Introduction to Human Sexuality Part I Chapter 4 Sex Differentiation, Anatomy, and Physiology

CHAPTER Chapter Sex Differentiation , Anatomy , and Physiology , AND EMERSON WOLFE , CHAPTER LEARNING OUTCOMES EVERY Distinguish between female , male , and intersex anatomy and recognize the differences and similarities between them Identify hormones that influence sex development and sexual behavior Explain how tissues are directed to develop into male or female sex organs Name the rudimentary duct systems in the embryo that are precursors to male or female internal sex organs Describe the hormonal changes that bring about puberty , and the secondary sex characteristics of men and women Analyze the complexity of sex development and gain an understanding ofthe experiences of intersex and transgender individuals Describe the sexual response cycle Evaluate theories explaining the sexual arousal and response processes , such as Masters , the stages of physiological arousal , etc . Distinguish between pleasure and reproduction as motives behind sexuality BODY IS DIFFERENT . BUT MANY THINGS ABOUT OUR BODIES ARE THE SAME . Humans come in a variety of shades , sizes and proportions , yet in total , our bodies are more similar to each other than they are different . In fact the human body shares similarities with bodies across the diversity of life . We share aspects of our reproductive system with all mammals , aspects of our basic physiology with all vertebrates , and aspects of our cell structure , biochemistry and genetics with all living things . In this chapter , we will look at the human body specifically , not because the human body , in terms of reproduction , is very distinct from that of a sloth , or because the basic structure is very different from a tortoise , or because our cellular biology varies much from that of the fungus that inhabits bleu cheese . Instead , we focus on the human body 40

SEX DIFFERENTIATION 41 because the authors and readers of this text presumably each have a human body , and reading about ourselves is interesting . AUTHOR NOTE Some of the language in this chapter is still held in the binary that is or female . This is concurrent with a lot of medical literature . importantly , however , even biological sex is found on a continuum so there are variations of genital structure and presentation that defies the binary , which is critical to note . SEX DIFFERENTIATION Sex differentiation , also referred to as sexual differentiation , is the process in which genitals and reproductive organs develop within the womb as a result of complex hormonal processes altering neutral tissues to develop along female and male lines and in which varying combinations are possible as well . Secondary sex characteristics begin to develop further as part of the sex differentiation process during puberty . Therefore , prenatal development , as well as changes that further occur during puberty , create a cascade of events that results in physical changes to the body . Chromosomes , genes , gonads , hormones , and hormone receptor sites play key roles within the endocrine system that influence sex development . Sex is both a genetic and environmental experience in which epigenetic factors can alter the way that genes function , resulting in changes to hormone production and hormone receptor sites at different points across the lifespan . Prenatal between male and female reproductive anatomy During embryonic development the male and female fetus are indistinguishable before about 10 weeks of pregnancy . Fetal tissues begin in an undifferentiated state , and based on genetic signals and the environment the reproductive organs usually differentiate into structures typical of males and females . This means that for most of the reproductive parts there is an analogous part in the other sex that arose from the same original tissues . For example , testes and ovaries develop from the same tissue originally located in the abdomen . in males the testes move down and outside the abdomen as they develop in female they remain internal . Some structures ( such as the ) have a structure that was common in early development , but completely or partially disappears in later development other structures ( such as the uterus ) have that are very subtle structures in the male . See the following table for a list structures in male and female anatomy .

42 EMERSON WOLFE , Godhead 7005 Some analogous structures in male and female anatomy Undifferentiated Genital Genital fold Gum , Male Female Guns Cold groove ?

swelling 99 Shaft at was urethral ' Phenotypic of the external genitalia in male and female embryos Image by . License Commonalities between male and female reproductive signaling Much of the reproductive physiology we will address is regulated by hormonal signals that arise in the brain and much of this signaling is shared between males and females .

SEX 43 Within the brain is a region called the hypothalamus ( see figure below ) This portion of the brain sends signals to the pituitary gland located beneath it . In particular , the hypothalamus sends a hormonal signal called hormone ( to the pituitary gland . In response to the signal , the pituitary gland releases two hormones that circulate in the blood hormone ( and follicle stimulating hormone ( These hormones travel throughout the body , triggering further hormone releases and physiological changes ( discussed further below ) There are feedback loops that tightly regulate the levels of circulating hormones . In addition to , and , the hormones testosterone , estrogen and progesterone are important in reproductive signaling . While we will focus on the effects of testosterone in males and estrogen and progesterone in females , all ofthese hormones are present and important in both males and females . Further Sexual Development Occurs at Puberty Puberty is the stage of development at which individuals become sexually mature . Though the outcomes of puberty for boys and girls are very different , the hormonal control of the process is very similar . In addition , though the timing of these events varies between individuals , the sequence of changes that occur is predictable for male and female adolescents . As shown in the figure below , a concerted release of hormones from the hypothalamus ( the anterior pituitary ( and ) and the gonads ( either testosterone or estrogen ) is responsible for the maturation of the reproductive systems and the development of secondary sex characteristics , which are physical changes that serve auxiliary roles in reproduction . The first changes begin around the age of eight or nine when the production of becomes detectable . The release of occurs primarily at night during sleep and precedes the physical changes of puberty by several years . In children , the sensitivity of the negative feedback system in the hypothalamus and pituitary is very high . This means that very low concentrations of or will negatively feed back onto the hypothalamus and pituitary , keeping the production , and low . As an individual approaches puberty , two changes in sensitivity occur . The first is a decrease of sensitivity in the hypothalamus and pituitary to negative feedback , meaning that it takes increasingly larger concentrations of sex steroid hormones to stop the production of and . The second change in sensitivity is an increase in sensitivity of the gonads to the and signals , meaning the gonads of adults are more responsive to than are the gonads of children . As a result of these two changes , the levels of and slowly increase and lead to the enlargement and maturation of the gonads , which in turn leads to secretion of higher levels of sex hormones and the initiation of spermatogenesis and . In addition to age , multiple factors can affect the age of onset of puberty , including genetics , environment , and psychological stress . One of the more important influences may be nutrition historical data demonstrate the effect of better and more consistent nutrition on the age of menarche in girls in the United States , which decreased from an average age of approximately 17 years of age in 1860 to the current age years in 1960 , as it remains today . Some studies indicate a link between puberty onset and the amount of stored fat in an individual . This effect is more pronounced in girls , but has been documented in boys as well . Body fat , corresponding with secretion of the hormone by adipose cells , appears to have a strong role in determining menarche . This may reflect to some extent the high metabolic costs of gestation and lactation . In girls who are lean and highly active , such as gymnasts , there is often a delay in the onset of puberty .

44 EMERSON WOLFE , Hung Eu . I . i I Ea ' lI ' I ' PI ' Emmy ' I ' FE ' There are around 50 different kinds in the human body . and under the terms of the Creative Commons Attribution License ( BY ) Hormones of Puberty During puberty , the release of and from the anterior pituitary stimulates the gonads to produce sex hormones in both male and female adolescents . Signs of Puberty Different sex steroid hormone concentrations between the sexes in general and within each individual uniquely also contribute to the development and function of secondary sexual characteristics . Examples of secondary sexual characteristics are listed in Table . Each hormone concentrations will depend upon genetics , diet , stress , and more thus , secondary sex characteristics will progress along a continuum of possibilities based on these nature multiplied by nurture combinations . Development of the Secondary Sexual Characteristics Male Female Increased larynx size and deepening of the voice Deposition of fat , predominantly in breasts and hips Increased muscular development Breast development Growth of facial , axillary , and pubic hair , and increased growth of body hair Broadening of the pelvis and growth of axillary , pubic and body hair Something to keep in mind as well is that people can experience varying degrees of muscular , breast and hair development depending upon their genetic and environmental makeup . For instance , some boys at the beginning of puberty may see breast tissue growth as well as other body fat increases , and some girls may have facial and body hair growth . One example in this complex process is how unused testosterone is converted to estrogen , for instance , making it not about how much testosterone is present and rather how that testosterone is being used or unused . Also , hormone receptor sites in female cells are often more reactive to lower levels of testosterone . individuals , females and males all have estrogen and testosterone impacting the changing body during puberty , and it is incorrect to View testosterone as a strictly male hormone and estrogen as a strictly female hormone . To understand this process , individuals will need to analyze their specific hormone levels , the

SEX 45 functionality of genes involved in sex differentiation , and environmental stressors and nutrition that may have epigenetic effects on their genes . As a girl reaches puberty , typically the first change that is visible is the development of the breast tissue . This is followed by the growth of axillary and pubic hair . A growth spurt normally starts at approximately age to 11 , and may last two years or more . During this time , a girl height can increase inches a year . The next step in puberty is menarche , the start of menstruation . In boys , the growth of the testes is typically the first physical sign of the beginning of puberty , which is followed by growth and pigmentation of the scrotum and growth of the penis . The next step is the growth of hair , including armpit , pubic , chest , and facial hair . Testosterone stimulates the growth of the larynx and thickening and lengthening of the vocal folds , which causes the voice to drop in pitch . The first fertile typically appear at approximately 15 years of age , but this age can vary widely across individual boys . Unlike the early growth spurt observed in females , the male growth spurt occurs toward the end of puberty , at approximately age 11 to 13 , and a boy height can increase as much as inches a year . In some males , pubertal development can continue through the early . Hormone blockers for transgender individuals are helpful during puberty to prevent the development of inappropriate secondary sex characteristics that may evoke dysphoria . A concern around hormone blockers is that the parent ( or guardian ( are consenting to this treatment on their youth behalf , and some caretakers may not feel comfortable with this process . An ongoing debate exists around whether adolescents are mature and aware enough to advocate for themselves . Pediatricians and advocates who are supportive of prescribing hormone blockers and starting hormone replacement therapy express that transgender identities are often expressed during early childhood and remain consistent across the lifespan , whereas others who are against this process tend to express concern over the weight ofthis decision due to the epigenetic effects of hormone medications that will permanently alter the body and can not be undone if an individual were to no longer identify as transgender . Chromosomes and Hormones , Oh My ! Watch these two videos to gain more insight into the chromosome and hormones . One or more interactive elements has been excluded from this version of the text . You can view them online here on . And One or more interactive elements has been excluded from this version of the text . You can view them online here ?

46 EMERSON WOLFE , Surgery , and Medications is the way in which environmental factors influence the expression of genes . First , let look at reptilian and mammalian studies to explore some epigenetic factors that can influence differences between sexes . According to Forger ( 2016 ) In many reptiles and some fish the ambient temperature during incubation determines the sex ofthe individual . In other words , perfectly good male or female brains and bodies can develop from an identical genome , based on differences in the epigenetic regulation of that genome . Similarly , although there are genetic differences between male and female mammals , many of the sex differences in mammalian brains and behavior are likely epigenetic in origin ( In studies conducted on rodents , such as mice , rats , and guinea pigs who share similarities with human males regarding olfactory cues and some sexual behaviors , researchers have found that the development of the brain is influenced by environmental factors at birth that alter cell death in the brain and the way that sex hormones are processed based on activation or inactivation of key genes depending on the presence of certain ( Forger , 2016 ) One or more interactive elements has been excluded from this version of the text . You can view them online here on . Surgeries The removal of organs , such as gonads , can alter the production of hormones and require an individual to take synthetically produced hormones . Hysterectomy ( removal of the uterus ) orchiectomy ( removal of one or both testes ) and other procedures that alter the reproductive organs or other endocrine glands will alter the natural production of hormones and cause changes to the body . Medications can be prescribed to stand in for the lost hormones that can no longer be created , but medications will require adjusting and tweaking over time which may never completely compare to the original levels previously maintained . Medications Many people associate medically prescribed hormones with transgender individuals who are physically transitioning however , hormone replacement therapy was first developed to help women with symptoms related to menopause ( 2019 ) Additionally , testosterone injections and pills are often advertised to men under the premise that they will provide them with a confidence boost , higher sex drive , more muscle mass , etc . Harvard Health Publishing , 2020 ) Hormones are present in birth control pills , and narcotics and prescribed substances , such as steroids , drugs , chemotherapy and more , can impact the endocrine system in numerous ways which will then impact the way that sex hormones are produced and processed . Thus , these medications beyond hormone replacement therapies can have impacts upon sexual functioning , fat distribution , mood , body hair production and more . Some changes , such as body hair production , may remain even after the medication is stopped .

SEX 47 Female Anatomy Some of the organs involved in female reproduction are in the Figure below . The reproductive structures of the human female are shown . Female reproductive anatomy ( credit a modification of work by Gray Anatomy credit modification of work by ) Female reproductive anatomy includes external structures ( the clitoris and vulva ) structures involved in the production of eggs and in fetal development ( ovaries corpus , and uterus ) and structures involved in the transport of sperm , eggs , and babies ( vagina , cervix and oviduct ) For a useful interactive , check out Interactive Pussy . Image from Pussy We propose a new use of the word . Egg production and fetal development Ovary females have two ovaries that are the site of egg production , and , egg is fertilized , the site of the corpus . The ovary produces hormones estrogen and progesterone and testosterone . Corpus the site of egg maturation within the ovary . After ovulation ( release of the egg ) the corpus produces progesterone to maintain a possible pregnancy . Uterus this , triangular organ is where a fertilized egg implants and develops . This organ develops a thick blood lining and sheds this lining on a monthly cycle . Transport of eggs , sperm , and embryos Vagina a highly expandable pouch structure that serves as the opening of the female reproductive tract to outside the body . The vagina is the point of sperm entry , and the point of exit for unfertilized eggs , menstrual discharge and for babies , if pregnant and having a vaginal delivery . Cervix the opening between the vagina and the uterus . The size of this opening varies from tightly closed to open for the passage of sperm , to open enough for a baby to pass through . sometimes called fallopian tubes ) these ducts transport mature eggs from the ovary toward the uterus . sperm and egg are in the oviduct at the same time , the egg can be fertilized by a sperm .

48 EMERSON WOLFE , Exterior structures Vulva a general term for the exterior parts surrounding the vagina , including the labia and labia , which are the folds on either side of the clitoris , urethra , and vagina . Often this term is overlooked , with folks referring to the vulva as vagina , which is the internal structure . it OK and more accurate to say vulva when referring to the external structure . importantly , the structure and appearance of the vulva may vary widely . There no one size fits all when it comes to the vulva and diversity in appearance needs to be celebrated . Clitoris the sensitive organ that is analogous to the head of the penis . The part ofthe clitoris that is visible outside the body is dorsal to ( closer to the belly ) the urethra and the vagina ) The interior part of the clitoris extends internally along either side of the vagina . I i , A i . urn , Public domain , via Commons Unfortunately , the structure of the clitoris is not well known by many people , including to those folks with a clitoris . Historically ( and even in some contemporary settings ) this feature has been muted or correlated with antiquated notions of female sexuality such as hysteria or neurosis . One or more interactive elements has been excluded from this version of the text . You can view them online here ?

Female reproductive physiology Female reproductive anatomy and physiology has many similarities to that of the male . As described earlier , females also use and secretion from the pituitary triggered by from the hypothalamus to stimulate hormone production by the gonads . There is also negative feedback to regulate hormone production . However , in females , the interplay among the hormonal signals is more complicated than in males . While male hormonal and signaling provide a relatively steady level of the sex hormone testosterone , for females there is a

SEX DIFFERENTIATION 49 monthly cycle over which the circulating hormone levels go up and down at the same time as changes occur in the ovaries and the uterus . This surging of hormones along with the changes in the ovaries and uterus require the more complicated physiological controls described below . Menstruation Sometimes a Taboo Topic The banner in the picture below was carried in a 2014 march in as part of the celebration of Menstrual Hygiene Day . Menstrual Hygiene Day is an awareness day on May 28 of each year that aims to raise awareness worldwide about menstruation and menstrual hygiene . Maintaining good menstrual hygiene is difficult in developing countries like because of taboos on discussing menstruation and lack of availability of menstrual hygiene products . Poor menstrual hygiene , in turn , can lead to embarrassment , degradation , and reproductive health problems in females . May 28 was chosen as Menstrual Hygiene Day because of its symbolism . May is the fifth month of the year , and most women average five days of menstrual bleeding each month . The day was chosen because the menstrual cycle averages about 28 days . World Hygiene Day celebration by The Helping Hand a non organization . The monthly female reproductive cycle can be divided into three phases , the follicular phase , ovulation , and the luteal phase . For each of these phases , there are concurrent changes happening in the uterus and in the ovaries . See the figure below for a diagram of the phases of the female reproductive cycle and what is happening in the ovary , the uterus , and circulating hormone levels . Female hormone cycle .

50 EMERSON WOLFE , is , vu sum ' um . nu . uF Diagram of the menstrual cycle ( based on several sources ) The Follicular Phase The name follicular phase is in reference to the follicle in the ovary that matures during this phase ( note the ovarian histology shown in Figure ) This phase begins on day one ofa female reproductive cycle . Day one is defined as the first day of menstruation ( the first day of a period ) Menstruation occurs for about the first days ofthe follicular phase . During these days , ifa female is not pregnant , low circulating levels of the hormone progesterone trigger the breakdown of the endometrium ( the lining of the uterus ) This tissue exits the uterus through the cervix and then leaves the body out the vagina . During menstruation , low circulating levels of estrogen and progesterone stimulate production ( from the hypothalamus in the brain ) which leads to and secretion by the pituitary gland . signals the maturation of several follicles within the ovaries . These follicle cells produce a steadily increasing amount of estrogen ( note the estradiol ( a type of estrogen ) increases from day in Figure ) Ovulation Ovulation refers to the rupture of a mature follicle within the ovary this ruptured follicle releases an oocyte ( an unfertilized egg ) into the abdominal space . Because this rupture is an actual breakage , some females will feel a twinge or slight pain during ovulation . Ovulation generally happens around day 14 ofthe reproductive cycle in one ovary . Luteal phase During the luteal phase , the now empty follicle within the ovary collapses . This collapsed mass of cells is called a corpus . The corpus produces progesterone that enters the blood circulation . Progesterone signals the hypothalamus to signal the pituitary to reduce and production , which prevents other follicles from maturing . Ifthe oocyte in the oviduct is not fertilized , the corpus degrades , causing a drop in progesterone ,

SEX 51 which triggers the beginning of menstruation and the return to the follicular phase of the reproductive cycle ( back to day after about a cycle ) If the oocyte IS fertilized , then that begins the cellular process of fetal development ( pregnancy ) One or more interactive elements has been excluded from this version of the text . You can view them online here on . Menopause Female fertility ( the ability to conceive ) peaks when women are in their twenties , and is slowly reduced until a women reaches 35 years of age . After that time , fertility declines more rapidly , until it ends completely at the end of menopause . Menopause is the cessation of the menstrual cycle that occurs as a result of the loss of ovarian follicles and the hormones that they produce . A woman is considered to have completed menopause if she has not in a full year . After that point , she is considered . The average age for this change is consistent worldwide at between 50 and 52 years of age , but it can normally occur in a woman forties , or later in her fifties . Poor health , including smoking , can lead to earlier loss of fertility and earlier menopause . INTERSEX ANATOMY About in people will be born noticeably intersex , such as having partial elements of both a penis and vulva . However , other intersex conditions may not show up until later , such as during puberty or when trying to conceive children , making this number higher in actuality . Some estimates show that some intersex conditions can be as high as in 66 . Taken altogether , some researchers , such as Anne , argue that the number of intersex people is actually closer to about in 100 ( intersex Society of North America , Here is a video of individuals sharing some of their experiences One or more interactive elements has been excluded from this version of the text . You can view them online here on . The term intersex is an umbrella term that encompasses many different variations to sex . Some intersex individuals have variations to their sex chromosomes or that the gene on the chromosome is not present or was onto an chromosome . Thus , in some instances , a male can have chromosomes and a female can have XY chromosomes . Other variations are possible as well ( According to with the intersex Society of North America ( The last time I counted , there were at least 30 genes that have been found to have important roles in the development of sex in either humans or mice . Of these 30 or

52 EMERSON WOLFE , so genes are located on the chromosome , on the chromosome and the rest are on other chromosomes , called ( on chromosomes , 10 , 17 , 19 ) In light of this , sex should be considered not a product of our chromosomes , but rather , a product of our total genetic makeup , and of the functions of these genes during development ( para . Therefore , we need to be careful when we oversimplify this process and relate sex to or XY chromosomes only . Male Anatomy Some of the organs involved with male reproduction are below . sigmoid colon bladder pubic bone suspensory ligament of penis puboprostatic ligament perineal membrane seminal vesicle ejaculatory duct prostate gland external urethral sphincter penis corpus anus vas glans penis foreskin urethral opening . testis scrotum Male reproductive anatomy Male reproductive anatomy involves the organs and glands that produce sperm , create semen to transport sperm , and conduct this liquid semen out of the body . Semen production involves the work of accessory glands , each responsible for the production of one or more key ingredients of semen . Male anatomical structures can be broken down into the following Sperm production Testis males typically have two testes ( also called testicles ) which , in humans , descend from the abdomen during fetal development and are enclosed outside the abdomen in the scrotum . Each testis houses many structures ( the seminiferous ) in which sperm are made . Specialized cells ( the cells ) in the testes produce testosterone . Scrotum a pouch of skin that holds the testes that contracts or expands to adjust the distance the testes are from the body to regulate their temperature .

SEX DIFFERENTIATION now of luv our , Dunn in but , I nuts count tun External scrotal view The central raphe on the far left represents the seam where the genital fused in development . In the central image , note the cremaster and dartos muscles , which are important for temperature regulation . On the right , note a deep layer demonstrating the external testes , epididymis , and . Image The Scrotum and Testes by Phil . License Seminiferous these structures within the testes are the actual sites of sperm production ( discussed further below ) Epididymis this rubbery device sits astride the testis . Sperm mature here and are stored prior to ejaculation ( when semen leaves the body , typically during orgasm ) Semen production 53 Seminal these two glands produce an alkaline ( basic ) fluid that can neutralize the acidity of the vagina . This fluid contains fructose and other nutrients to provide energy for the sperm .

54 EMERSON WOLFE , Acrosome Plasma membrane Nucleus Mitochondria . Axial Terminal disc Mid ( connecting ) piece Tail End piece space Cell envelope acrosome Nuclear membrane segment region sheath rin Redundant nuclear Centriole Pie envelope sheath dense . Pair FRONT VIEW Diagram ofhuman sperm , Lad ) Public domain , via Commons ( or ) glands these two glands provide a alkaline fluid that lubricates the inside of the urethra to allow for easier passage of sperm and neutralizes the urethra ( urine residue is acidic ) Some of this fluid exits the penis prior to ejaculation ( this fluid can also contain sperm ) The remainder ofthe fluid combines with the semen ejaculate . Prostate gland this organ wraps around the urethra and provides muscular contractions that help propel semen during ejaculation and block urine flow from the bladder during ejaculation . It also provides fluid in the ejaculate that contains enzymes and zinc that aid in sperm motility .

SEX 55 One or more interactive elements has been excluded from this version of the text . You can view them online here ?

transport Ductus ( or vas ) this pair of tubes carry sperm from the epididymis of each testis into the abdominal cavity where they loop over the bladder and join with the ducts from the seminal to form the ejaculatory ducts . The muscles that line the ductus contract to propel semen during ejaculation . Ejaculatory ducts these ducts are formed by the joining of the vas deference with the duct from the seminal vesicle . Each ejaculatory duct empties into the urethra . Penis the organ that encircles the urethra as the urethra exits the abdomen . This organ changes from flaccid ( soft and limp ) to erect ( rigid and standing away from the body ) during sexual arousal or spontaneously . In uncircumcised men the penis has a fold of skin called a foreskin that during the flaccid state , covers the head of the penis , and during the erect state retracts behind the glans ( or head ) of the penis . I . can , Arterial circulation of the penis image of the penis by Gray anatomy . License Public Domain Urethra the tube that runs from the bladder through the penis through which urine and semen exit the body . Transgender Anatomy Further neurobiological research has been conducted to explain why many transgender people experience gender dysphoria , which is an intense feeling that one sex assigned at birth based on genital presentation does not match the way they feel about themselves . The contrast between the presentation of sex and the brain sex can be explained from a neurobiology perspective by taking a closer look at sex differentiation when we are still in the womb . During prenatal development , sex differentiation of the genitals takes place during

56 EMERSON WOLFE , the first two months of pregnancy while sex differentiation of the brain occurs around months of pregnancy ( 2009 ) This discrepancy between the development of the genitals and the brain has led biological researchers to believe this may be the reason why some individuals are transgender or experience gender dysphoria . Something to keep in mind Humans actually show a lot less sex dimorphism than many other species , which means that there are actually a lot of similarities between men and women , making this type of research rather difficult as differences are often very subtle if present at all . Due to the positive results found with treating some transgender individuals using hormone replacement therapy and hormone blockers in order to bring about desirable changes to the physical body , this adds merit to the perspective that there may be some biological reasons and solutions for people experiencing gender dysphoria from a perspective . Transgender men testosterone therapy will result in enlargement of the clitoris leading to resembling a small penis , facial hair and increased body hair similar to other males in the family , redistribution of body fat and increased muscle mass , deepening of the voice due to testosterone thickening the vocal cords , breast tissue will begin to atrophy , more oily skin , etc . Transgender women Hormone blockers and estrogen hormone therapy will cause breast tissue growth , redistribution of body fat and reduced muscle mass , body hair will thin and grow less fast , penial tissue ( if not having regular sex or masturbating ) will begin to atrophy , the skin will become drier , etc . Electrolysis for hair removal may be desired and voice lessons can help train the individual to speak in a more socially expected female register . Hormone blockers prior to puberty are especially beneficial to prevent these impacts and aid the transition process for transgender individuals . Many parents feel conflicted about this , however , and may not consent on their children behalf to receive these medical services . Surgeries may also be used by some transgender individuals , commonly referred to within these communities as top surgery relating to surgery to either remove or enhance breast tissue or bottom surgery on the genitals . Creating a vagina can be done by utilizing the existing tissue and has promising results for many individuals allowing them to experience sensation , but this will depend on scar tissue . Creating a penis will require the addition of testicular implants and a penial pump for erection purposes . Every transgender person will have to decide what steps they want to take to help them feel as comfortable as possible in their bodies . If someone does not use hormones or have surgeries , it does not make them any less transgender than someone who does . Also , keep in mind that access to healthcare is a privilege and not a right in our country , which can be a barrier for many individuals in receiving the care they need . Family , culture , society , etc . also act as barriers in this process . It is never appropriate to question a transgender person about their genitals , surgeries or hormones , and doing so would be examples of . This is and dehumanizing and reduces transgender individuals to their genitals and body rather than seeing them as a whole person with feelings and the right to privacy . Create a space where someone feels comfortable to share their experiences with you on their own instead rather than questioning them . We will talk more about next week . Until then , here are some resources National Center for Transgender Trans Student Educational Research the Transgender People in Your Life A Guide to Being a Good Ally Additional resources for your reference If you or someone you know is interested in learning more about how hormone replacement therapy impacts the body , check out the links provided by the University of California San Francisco Transgender Care . Transgender Care also has more information on the types of surgeries that are available for transgender individuals . What about when individuals , such as those who identify as , and experience gender dysphoria as well ?

Or , what about when transgender individuals do experience gender dysphoria ?

What might be some biological explanations ?

We need more research ! A question to think about SEX 57 further is a social construct , then does biology even really matter anyway and are researchers trying too hard to find biological answers ?

This goes back to the debate once again . We will discuss gender as a social and cultural phenomenon next week to explore this question further from other perspectives . To hear personal stories and experiences individuals , watch this video One or more interactive elements has been excluded from this version of the text . You can view them online here on . Bodies are Beautiful and Vary So Much The authors of this text ( and Emerson Wolfe ) could not find images that represent transgender bodies , apart from images depicting surgeries , in a respectful way . If you know a transgender , or gender expansive artist who would like to see their work featuring beautiful bodies added to this resource , please share your instructor email with them to reach out for more information on this project . THE OF GENDER THE DEVELOPMENT OF SEX Why do we label different anatomical parts as female anatomy and male anatomy ?

Our understanding of the body is usually through the lens of long deceased researchers and doctors who believed in strict gender binary systems with males having normal bodies and with women being framed as having less capable bodies . The existence of intersex people indicates that the process of sex differentiation is very complex , yet our understanding today even is misguided by an oversimplification of this process that is shaped by our cultural definition of gender and our gender schema ( aka a cognitive blueprint based on your experiences ) Think to your own and explore how this has shaped your concept of sex and gender even today . We will discuss cultural perspectives on gender and how this impacts our idea of biological sex next week . Until then , explore the following questions Do you know your hormone levels ?

Do you know your sex chromosomes ?

Take this moment to normalize the way your genitals looked at birth and how they look currently and recognize that bodies are different and beautiful . Conclusion As you reach the end of this reading , the hope is that you have more questions than answers about the vast possibilities that contribute to your present bodily form and physiological functioning . Human experiences are genetic and environmental , and sex differentiation further showcases how this process is often oversimplified and discussed from within binary systems of female and male when the reality lends itself more toward and from the moment we begin in the womb to how we undergo many changes throughout our course . Use this knowledge to understand your body functioning , and harness this information as you explore what brings you and others sexual pleasure if this connection is something you seek . Use scientific advancements to be allies to the human experience and also recognize the limitations to scientific study . We do not have all the answers and may never , so continue to ask questions about human sexual development , anatomy , and physiology .

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Emma Bryce . 2016 ) What is ?

Carlos . watch ?

Lori . 2017 ) Le clitoris Animated documentary ( 2016 ) by Lori . Glamour . 2016 ) This is your period in minutes Glamour . 2015 ) What it like to be intersex . 2016 ) Trans people talk to their younger selves . watch ?

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Take a breath before you take the plunge . Harvard Men Health Watch . Retrieved from website link . Intersex Society of North America . Does having a chromosome make someone a man ?

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SEX 59 , A . 2009 ) Sexual differentiation of the human brain in relation to gender identity and sexual orientation . Functional Neurology , 24 ( Here is the article if you like to read more . License Introduction to Human Sexuality by Emerson Wolfe is licensed under a Creative Commons International License .