reproductive System Development .............................................................................. 26 The Brain and Sexuality ................................................................................................. 27 Male Circumcision ......................................................................................................... 29 Female Genital Mutilation ............................................................................................. 31 Key Takeaways ............................................................................................................... 33 Quiz ................................................................................................................................ 34 Chapter Two: The Human Sexual Response Cycle ..................................... 36 Sex Drive ........................................................................................................................ 36 Differences in Libido with Gender ................................................................................ 38 Sexual Arousal................................................................................................................ 39 Erogenous Zones ............................................................................................................ 40 Sexual Stimulation ......................................................................................................... 41 Theories on Sexual Responsiveness .............................................................................. 43 More on Orgasm ............................................................................................................ 44 Studying Aphrodisiacs ................................................................................................... 47 Key Takeaways ............................................................................................................... 50 Quiz ................................................................................................................................ 51
Chapter Three: The Psychology of Intimate Relationships ........................ 54 Early Attachment and Intimacy .................................................................................... 54 Attachment Styles in Adults .......................................................................................... 57 The Biology of Attachment ............................................................................................ 58 Attachment in Relationships ......................................................................................... 59 Physical Attraction ......................................................................................................... 60 Male Attractiveness........................................................................................................ 60 Female Attractiveness .................................................................................................... 62 Theories on Love ............................................................................................................ 64 Intimate Relationships .................................................................................................. 66 Non-Monogamous Intimacy.......................................................................................... 69 Key Takeaways ................................................................................................................71 Quiz ................................................................................................................................ 72 Chapter Four: Sexual Behaviors ................................................................ 74 Masturbation.................................................................................................................. 74 History of Masturbation ................................................................................................ 78 Sexual Fantasies ............................................................................................................. 78 Oral Sex .......................................................................................................................... 81 Coitus ............................................................................................................................. 81 Anal Sex .......................................................................................................................... 84 Key Takeaways ............................................................................................................... 87 Quiz ................................................................................................................................88 Chapter Five: Sexual Dysfunction in Men and Women .............................. 90 Hypoactive Sexual Desire Disorder or HSDD ............................................................... 90
Sexual Arousal Disorder ................................................................................................ 92 Anorgasmia .................................................................................................................... 93 Vaginismus ..................................................................................................................... 94 Erectile Dysfunction ...................................................................................................... 95 Premature Ejaculation ................................................................................................... 97 Delayed Ejaculation ....................................................................................................... 98 Key Takeaways ............................................................................................................. 100 Quiz ...............................................................................................................................101 Chapter Six: Sexually Transmitted Diseases and their Transmission ...... 103 Risk Factors for STIs .................................................................................................... 103 Chlamydia .................................................................................................................... 104 Gonorrhea .................................................................................................................... 107 Genital Herpes ............................................................................................................. 108 Hepatitis B ....................................................................................................................110 Syphilis .......................................................................................................................... 112 HIV Disease................................................................................................................... 114 Trichomoniasis ............................................................................................................. 115 Pubic Lice ...................................................................................................................... 116 Human Papillomavirus Infection ................................................................................. 118 Key Takeaways ............................................................................................................. 120 Quiz ............................................................................................................................... 121 Chapter Seven: Contraception, Conception, Pregnancy, and Birth .......... 123 Types of Contraception ................................................................................................ 123 The Process of Conception ........................................................................................... 129
Sexuality in Pregnancy ................................................................................................. 132 Pregnancy ..................................................................................................................... 134 The Birth Process ......................................................................................................... 136 Abortion ....................................................................................................................... 139 Key Takeaways ............................................................................................................. 142 Quiz .............................................................................................................................. 143 Chapter Eight: Gender Expectations and Roles ....................................... 145 Development of Gender ............................................................................................... 145 Development of Gender Identity ................................................................................. 147 Gender Concepts in Children....................................................................................... 148 Gender Roles and Stereotypes ..................................................................................... 150 Transgender Issues ...................................................................................................... 154 Key Takeaways ..............................................................................................................157 Quiz .............................................................................................................................. 158 Chapter Nine: Sexual Orientation ........................................................... 160 Sexual Orientation Explained ...................................................................................... 160 Types of Orientation .................................................................................................... 165 Same-Sex Sexual Behaviors ......................................................................................... 168 Key Takeaways ..............................................................................................................172 Quiz ...............................................................................................................................173 Chapter Ten: Sexuality at Different Ages .................................................. 176 Childhood Sexuality ..................................................................................................... 176 Sexuality in Adolescents .............................................................................................. 179 Aging and Sexuality ..................................................................................................... 183
Aims: ......................................................................................................................... 184 Materials and Methods: ........................................................................................... 184 Results: ..................................................................................................................... 185 Conclusion: ............................................................................................................... 185 Sex and Disabilities ...................................................................................................... 185 Key Takeaways ............................................................................................................. 187 Quiz .............................................................................................................................. 188 Chapter Eleven: Sexual Aggression, Sexual Harassment, Rape, and Child Sexual Abuse .................................................................................. 191 Defining Sexual Aggression .......................................................................................... 191 Sexual Harassment ...................................................................................................... 192 Sexual Assault .............................................................................................................. 194 Rape.............................................................................................................................. 197 Childhood Sexual Abuse ............................................................................................. 200 Key Takeaways .............................................................................................................204 Quiz .............................................................................................................................. 205 Chapter Twelve: Sexual Fetishism and Paraphilic Disorders ................... 207 Sexual Fetishism .......................................................................................................... 207 What is a Paraphilia .....................................................................................................209 Development of Paraphilias......................................................................................... 210 Types of Paraphilias ..................................................................................................... 210 Some Specific Paraphilias ............................................................................................ 213 Key Takeaways ............................................................................................................. 215 Quiz .............................................................................................................................. 216 Chapter Thirteen: Sex Addiction, Prostitution, and Pornography ........... 218
Sex Addiction ............................................................................................................... 218 Prostitution ..................................................................................................................220 Pornography Addiction ................................................................................................ 223 Internet Pornography .................................................................................................. 223 Key Takeaways ............................................................................................................. 225 Quiz .............................................................................................................................. 226 Summary ................................................................................................ 229 Chapter Question Answers ...................................................................... 233 Chapter One ................................................................................................................. 233 Chapter Two ................................................................................................................. 235 Chapter Three .............................................................................................................. 236 Chapter Four ................................................................................................................ 237 Chapter Five ................................................................................................................. 238 Chapter Six ................................................................................................................... 239 Chapter Seven ..............................................................................................................240 Chapter Eight ............................................................................................................... 241 Chapter Nine ................................................................................................................ 242 Chapter Ten .................................................................................................................. 244 Chapter Eleven ............................................................................................................. 246 Chapter Twelve ............................................................................................................ 247 Chapter Thirteen .......................................................................................................... 248 Course Questions and Answers ............................................................... 250 Answers to Course Quiz ...............................................................................................290
PREFACE The purpose of this course is to introduce the student to matters related to human sexuality. The research and understanding of human sexuality are rather recent events compared to the study of other sciences and research is still ongoing. The course touches on the anatomy and physiology of the human reproductive system as well as what is known about the human sexual response, sexual arousal, and intimate relationships in humans. How sexuality figures into contraception, conception, pregnancy, and childbirth are also important issues covered in the course. There are complex issues involving sexual and gender orientation, sexual dysfunction, and behaviors considered to be sexually deviant in today’s society that are part of what is discussed in this course. Chapter one in the course opens up the discussion of human sexuality by talking about the anatomy and physiology of the male and female reproductive system. While not all of sexual behavior and sexuality is focused on the reproductive system, a knowledge of these systems is important to understanding human sex. The study of the brain in human sexuality is not well understood but it is important to recognize its role in sexuality. Some of the cultural issues about the sexual organs is covered in this chapter, including male circumcision and female genital mutilation, sometimes referred to as female circumcision. The topics of chapter two are the human sex drive or libido, sexual responsiveness, and the study of aphrodisiacs. As you will hear, there are differences between men and women when it comes to the sex drive. The sexual response cycle is a relatively predictable pattern of physiological variables that change during sexual activity. There are drugs and supplements considered to be aphrodisiacs. What these substances are and how they are studied are discussed in this chapter. Chapter three in the course looks into the psychology of intimate relationships. Intimacy starts with attachment, and attachment, as you will learn, begins in infancy. The type of attachment a person develops in childhood determines how they will
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respond to intimate relationships in adulthood. Many times, intimacy involves some type of physical attraction, which is discussed in the chapter. There are several theories on what love really is, some of which is neurobiological. The chapter ends with a look at intimate relationships and the different types of intimate relationships that can be part of this or other societies. Chapter four looks into different types of sexual behavior performed in human sexual experience. Sexual behavior can be a singular activity as is seen in masturbation. Some people practice oral sex, which is one of the sections in this chapter. The most common sexual activity in heterosexuals is sexual intercourse, while both homosexual and heterosexual couples can practice anal sex, which is covered in the chapter. The focus of chapter five in the course is sexual dysfunction or sexual disorders in men and women. There are problems associated with low libido or low sexual arousal as well as problems with attaining an orgasm, which are discussed in the chapter. Men can have erectile dysfunction as a sexual problem, while women can have vaginismus that affects sexual satisfaction. Sexual problems in men discussed in the chapter include premature ejaculation and delayed ejaculation. Sexually transmitted diseases and the risks of getting them are the topics of chapter six. As you will learn, certain sexual behaviors predispose a person to getting a sexually transmitted disease and there are ways to decrease their transmission. The different sexually transmitted diseases, which can be viral, bacterial, protozoal, or parasitic, are discussed in the chapter. For a couple of sexually transmitted diseases, there are vaccines that can be used in the prevention of these infections, which are covered in the chapter. Chapter seven in the course encompasses several issues related to conception, pregnancy, birth, and contraception. Many sexually-active couples and single people practice contraception in order to avoid an unintended pregnancy. The process of conception, when it does occur, is discussed in the chapter. The changes seen in pregnancy, including changes in sexuality with pregnancy, are covered. The process of childbirth is explained in this chapter along with the practice of terminating a pregnancy, which is referred to as having an abortion.
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Chapter eight talks about the development of sex differences and gender in humans as well as the different issues that come out of gender identification, such as gender roles and stereotypes. There are individuals who are born with a specific sex assignment who feel as though they do not belong to that gender. These transgender people and their issues are discussed in this chapter. The topic of chapter nine in the course is sexual orientation. This refers to the longlasting sexual or romantic attraction to a person of a certain gender. There is a wide range of choices for sexual orientation, which are described in this chapter. The specific issues related to what it means to be heterosexual, homosexual, bisexual, gay, or lesbian are covered in this chapter as are the different sexual practices involved in sexual relationships between same-sex couples. Chapter ten includes the topics of childhood sexuality, adolescent sexuality, sexuality and aging, and sex among people with disabilities. Sexuality develops first in childhood, usually with sexual curiosity and simple sexual behaviors that develop into adolescent sexual behaviors that increasingly approach adult sexual activity. These are discussed in the chapter as well as the changes in sexuality that occur with aging. Also covered in the chapter is sex in individuals with disabilities. As you will see, sexual behavior persists throughout life and in different life circumstances. The focus of chapter eleven in the course is sexual aggression, which can involve sexual harassment, sexual abuse, rape, and child sexual abuse. In no culture are these things considered to be normal sexual behavior, although it certainly does exist in all societies of the world. Sexual harassment usually involves unwanted sexual attention or behaviors directed at one person by another, often in the workplace. Sexual assault involves many different types of sexual aggression, including rape, which is discussed in the chapter. Child sexual assault is also covered, which involves sexual aggression directed at children. The subjects discussed in chapter twelve include sexual fetishism and paraphilic disorders. The vast majority of sexual fetishes are completely benign and do not necessarily represent a sexual disorder. Paraphilic disorders are intense sexual feelings and behaviors not experienced by most people because of their extreme nature. These
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disorders are usually considered problematic if they cause the individual to have distress about their sexual feelings or behaviors, or if there is a victim involved with the paraphilia. The different fetishes and paraphilias are covered as part of this chapter. Chapter thirteen in the course talks about the interplay between sex addiction, prostitution, and pornography. People with sexual addictions often have impulses and compulsiveness related to engaging in sexual activity. They often turn to soliciting prostitution to handle their need for frequent sexual behaviors, as you will see in the chapter. A related addiction is pornography addiction, some of which is related to internet sex or pornography addictions, which are relatively recent phenomena.
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CHAPTER ONE: HUMAN SEXUALITY ANATOMY AND PHYSIOLOGY This chapter opens up the discussion of human sexuality by talking about the anatomy and physiology of the male and female reproductive system. While not all of sexual behavior and sexuality is focused on the reproductive system, a knowledge of these systems is important to understanding human sex. The study of the brain in human sexuality is not well understood but it is important to recognize its role in sexuality. Some of the cultural issues about the sexual organs is covered in this chapter, including male circumcision and female genital mutilation, sometimes referred to as female circumcision.
MALE REPRODUCTIVE SYSTEM Both the male and female reproductive system have, as their evolutionary function, to produce gametes which, in males, is the male sperm cell or spermatozoon. It takes a single male gamete and a single female gamete to create a zygote, which represents the beginning of human life. The male reproductive tract produces sperm and allows for its transfer to the female, where human life begins. As you will learn, the major hormone responsible for all of male reproductive physiology is testosterone. There are actually several male structures responsible for making, maturing, and transporting spermatozoa. Figure 1 shows the major structures of the male reproductive system:
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Figure 1.
The structures of the male reproductive system include those that can be seen, or what are called the external genitalia, and those that cannot be seen, or what are called the internal structures of the reproductive system. The scrotum can be seen from the outside of the body. It is a pigmented muscular sac that houses the male testes, which are the male gonads. The scrotum is behind and slightly below the penis. It is believed to be located specifically outside the body so that it can keep the testes cooler than the core body temperature by 2 to 4 degrees. This is
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necessary because spermatogenesis or the production of male sperm does not effectively happen at core body temperatures but below this level. Just beneath the subcutaneous muscular layer of the scrotum is the dartos muscle. It is the muscle that helps to create the scrotal septum, which separates the testes into two compartments. There are also two cremasteric muscles that descend from the abdominal muscles to create a net over the testes. Both the dartos and cremaster muscles contract at the same time in order to bring the testes closer to the body when the outside temperature is too cold. These help to regulate testicular temperature. They will relax as well to increase the scrotal surface area in order to increase heat loss in the testes. The median raphe is the visible line that can be seen running up the scrotum centrally. The testes or testicles are the male gonadal structures or the main reproductive structures of the male reproductive system. Testosterone and sperm cells are made in the testes throughout the male lifespan. Men do not stop making sperm as they age, which is different than what you’ll see in women. Each testis is an oval structure about 4 to 5 centimeters in total length. There are two layers of connective tissue around the testes. The outer layer is the tunica vaginalis. It has a thicker parietal layer and a thinner visceral layer. Figure 2 shows these layers around the testes:
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Figure 2.
The inner layer beneath the tunica vaginalis is the tunica albuginea. It is tough and white in color; it directly surrounds the testes and invaginates to divide the testis into about three to four hundred lobules. Inside the lobules are the seminiferous tubules that make the sperm. As you will see, the testes originate inside the abdomen and descend into the scrotal cavity during the seventh month of intrauterine life. If this does not happen, the condition is called cryptorchidism. Most of the testes is made up of seminiferous tubules, which are highly coiled tubes that are involved in sperm cell production. Cells that make sperm gradually mature from the outside of the seminiferous tubules into the lumen or center of the tubules, where they are released. Ultimately, the tubules straighten out to become tubuli recti or straight tubules that together form a meshwork called the rete testes. There are about 20
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efferent ductules that cross over the tunica albuginea, which are the small ducts that the sperm leave from the testes themselves. There are actually six different cell types making up the seminiferous tubules. There are supportive cells called sustentacular cells and different types of germ cells. As mentioned, the germ cells start out least mature in the periphery of the seminiferous tubules and become increasingly mature as they approach the lumen of each tubule. The Sertoli cells are sustentacular cells or supporting cells, found throughout the tubules. They are long and branching so they can come in contact with each germ cell and produce certain signaling molecules that result in sperm production. There is a tight blood-testes barrier formed by tight junctions between adjacent Sertoli cells so that germs, toxins, and antibodies from the bloodstream cannot get to the germ cells. If they do not do their job, autoantibodies to sperm cells can be made, which can greatly affect male fertility. As mentioned, there are different levels of maturation with regard to the sperm cells. The cells closest to the basement membrane on the periphery of the seminiferous tubules are called spermatogonia. These are essentially sperm stem cells that ultimately divide into primary and secondary spermatocytes, then into spermatids, and then into sperm cells themselves. The process that does this is called spermatogenesis. Spermatogenesis does not happen until puberty but will continue throughout the male lifetime. It takes 64 days for the entire process to occur and a new cycle begins every sixteen days. This means that insults to the male reproductive system take about two months to take effect. Advancing age will reduce the sperm count, with reductions after thirty-five years of age. Things like smoking can also lower sperm counts as well. Meiosis is a special type of cell division that only happens to reproductive cells. They start out as diploid, which means they have 46 human chromosomes representing the man’s genetic material. Through the process of meiosis, which includes genetic rearrangement of genes on the chromosomes, a total of 4 haploid sperm cells or male gametes are formed. Haploid means they have just 23 chromosomes, which potentially combine with female chromosomes in the egg cell to make a diploid human cell unique from all others. Figure 3 shows the process of meiosis:
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Figure 3.
When spermatogenesis occurs, the spermatogonium divides into two identical cells. One cell remains a stem cell, while the other becomes a primary spermatocyte, continuing on to mature further into sperm cells. The process of spermiogenesis is not the same thing as spermatogenesis. Spermiogenesis is the creation of what is seen as a sperm cell, with reduced amounts of cytoplasm and the start of what becomes a sperm cell with a tail. Sperm cells are small—so small that they are more than 85,000 times smaller than the female egg cell. Every man makes up to 300 million sperm per day. They are distinct in their structure because they have a head, a cap called an acrosome, and a tail. The
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acrosome contains special enzymes that will help the sperm to penetrate the egg cell. There are a lot of energy-producing mitochondria in the midportion of the sperm. These will make ATP energy that drives the tail or flagellum. The flagellum allows the sperm cell to move. There is an axial filament that drives the flagellum. Figure 4 shows the structure of the sperm cell:
Figure 4.
The sperm cells need to get from the seminiferous tubules to the outside of the body. The process of this is called ejaculation. The sperm are completely immobile when they leave the testes. They travel for maturation in the epididymis. The epididymis is a coiled tube behind the testis where sperm cells mature. There are twenty feet of total epididymis distance, even though it is tightly coiled and appears small. It takes about 12 days for the sperm to travel through this structure, where it develops a tail and the ability to mobilize itself.
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The sperm exit the epididymis through the vas deferens, which is a muscular tube that is sometimes cut to ensure male sterility in a procedure called a vasectomy. The vas deferens—one for each testis—enters the abdomen through the inguinal canal and comes toward the middle, where semen is made. Semen is 95 percent something other than sperm cells. It is the milky substance that men ejaculate out of the penis. There are several things that happen to make semen. First, the sperm are mixed with fluid in the seminal vesicles, which are paired glands that contain fructose—a type of sugar that nourishes the sperm cells as they progress through the reproductive system. The two ducts become ejaculatory ducts that send the semen to the prostate gland. There is just one prostate gland, which surrounds the urethra at the base of the bladder. The prostate gland secretes an alkaline fluid so that another component of semen is created. The alkaline fluid helps to coagulate and uncoagulate semen after ejaculation. The semen is first coagulated in the female vagina so it doesn’t fall out and then it uncoagulates to allow sperm to travel into the female reproductive system. The semen is considered in its final state after it passes through the Cowper’s glands or bulbourethral glands. They make a salty fluid that acts as a lubricant for the semen. It is only when the male is sexually aroused that the Cowper’s glands add their component. Prior to this point, the semen is called pre-ejaculate. A woman can get pregnant from pre-ejaculate fluid, even if the man does not actually ejaculate. The penis is the copulatory organ of the male reproductive system. Most of the time, it is flaccid but becomes turgid and rod-shaped during sexual arousal. The stiffness is caused by an increase in blood flow in the penis in order to allow it to penetrate the vagina and deposit semen into the vagina. Figure 5 shows the internal structure of the penis:
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Figure 5.
The penile shaft surrounds the male urethra. In the shaft, there are three columns of erectile tissue. The lateral chambers are called the corpora cavernosa, which make up most of the penis. The corpus spongiosum is a single shaft that surrounds the urethra itself. The end of the penis is called the glans penis. This is the part of the penis that contains the most nerve cells and is the most sexually sensitive. The prepuce or foreskin covers the glans like a collar. It is removed during a circumcision but also contains nerve endings and a means of lubrication of the glans. The foreskin retracts during sexual arousal. Figure 6 shows what a circumcised and uncircumcised penis looks like:
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Figure 6.
The penis becomes erect and engorged because of a release of nitric acid from the nerve endings in the area of the corpora cavernosa and the corpus spongiosum. This causes dilation of the arteries leading to the penis and an increase in blood volume that causes blood to fill the erectile chambers of the penis. The veins exiting the penis are compressed so that there is an excess of blood inside the penis itself. As mentioned, the main androgen hormone in the male reproductive system is testosterone. This is made by the Leydig cells between the seminiferous tubules. This production of testosterone in the male embryo at about seven weeks’ gestation is what triggers the development of the male genitalia. Testosterone increases during puberty in order to cause spermatogenesis and the development of the male sex characteristics. Males produce between six and seven milligrams of testosterone per day. It is the hormone responsible for libido or sex drive in both men and women. It is the hormone necessary for muscular development, bone growth, and the development in puberty of 14
secondary sex characteristics. You should know that, in women, testosterone is also secreted by the female ovaries but in a smaller amount than is seen in males. The endocrine system controls the production of testosterone. It all starts with the release of gonadotropin releasing hormone or GnRH from the hypothalamus. This happens steadily in males but is cyclical in females. The GnRH causes the pituitary gland to make follicle stimulating hormone or FSH and luteinizing hormone or LH. The FSH is responsible for Sertoli cell function and spermatogenesis. Sertoli cells make inhibin, which is a peptide hormone that feeds back to block FSH release. The LH triggers the Leydig cells to make testosterone. The entire process is a type of negative feedback system. Low testosterone concentrations will increase GnRH production by the hypothalamus, which sets the process in motion. When testosterone levels are considered high enough, the testosterone will block both the GnRH release and the LH release. The same thing happens to the feedback loop involved in FSH secretion.
FEMALE REPRODUCTIVE SYSTEM The female reproductive system is responsible for making the female gamete, which is called an oocyte. There are internal and external structures in the female reproductive system. Figure 7 shows the external genitalia in the female:
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Figure 7.
The vulva is the female external genitalia. There is the mons pubis, which is the fat pad that covers the pubic bone in front. This will be covered with pubic air after puberty. The labia minora or larger lips are hair-covered folds on either side of the vagina. Just inside these are the labia minor or minor lips. Each of these protect the urethra and vagina. Coming together in the front or anterior of the labia minora is the clitoris. This is embryologically the same tissue as the glans penis in men and is extremely sensitive with nerve endings. The clitoris is erectile and will swell with stimulation. It has a tissue
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fold covering, called the prepuce. The clitoris is the most important structure in aiding female orgasm. There are corpora cavernosa, which are also erectile, extending on either side of the vulva. The hymen is a membrane that covers, at least in part, the vaginal opening until it is disrupted, usually when the woman first has intercourse. The urethra is where urine exits. It is located in the anterior part of the vaginal introitus or vaginal opening. On either side of the vaginal opening are lubricating glands called Bartholin glands, which are not visible under normal circumstances. There are lesser mucus-secreting glands near the clitoris. The perineum is the tissue space between the vulva and the anus. This is the part that is cut when a woman has an episiotomy at the time of birth. The vagina opens at the vaginal introitus. It is a ten-centimeter muscular tube that becomes the entrance to the reproductive tract. It is where the fetus and menstrual blood exit the body. There are rugae or transverse folds that make the surface rough in texture. The fornix is the very top of the vagina. This is where the cervix protrudes into the vagina. The cervix is smooth rather than rough, making it easier to identify. The muscles and rugae allow the vagina to expand during sexual excitement and childbirth. The vagina is not a sterile environment but has a collection of normal bacteria and other organisms that prevent other, more serious organisms from gaining traction in the vagina. Most of these bacteria are called Lactobacillus, which secrete lactic acid as part of their metabolism. This has the effect of lowering the pH of the vagina. This acidity prevents the alternative growth of pathogenic bacteria. Douching will disrupt this milieu and can lead to an increase in infections. The female gonads are called the ovaries. These are oval and located on either side of the uterus, being about two to three centimeters in length. There is part of the abdominal peritoneum called the mesovarium; this will help to support the position of the ovaries. There is also a suspensory ligament that helps to connect the ovary to its blood and lymph vessels. Third, there is an ovarian ligament that attaches the ovary to the uterus.
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There is an outer epithelial layer on the ovarian surface, underneath which is the tunica albuginea, which is a tough layer of connective tissue around the ovary. Beneath this is the cortex, which is the framework for the germ cells and supportive cells. A combination of the oocyte plus its supportive cells is referred to as a follicle. Figure 8 is what an ovarian follicle looks like:
Figure 8.
The ovary goes through a natural ovarian cycle, which leads to a mature egg. The cycle happens only during the reproductive years and completes itself every twenty-eight days. This is not exactly the same thing as the menstrual cycle. The two parts of this cycle are related to oogenesis or egg-making and folliculogenesis or follicle-making. As in the male testes, there are stem cells or germ cells called oogonia, which are formed in fetal life. They divide normally in the process of mitosis but become primary oocytes before birth. This is where they stop developing and remain until the process of meiosis resumes after puberty. Most of the egg cells are present at birth but decline to be about 400,000 in total at the time of puberty. This number becomes zero at the time of menopause. 18
Ovulation is the release of an oocyte from the ovary. This happens for the first time at puberty and again happens about every 28 days until menopause is reached. Luteinizing hormone triggers meiosis to continue in the primary oocyte to make the secondary oocyte. The main difference between men and women is that, while men create four equal sperm cells, the process of oogenesis gives rise to just one mature egg cell and three polar bodies, which are inactive cells that disintegrate. Interestingly, the secondary oocyte does not complete meiosis until the sperm cell has penetrated the egg cell. These leads to a haploid ovum plus a polar body. The haploid ovum combines with the haploid sperm cell to become a zygote. As you can imagine, this haploid ovum state is very brief. The female gamete or ovum is very large. It contains all the mitochondria and organelles not found in the sperm cell. Mitochondria have their own DNA, which is passed on to the offspring. In fact, mitochondrial DNA analysis can look specifically at the ancestry of a child along the maternal lines. Folliculogenesis is the development and maturation of the oocytes and the supportive cells. One follicle matures every 28 days in women of reproductive age. There are other follicles developing at the same time but most of these undergo atresia, which is regression and disintegration. There are primordial follicles, primary follicles, secondary follicles, and tertiary follicles. The oocyte stays inside the follicle until the time of ovulation. Primordial follicles are found in newborn babies and in adults. There is a single layer of supportive cells called granulosa cells around the oocyte. Primordial follicles often remain this way for years. After the time of puberty, some of the primordial follicles will be recruited to make primary follicles. The granulosa cells thicken and proliferate. These follicles become secondary follicles and a new layer of estrogen-producing cells called theca cells begin to do their job. There is a thin membrane around the primary oocyte called the zona pellucida. This is the layer that gets broken down by the enzymes in the acrosome of the head of the sperm cell. Follicular fluid is made to create a space called the antrum, which enlarges the follicle. This tertiary follicle is called an antral follicle. There are several antral
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follicles made per cycle but must will undergo atresia, leading to a dominant follicle. Only one percent of follicles will completely mature. Atresia can happen at any time in folliculogenesis. There is a great deal of hormonal control over this ovarian cycle. It takes about two months from the time of the primordial follicle to the time of the tertiary follicle. It is the secondary oocyte that gets ovulated every month. There is GnRH, exactly as in men but it is released in a cyclical fashion by the hypothalamus. This leads to FSH and LH to be released by the anterior pituitary gland. FSH contributes to folliculogenesis, while LH stimulates the release of female sex hormones. There is a similar feedback loop regarding these hormones in females as there is in males. The feedback mechanism contributes to the survival of just one follicle per cycle. The surviving follicle is called the dominant follicle, which continues to secrete estrogen. It creates a great deal of estrogen that overrides the feedback loop and actually becomes a positive feedback loop, leading to a surge in luteinizing hormone, called the LH surge. It is the LH surge that triggers ovulation. It also triggers protein-degrading enzymes to break down the follicle wall so the oocyte can be released in the process of ovulation. After the oocyte has been released, there is a change in the granulosa cells and theca cells, which undergo luteinization, causing them to secrete progesterone as a dominant hormone. Then the follicle remnants are called the corpus luteum. Progesterone increases the woman’s body temperature slightly and will support the beginnings of a pregnancy. If no pregnancy happens, the corpus luteum stops making progesterone and the menstrual flow begins. Progesterone also suppresses the development of more dominant follicles. The corpus luteum ultimately degrades into a nonfunctional corpus albicans. Figure 9 shows the internal structure of the female reproductive system:
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Figure 9.
The uterine tubes are also called the oviducts or fallopian tubes. These are passageways for the egg from the ovary to the uterus and is where fertilization takes place. There are several parts to the fallopian tubes. The fimbriae are on the far outer side. They are fingerlike projections that embrace the ovary to sweep in the oocyte as it is being released. The oocyte enters the wider infundibulum and then the ampulla in the middle, where fertilization occurs. The isthmus is the connecting piece to the uterus. There are cilia and contractions of the fallopian tubes that coordinate to push the otherwise immotile oocyte down the tube. You should know that the oocyte is actually ovulated into the peritoneal cavity. It is only because of the fimbriae activity that the egg is swept into the fallopian tube itself. The sperm travel up into the tube to fertilize the moving egg. Once the oocyte is fertilized, the zygote successively divides into twos, fours, eights, etcetera. It will ultimately implant in the uterus. The egg that does not get fertilized degrades within one to two days after ovulation. Sperm cells survive longer than egg cells before disintegrating. The uterus is where the embryo and fetus develop. It is about the size of a fist in the nonpregnant state and is highly muscular. There are three sections to it. The fundus is the top part above where the tubes enter the uterus. The body is the main, central part of
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the uterus. The cervix is narrow and protrudes into the vagina. It produces secretions that change in character, depending on the stage of the woman’s menstrual cycle. When it becomes clear and stretchy, the woman can get pregnant as this fluid best supports the passage of sperm cells. There are three layers in the uterus. The perimetrium is the outermost layer, which is basically a thin, serous membrane. The middle layer is the myometrium, which contains all the muscles of the uterus. These muscles stretch greatly in pregnancy and contract forcefully in labor and during the menstrual period. The endometrium or inner lining has two layers itself. The stratum basalis is near the myometrium and doesn’t shed each menstrual period but the stratum functionalis will shed each time the woman has her period. This inner layer changes greatly in character in different parts of the menstrual cycle. The stratum functionalis thickens in the follicular or beginning part of the menstrual cycle. Once progesterone is made by the corpus luteum, the stratum functionalis changes in character to become secretory and more mature for implantation. If the corpus luteum degrades, the endometrium thins out and the spiral arteries feeding it constrict and break open. Prostaglandins, which are what cause menstrual cramping, contribute to this process. The stratum functionalis dies off and gets shed during menses. The first period a girl has is called menarche. The menstrual cycle is considered different from the ovarian cycle but, of course, these are related. It refers to the changes in the endometrial lining and pelvic structures over the course of a month. The first day of bleeding is called day 1 of the menstrual cycle. A typical menstrual cycle is 28 days but this can be longer or shorter than that, depending on the women and specific circumstances. These difference in cycle length are generally due to shortening or lengthening of the first half of the cycle and not the second half, which is almost always 12 to 14 days in total length. The menses phase is when a woman bleeds. This often lasts between 2 and 7 days, with an average of five days. The uterine lining is shed and the LH, FSH, and progesterone levels are very low. In fact, it is the sharp decline in progesterone secretion that triggers menses. Figure 10 shows the different phases of the menstrual cycle:
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Figure 10.
The proliferative phase starts next. The granulosa cells and theca cells make more estrogen, which thickens the uterine lining. This continues to grow until the LH surge, when the ovulation phase takes place. When ovulation happens, the proliferative phase is over. After ovulation is the secretory phase of the menstrual cycle. The vagina becomes more hospitable to sperm about the time of ovulation and then the corpus luteum begins to make progesterone. The secretory phase is what prepares the uterine lining for implantation. Glycogen is secreted by the uterine glands that will ultimately nourish the zygote after implantation. The spiral arteries develop to supply blood to this tissue.
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THE FEMALE BREAST The breasts are accessory organs of the reproductive system in females but they can be important sexually. The areola is the pigmented area surrounding the nipple; it is sexually sensitive. There are raised areolar glands that secrete a lubricating fluid that protects the areola during suckling. The entire areola is taken up by the baby’s mouth during breastfeeding. Breast milk is made by the female mammary glands, which are in effect sweat glands that have been modified to produce milk. There are about twenty lactiferous ducts that open out into the nipple. Inside the breast itself, the lactiferous ducts open into lactiferous sinuses that lead to lobes containing clusters of cells that make milk. The cells are arranged in alveoli, which are the actual cell clusters. There are myoepithelial cells around the alveoli that contract to eject milk into the lactiferous sinuses, where it is further drawn out by the action of suckling. The rest of the breast is made by fat, which is what determines the actual size of the breasts. This means that larger breasts do not put forth more milk than smaller breasts. There are suspensory ligaments that hold the breasts in place. Figure 11 shows the anatomy of the breasts:
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Figure 11.
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REPRODUCTIVE SYSTEM DEVELOPMENT The reproductive system develops in the first few weeks of gestation. After one month in utero, primordial gonads develop. While this changes during gestation, very little change happens between infancy and puberty. All embryos start out life as phenotypic females so that, if there is no chemical intervention, the infant would appear female at birth. The male Y chromosome has a special gene called the SRY gene. Both male and female gonads have early cells that have the potential to be either gender but the SRY gene recruits other genes, leading to a gene cascade. This gene cascade causes spermatogonia to form. If this doesn’t happen, then oogonia and an ovary develops instead. Leydig cells develop in the testes, which make testosterone. This helps to cause the male sexual structures to form. Without testosterone, the glans penis would otherwise be the glans clitoris. There are two separate ducts for the male and female reproductive system. Female organs are derived from the Mullerian duct, while male organs are derived from the Wolffian duct. The two ducts cannot grow simultaneously. The Mullerian duct will degenerate when the Wolffian duct develops and vice versa. It is testosterone that triggers the Wolffian duct to develop. If testosterone does not get made, the Wolffian duct will degenerate. Puberty is the time of further sexual maturation. The hormonal control of the boy and girl are similar but the outcome is different. The release of GnRH by the hypothalamus stimulates the onset of puberty. This triggers the events that happen to develop the secondary sex characteristics in adolescence. At the age of eight or nine, LH first becomes detectable, even before there are physical changes. The sensitivity of the feedback system during this time is quite high so it doesn’t take much testosterone or estrogen to feed back onto the hypothalamus and pituitary to shut off LH, FSH, and GnRH production. This sensitivity decreases near puberty and the gonads are more sensitive to LH and FSH. This leads to enlargement of the gonads.
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Genetics, psychological stress, and nutrition contribute to the age at onset of puberty. The average age at menarche is 12.75 years but it was much higher 150 years ago, when nutrition was poorer. The amount of fat stored in the body will help to determine whether puberty occurs in girls. It is believed that leptin, a hormone made by fat cells, helps to determine the age of menarche. Girls who are thin and active will have delayed menarche. The secondary sex characteristics develop at the time of puberty. In males, these characteristics include increased laryngeal size, which deepens the voice, greater muscle development, and the growth of pubic hair, facial hair, and overall body hair. In females, it is increased fat deposition in the hip and breast area, increased breast size, and broadening of the female hips. Pubic and axillary hair develop. The growth spurt in girls happens prior to the onset of menarche with breast development being the first sign. In males, the first sign is the growth of the testes. The first fertile ejaculate happens at around 15 years of age.
THE BRAIN AND SEXUALITY The brain is involved in all aspects of sexual behavior, from the onset of desire to orgasms and the need to cuddle. Researchers have done neuroimaging studies on human sexual behavior, which looks for the changes in the brain during sex in men and women. There is a four-component model that has been developed to try to understand the role the brain plays in sexual responsiveness. The first stage is cognitive or the thinking phase. It involves the perception of the visual sexual stimulus, deciding if it causes sexual feeling. The ventromedial prefrontal cortex in the front of the brain is connected to the limbic system, which is the emotion system of the brain, as well as certain parts of the brain associated with the senses. The end result is the focusing of the attention toward the sexual stimulus, which activates both the occipital lobe, involved in vision, and the temporal lobe, involved with hearing. There is a specific extrastriate body in the brain that is connected to perceiving the human body.
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The next stage is the emotional component, which involves mainly the limbic system. The amygdala is part of this system. It interacts with the ventromedial prefrontal cortex to control the processing of senses. The amygdala is highly connected to motivation so it helps to guide sexual behavior. Interestingly, if the amygdala is deactivated, this is what’s seen in patients who have indiscriminate sexual behavior and hypersexuality. Two of these syndromes are called Kluver syndrome and Bucy syndrome. The emotional part of this phase isn’t strictly so because it is also tight to the genitalia and the physical feelings of sexual pleasure. The next stage is motivational, which is also highly dependent on the limbic system. Parts of the hypothalamus, thalamus, and anterior cingulate cortex get activated in this stage. This leads to the motivation toward reaching a sexual goal. Sexual urges, the need for reward, and sexual desires come at this time. Lastly, there is the physical or physiological component. This involves hormonal changes, high blood pressure, racing heart, and genital responsiveness. Sexual arousal occurs to prepare the body for sex. This is all activated in the brain to generate the hormonal and autonomic responses to arousal. The hypothalamus is particularly important because it controls the parasympathetic and sympathetic nervous systems— two parts of the involuntary autonomic nervous system—which get activated during sex. There are also inhibitory processes that help us control our sexual behavior so that not all urges are satisfied. If these processes are too activated, there may not be a gratifying sexual experience. If the anterior cingulate cortex and ventromedial prefrontal cortex are damaged, there can be the onset of excessive pleasure-seeking behavior that might be socially inappropriate. In general, women have weaker brain responsiveness to visually erotic stimuli. While most researchers believe there are real differences in sexual brain activity and activation between men and women, these types of studies have not yet been done. Most studies have been done on heterosexual males and haven’t compared the two genders. It appears that women are more complex when it comes to sex than men. Men more easily respond to visual sexual stimuli, when women have a stronger response to the sense of smell of their sexual partner. Women also respond more to erotic videos that
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have an emotional component or a story, while this just isn’t the case with men. Interestingly, women are less sexually aroused during the follicular phase of their cycle, which may play a role in being selective about one’s mate. Men have a strong neural reaction when exposed to a specific sex but not to the other sex, while women respond similarly to erotic stimuli that involve either sex. This appears to be true of both homosexual and heterosexual individuals of both genders. Patterns of orgasm, on the other hand, are the same between men and women. During orgasm, the amygdala and ventromedial prefrontal cortical areas shut down immediately—similar to taking heroin. This accounts for the disinhibition that transiently occurs during orgasm. After orgasm, there is the experience of an endorphin rush and releases of oxytocin and prolactin. This differs between men and women and isn’t completely understood. It is believed that these hormones contribute to increased bonding and to post-coital cuddling behavior seen in some individuals.
MALE CIRCUMCISION As mentioned, male circumcision is the removal of the foreskin from the glans penis. There are specialized devices used in the newborn period to crimp off the foreskin. No actual stitching is involved. The blood flow to the foreskin is cut off and the remaining devitalized foreskin is removed. This is an elective procedure done for medical, social, or religious reasons. It can be done as an emergent or relatively urgent procedure if the foreskin gets trapped in the retracted position, called paraphimosis, or if there are chronic bladder infections. The elective circumcision done at birth is done for the parent’s personal preference or for religious reasons. Societal norms drive the desire to have a child circumcised. It is considered to have a modest health benefit. It will decrease the incidence of HIV disease so it is done more often in Africa, where the prevalence of HIV is higher. There are no medical organizations that have either supported or banned circumcision in modern time. It cannot be done if there are birth defects involving the penis or in known bleeding disorders.
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There is a decreased risk, not only of HIV disease, but of certain types of human papillomavirus infections, syphilis, genital herpes, and chancroid in men who get circumcised. There is mixed evidence that it protects against other sexually transmitted diseases and it does not decrease the risk of getting gonorrhea. If the penis cannot be retracted, this is called phimosis, for which circumcision is recommended. Forced retraction of the foreskin and infections of the foreskin are other reasons to have a circumcision. While circumcision will decrease the risk of penile cancer, it will not completely protect against it. About 38 percent of males in the world are circumcised, with half being done for cultural or religious reasons. The rate is highest among Muslims, in Africa, in Israel, in South Korea, and in parts of the United States. It is rare in Europe, Latin America, Oceania, and Asia. Circumcision is believed to have happened in prehistoric times. It spread from geographical area to geographical area. It was practiced by Ancient Egyptians and was picked up by Muslims and Jewish people. It was practiced by Australian Aborigines and by the Polynesians. It is believed to have been practiced by the Mayans and Aztecs. Some Native American peoples practiced circumcision. In more modern times, circumcision became popular by Westerners in the late 19th Century, when doctors believed it would deter masturbation. At the time, masturbation was felt to cause a variety of mental and physical conditions. It was later felt to be healthier for the penis to be circumcised because the smegma, which is the whitish substance beneath the foreskin, was believed to cause disease. Circumcision is a part of culture and religion. It is practiced specifically in today’s society by people in the Islamic and Jewish faith. In the Jewish faith, it is done on the eight day of a child’s life and must expose the glans penis entirely. In the Islamic faith circumcision is universal and is believed to lead to cleanliness and purity. It is done up to 15 years of age and is thought to be related to being able to recite the Quran. It is not practiced by most Christians as part of their religion. Certain cultural groups in Africa have circumcision as a custom. It does not always have religious significance but is primarily cultural in origin. In some cultures in Africa, many
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boys of different ages are circumcised at one time. It is still practiced by Australian Aborigines as a test of self-control and bravery. It is part of a wider tradition that includes scarification of the body. Most Filipino men are circumcised during the springtime months. The circumcised boy is treated as an adult after the procedure is done.
FEMALE GENITAL MUTILATION This practice is also sometimes referred to as female circumcision. It removes some or a portion of the external female genitalia. It is mainly done in parts of Asia, Africa, and the Middle East, where it is believed to have affected 200 million living women. It can be done at birth or even beyond puberty but is primarily done before five years of age. The procedure involves removal of the clitoris, clitoral hood, inner labia and outer labia, with closure of the vulva, although there are different degrees of severity. It leaves behind a small hole that will allow for urination and menstrual blood. The vagina is later opened for intercourse and childbirth. Much of the practice is related to certain cultural ideas about modesty, beauty, and purity as well as an attempt to control female sexuality. The practice is actually done by women who fear that failing to do the procedure would alienate the child culturally. Side effects include problems urinating, infections, chronic pain, and incomplete passage of menstrual flow. The most common type of this procedure performed involves complete or partial excision of the glans clitoris. This is called type I. In type II excisions, the inner labia and sometimes the removal of the clitoris and external labia are performed. Type III is referred to as infibulation, where the remaining portions of the external genitalia are sewn together. The remaining hole is about 2 to 3 millimeters in diameter. This is primarily done in Africa. The genitals are opened up by a midwife or by the woman’s husband. Some women have it repeated after childhood, widowhood, or divorce. In cultures where infibulation is more common, both men and women tend not to like the sight of a natural women’s vulva and there is a preference for dry sex as well as a dry vaginal area without any odor. Some women will insert things, such as tree bark, Vicks
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menthol rub, and toothpaste in order to reduce the vaginal lubrication. It is believed by both men and women that infibulation allows for better hygiene. Women also cite things like cultural acceptance, religion, marriageability, and preservation of virginity as reasons for the procedure. In some cultures, such as Egypt, it is seen as a religious obligation.
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KEY TAKEAWAYS •
The male gonads are the testes, which produce spermatozoa and testosterone.
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The mature sperm cell swims with a flagellum; it is mixed with several fluids to make semen.
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The male copulatory organ is the penis, which has most of the nerve endings. It must become turgid in order to penetrate the vagina.
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The female gonads are the ovaries, which produce ova, estrogen, progesterone, and a small amount of testosterone.
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Testosterone is necessary for both male and female libido.
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The female menstrual cycle sets the uterus and ovaries up for fertilization; menses occurs when fertilization does not occur.
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Much of sexuality and sexual feelings originates in areas of the brain linked to attention, motivation, and emotions.
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Male circumcision removes the male foreskin. It is primarily done for cultural and religious reasons, although there are a few health benefits.
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Female genital mutilation is practiced in upper and middle Africa and in parts of the Middle East, where it is believed to be a hygienic and culturally-positive thing to do.
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There are many long-term and short-term complications of female genital mutilation so that it is discouraged by all world organizations and is not practiced in most societies of the world.
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