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Encyclopedia > Sexual differentiation
See sex differences in humans for permanent sex differences.

Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote (fertilized egg). As male and female individuals develop from zygotes into fetuses, into infants, children, adolescents, and eventually into adults, sex and gender differences at many levels develop: genes, chromosomes, gonads, hormones, anatomy, psyche, and social behaviors. Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ... This article is about biological sex differences. ... This article is about the Male sex. ... For other uses, see Female (disambiguation). ... It has been suggested that Biparental zygote be merged into this article or section. ... Categories: Biology stubs ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... For other uses, see Fetus (disambiguation). ... This article or section does not cite its references or sources. ... Gender in common usage refers to the sexual distinction between male and female. ... For other uses, see Gene (disambiguation). ... A scheme of a condensed (metaphase) chromosome. ... The gonad is the organ that makes gametes. ... For other uses, see Hormone (disambiguation). ... Human heart and lungs, from an older edition of Grays Anatomy. ... This article does not cite any references or sources. ...


Sex differences range from nearly absolute to simply statistical. Sex-dichotomous differences are developments which are wholly characteristic of one sex only. Examples of sex-dichotomous differences include aspects of the sex-specific genital organs such as ovaries, a uterus or a phallic urethra. In contrast, sex-dimorphic differences are matters of degree (e.g., size of phallus). Some of these (e.g., stature, behaviors) are mainly statistical, with much overlap between male and female populations. A sex difference is a distinction of biological and/or physiological characteristics typically associated with either males or females of a species in general. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... This article is about female reproductive anatomy. ... In anatomy, the urethra is a tube which connects the urinary bladder to the outside of the body. ... Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ... This article is about the symbol of the erect penis. ... Height is the measurement of distance between a specified point and a corresponding plane of reference. ...


Nevertheless, even the sex-dichotomous differences are not absolute in the human population, and there are individuals who are exceptions (e.g., males with a uterus, or females with an XY karyotype), or who exhibit biological and/or behavioral characteristics of both sexes. The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila) and some plants (Ginkgo). ... Karyogram of human male using Giemsa staining. ...


Sex differences may be induced by specific genes, by hormones, by anatomy, or by social learning. Some of the differences are entirely physical (e.g., presence of a uterus) and some differences are just as obviously purely a matter of social learning and custom (e.g., relative hair length). Many differences, though, such as gender identity, appear to be influenced by both biological and social factors ("nature" and "nurture"). This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Hormone is also the NATO reporting name for the Soviet/Russian Kamov Ka-25 military helicopter. ... Human heart and lungs, from an older edition of Grays Anatomy. ... Observational learning or social learning refers to learning that occurs as a function of observing, retaining and replicating behaviour observed in others. ... This does not cite any references or sources. ... The nature versus nurture debates concern the relative importance of an individuals innate qualities (nature) versus personal experiences (nurture) in determining or causing individual differences in physical and behavioral traits. ...


The early stages of human differentiation appear to be quite similar to the same biological processes in other mammals and the interaction of genes, hormones and body structures is fairly well understood. In the first weeks of life, a fetus has no anatomic or hormonal sex, and only a karyotype distinguishes male from female. Specific genes induce gonadal differences, which produce hormonal differences, which cause anatomic differences, leading to psychological and behavioral differences, some of which are innate and some induced by the social environment. For other uses, see Fetus (disambiguation). ... This article or section does not cite its references or sources. ... Karyogram of human male using Giemsa staining. ... The gonad is the organ that makes gametes. ... For other uses, see Society (disambiguation). ...


The various ways that genes, hormones, and upbringing affect different human behaviors and mental traits are difficult to test experimentally and charged with political conflict.

Contents

Chromosomal sex differences

Humans have forty-six chromosomes, including two sex chromosomes, XX in females and XY in males. It is obvious that the Y chromosome must carry at least one essential gene which determines testicular formation (originally termed TDF). A gene in the sex-determining region of the short arm of the Y, now referred to as SRY, has been found to direct production of a protein which binds to DNA, inducing differentiation of cells derived from the genital ridges into testes. In transgenic XX mice (and some human XX males), SRY alone is sufficient to induce male differentiation. The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila) and some plants (Ginkgo). ... The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila) and some plants (Ginkgo). ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... This article is about the SRY gene. ... XX male syndrome (also called de la Chapelle syndrome) is a rare sex chromosomal disorder in men. ...


Investigation of other cases of human sex reversal (XX males, XY females) has led to discovery of other genes crucial to testicular differentiation on autosomes (e.g., WT-1, SOX9, SF-1), and the short arm of X (DSS). XX male syndrome (also called de la Chapelle syndrome) is a rare sex chromosomal disorder in men. ... Swyer syndrome, or XY gonadal dysgenesis, is a type of female hypogonadism in which no functional gonads are present to induce puberty in an otherwise normal girl whose karyotype is then found to be XY. Her gonads are found to be nonfunctional streaks. ... An autosome is a non-sex chromosome. ...


Gonadal differentiation

Early in fetal life, germ cells migrate from structures known as yolk sacs to the genital ridge. By week 6, undifferentiated gonads consist of germ cells, supporting cells, and steroidogenic cells. A germ cell is part of the germline and is involved in the reproduction of organisms. ... In embryology, the gonadal ridge (or genital ridge) is the precursor to the gonads. ... The gonad is the organ that makes gametes. ... A germ cell is part of the germline and is involved in the reproduction of organisms. ...


In a male, SRY and other genes induce differentiation of supporting cells into Sertoli cells and (indirectly) steroidogenic cells into Leydig cells to form testes, which become microscopically identifiable and begin to produce hormones by week 8. Germ cells become spermatogonia. A Sertoli cell (a kind of sustentacular cell) is a nurse cell of the testes which is part of a seminiferous tubule. ... Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testes. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... A Spermatogonium (plural: spermatogonia) is an intermediary male gametogonium (a kind of germ cell) in the production of spermatozoa. ...


Without SRY, ovaries form during months 2-6. Failure of ovarian development in 45,X girls (Turner syndrome) implies that two functional copies of several Xp and Xq genes are needed. Germ cells become ovarian follicles. Supporting and steroidogenic cells become theca cells and granulosa cells, respectively. // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... ‹ The template below (Expand) is being considered for deletion. ... ‹ The template below (Expand) is being considered for deletion. ... Ovarian follicles or Graafian follicles (after Regnier de Graaf) are the roughly spherical cell aggregations in the ovary containing an ovum and from which the egg is released during ovulation. ... The theca folliculi comprise a layer of the ovarian follicles. ... A granulosa cell is a supporting cell for the developing female gamete in the ovary of mammals. ...


Hormonal differentiation

In a male fetus, testes produce steroid and protein hormones essential for internal and external anatomic differentiation. Leydig cells begin to make testosterone by the end of month 2 of gestation. From then on, male fetuses have higher levels of androgens in their systemic blood than females. The difference is even greater in pelvic and genital tissues. Antimullerian hormone (AMH) is a protein hormone produced by Sertoli cells from the 8th week on. AMH suppresses development of müllerian ducts in males, preventing development of a uterus. Steroid hormones are steroids which act as hormones. ... Hormone is also the NATO reporting name for the Soviet/Russian Kamov Ka-25 military helicopter. ... Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testes. ... Testosterone is a steroid hormone from the androgen group. ... Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... Antimullerian hormone is a protein hormone produced by human and other mammalian gonads. ... A Sertoli cell (a kind of sustentacular cell) is a nurse cell of the testes which is part of a seminiferous tubule. ... The Müllerian ducts are paired ducts of the embryo which empty into the cloaca, and which in the female develop into the upper vagina, cervix, uterus and oviducts; in the male they disappear except for the vestigial vagina masculina and the appendix testis. ... This article is about female reproductive anatomy. ...


Fetal ovaries produce estradiol, which supports follicular maturation but plays little part in other aspects of prenatal sexual differentiation, as maternal estrogen floods fetuses of both sexes. Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ...


Genital differentiation

A differentiation of the sex organ can be seen. However, this is only the external genital differentiation. There is also an internal genital differentiation. In prenatal development, the urinary and reproductive organs are developed from the intermediate mesoderm. ... A sex organ, or primary sexual characteristic, as narrowly defined, is any of those anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; in mammals, these are: Female: Bartholins glands, cervix, clitoris, Fallopian tubes, labia, ovaries, Skenes...


Internal genital differentiation

Gonads are histologically distinguishable by 6-8 weeks of gestation. A fetus of that age has both mesonephric (wolffian) and paramesonephric (mullerian) ducts. Subsequent development of one set and degeneration of the other depends on the presence or absence of two testicular hormones: testosterone and AMH. Disruption of typical development may result in the development of both, or neither, duct system, which may produce morphologically intersexual individuals. The gonad is the organ that makes gametes. ... The Wolffian duct (also known as archinephric duct, Leydigs duct, and the mesonephric duct) is an paired organ found in mammals including humans during embryogenesis. ... The Müllerian ducts are paired ducts of the embryo which empty into the cloaca, and which in the female develop into the upper vagina, cervix, uterus and oviducts; in the male they disappear except for the vestigial vagina masculina and the appendix testis. ... Testosterone is a steroid hormone from the androgen group. ... Antimullerian hormone is a protein hormone produced by human and other mammalian gonads. ... An intersexual or intersex person (or animal of any unisexual species) is one who is born with genitalia and/or secondary sexual characteristics of indeterminate sex, or which combine features of both sexes. ...


Local testosterone causes each wolffian duct to develop into epididymis, vas deferens, and seminal vesicles. Without male testosterone levels, wolffian ducts degenerate and disappear. Müllerian ducts develop into a uterus, fallopian tubes, and upper vagina unless AMH induces degeneration. The presence of a uterus is stronger evidence of absence of testes than the state of the external genitalia. Male Anatomy The epididymis is part of the human male reproductive system and is present in all male mammals. ... The vas deferens (plural: vasa deferentia), also called ductus deferens, (Latin: carrying-away vessel) is part of the male anatomy of some species, including humans. ... Categories: Stub | Andrology | Exocrine system | Reproductive system ... This article is about female reproductive anatomy. ... The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges (singular salpinx) are two very fine tubes leading from the ovaries of female mammals into the uterus. ... The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis...


External genital differentiation

For illustrations, see the External links section.


By 7 weeks, a fetus has a genital tubercle, urogenital groove and sinus, and labioscrotal folds. In females, without excess androgens, these become the clitoris, urethra and vagina, and labia. A genital tubercle is a body of tissue which forms in the ventral, caudal region of mammalian embryos of both sexes, and eventually develops into a phallus. ... The labioscrotal folds (or labioscrotal swellings) are paired embryonic structures that represent the final stage of development of the caudal end of the external genitals before sexual differentiation. ... The clitoris is a sexual organ that is present in biologically female mammals. ... In anatomy, the urethra is a tube which connects the urinary bladder to the outside of the body. ... The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ...


Males become externally distinct between 8 and 12 weeks, as androgens enlarge the phallus and cause the urogenital groove and sinus to fuse in the midline, producing an unambiguous penis with a phallic urethra, and a thinned, rugated scrotum. The penis (plural penises, penes) is an external male sexual organ. ... In some male mammals, the scrotum is a protuberance of skin and muscle containing the testicles. ...


A sufficient amount of any androgen can cause external masculinization. The most potent is dihydrotestosterone (DHT), generated from testosterone in skin and genital tissue by the action of 5α-reductase. A male fetus may be incompletely masculinized if this enzyme is deficient. In some diseases and circumstances, other androgens may be present in high enough concentrations to cause partial or (rarely) complete masculinization of the external genitalia of a genetically female fetus. In biology and medicine, virilization refers to the development of changes which make a male body different from a female body. ... For other uses, see DHT (disambiguation). ... It has been suggested that this article or section be merged with Guevedoche. ... This article is about the medical term. ...


Further sex differentiation of the external genitalia occurs at puberty, when androgen levels again become disparate. Male levels of testosterone directly induce growth of the penis, and indirectly (via DHT) the prostate. Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... The prostate is a compound tubuloalveolar exocrine gland of the male mammalian reproductive system. ...


Breast differentiation

Visible differentiation occurs at puberty, when estradiol and other hormones cause breasts to develop in girls. However, fetal or neonatal androgens may modulate later breast development by reducing the capacity of breast tissue to respond to later estrogen. Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ... For other uses, see Breast (disambiguation). ... Estriol. ...


Hair differentiation

The amount and distribution of body hair differs between the sexes. Males have more terminal hair, especially on the face, chest, abdomen and back, and females have more vellus hair, which is less visible. This may also be linked to neoteny in humans, as vellus hair is a juvenile characteristic. For the 1968 stage production, see Hair (musical), for the 1979 film, see Hair (film). ... Developed hair, which is generally longer, coarser, thicker, and darker than vellus hair. ... One kind of modern beard. ... The term chest hair is generally used to describe hair that grows on the chest of human males, in the region between the neck and the abdomen. ... The term abdominal hair refers to the hair that grows on the abdomen (belly) of humans and non-human mammals, in the region between the pubic area and the thorax (chest). ... Vellus hair is short, fine, peach fuzz body hair. ... Neoteny describes a process by which paedomorphism is achieved, and is a subject studied in the field of developmental biology. ... Vellus hair is short, fine, peach fuzz body hair. ... A separate article is about the punk band called The Adolescents. ...


Other body differentiation

The differentiation of other parts of the body than the sex organ creates the secondary sex characteristics. A sex organ, or primary sexual characteristic, as narrowly defined, is any of those anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; in mammals, these are: Female: Bartholins glands, cervix, clitoris, Fallopian tubes, labia, ovaries, Skenes... A peacock displays his long, colored feathers, an example of his secondary sexual characteristics. ...


General habitus and shape of body and face, as well as sex hormone levels, are similar in prepubertal boys and girls. As puberty progresses and sex hormone levels rise, obvious differences appear. Sex hormones are hormones that affect the reproductive system. ...


In males, testosterone directly increases size and mass of muscles, vocal cords, and bones, enhancing strength, deepening the voice, and changing the shape of the face and skeleton. Converted into DHT in the skin, it accelerates growth of androgen-responsive facial and body hair. Taller stature is largely a result of later puberty and slower epiphyseal fusion. Laryngoscopic view of the vocal folds. ... This article is about the skeletal organs. ... The word epiphysis can mean: The pineal gland, one of the endocrine glands. ...


In females, in addition to breast differentiation, estrogen also widens the pelvis and increases the amount of body fat in hips, thighs, buttocks, and breasts. Estrogen also induces growth of the uterus, proliferation of the endometrium, and menses. The pelvis (pl. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... The endometrium is the inner membrane of the mammalian uterus. ... Menstrual cycle The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes. ...


The difference in adult masculine and feminine faces is largely a result of heavier jaw and jaw muscle development induced by testosterone in late adolescence. Masculine features on average are slightly thicker and coarser. Androgen-induced recession of the male hairline accentuates these differences by middle adult life.


Sexual dimorphism of skeletal structure develops during childhood, and becomes more pronounced at adolescence. Sexual orientation has been demonstrated to correlate with skeletal characters that become dimorphic during early childhood (such as arm length to stature ratio) but not with characters that become dimorphic during puberty (such as shoulder width) (Martin & Nguyen, 2004).


Brain differentiation

In most animals, differences of exposure of a fetal or infant brain to sex hormones produce significant and irreversible differences of brain structure and function which correlate with adult reproductive behavior. This seems to be the case in humans as well; sex hormone levels in male and female fetuses and infants differ, and both androgen receptors and estrogen receptors have been identified in brains. Several sex-specific genes not dependent on sex steroids are expressed differently in male and female human brains. Structural sex differences begin to be recognizable by 2 years of age, and in adult men and women include size and shape of corpus callosum and certain hypothalamic nuclei, and the gonadotropin feedback response to estradiol. Human brain In animals, the brain (enkephale) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ... The androgen receptor is an intracellular steroid receptor that specifically binds testosterone and dihydrotestosterone. ... The corpus callosum is a structure of the mammalian brain in the longitudal fissure that connects the left and right cerebral hemispheres. ... The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ...


Psychological and behavioral differentiation

Human adults and children show many psychological and behavioral sex differences, both dichotomous and dimorphic. Some (e.g., dress) are learned and obviously cultural. Others are demonstrable across cultures and may have both biological and learned determinants. For example, girls are, on average, more verbally fluent than boys, but males, on average, are better at spatial calculation. Because we cannot explore hormonal influences on human behavior experimentally, and because potential political implications are so unwelcome to many factions of society, the relative contributions of biological factors and learning to human psychological and behavioral sex differences (especially gender identity, role, and orientation) remain unsettled and controversial. Sexual orientation refers to the direction of an individuals sexuality, usually conceived of as classifiable according to the sex or gender of the persons whom the individual finds sexually attractive. ...


Current theories of mechanisms of sexual differentiation of brain and behaviors in humans are based primarily on three sources of evidence: animal research involving manipulation of hormones in early life, observation of outcomes of small numbers of individuals with disorders of sexual development (intersex conditions or cases of early sex reassignment), and statistical distribution of traits in populations (e.g., rates of homosexuality in twins). Many of these cases suggest some genetic or hormonal effect on sex differentiation of behavior and mental traits[1]; others do not[citation needed]. An intersexual is a person (or individual of any unisexual species) who is born with genitalia and/or secondary sexual characteristics of indeterminate sex, or which combine features of both sexes. ... Sex assignment refers to the assigning of sex at the birth of a baby. ...


In addition to affecting development, changing hormone levels affect certain behaviors or traits that are gender dimorphic, such as superior verbal fluency among women.[2].


In most mammalian species, and in other hominid species, females are more oriented toward child rearing and males toward competition with other males. Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... A hominid is any member of the biological family Hominidae (the great apes), including the extinct and extant humans, chimpanzees, gorillas, and orangutans. ...


Biology of gender

Main article: Biology of gender

Biology of gender is the scientific analysis of the physical basis for behavioural differences between men and women. It deals with gender identity, gender roles and sexual orientation. Human Brain The biology of gender is the physical basis for behavioural differences between men and women. ... This does not cite any references or sources. ... A bagpiper in military uniform. ... Sexual orientation refers to the direction of an individuals sexuality, usually conceived of as classifiable according to the sex or gender of the persons whom the individual finds sexually attractive. ...


Defeminization and masculinization

Main article: Defeminization and masculinization

Defeminization and masculinization are the processes that a fetus goes through to become a male in sexual differentiation. In this perspective, the female is the default path for a developing human being, was it not for intervening factors that alter the path to the male one. Defeminization is a term in developmental biology, especially zoology, referring to an aspect of the process of sexual differentiation by which a potential female-specific structure, function, or behavior is prevented from developing by one of the processes of male development. ... In biology and medicine, virilization refers to the development of changes which make a male body different from a female body. ...


Biologically, this perspective is supported by that there is neither corresponding female genes nor female hormones to the ones that are active in males only. Estrogen, for instance, is present in both male and female fetuses.


See also

In biology and medicine, virilization refers to the development of changes which make a male body different from a female body. ... Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ... This article is about biological sex differences. ... The List of homologues of the human reproductive system shows how indifferent embryonic organs differentiate into the respective sex organs in males and females. ... Gender in common usage refers to the sexual distinction between male and female. ... A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ... The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila) and some plants (Ginkgo). ... The X0 sex-determination system is a system that grasshoppers, crickets, roaches, and some other insects use to determine the sex of their offspring. ... The ZW sex-determination system is a system that birds, some fishes, and some insects (including butterflies and moths) use to determine the sex of their offspring. ... The Haplo-diploid sex-determination system is a system that most species of bees and ants use to determine the sex of their offspring. ... This article or section is in need of attention from an expert on the subject. ...

References

  1. ^ Pinker, Steven. The Blank Slate. New York: Penguin. 2002. pages 346-350
  2. ^ Pinker, Steven. The Blank Slate. New York: Penguin. 2002. pages 347-348
  • Baum MJ. Mammalian animal models of psychosexual differentiation: When is

‘translation’ to the human situation possible? (2007)Hormones and Behavior 50:579–88. Steven Pinker Steven Arthur Pinker (born September 18, 1954) is a prominent Canadian-born American experimental psychologist, cognitive scientist, and popular science writer known for his spirited and wide-ranging advocacy of evolutionary psychology and the computational theory of mind. ... The Blank Slate: The Modern Denial of Human Nature is a 2002 book (published by Penguin Putnam, ISBN 0670031518) by Steven Pinker arguing against tabula rasa models of psychology, claiming that the human mind is shaped by evolutionary psychological adaptations. ... Steven Pinker Steven Arthur Pinker (born September 18, 1954) is a prominent Canadian-born American experimental psychologist, cognitive scientist, and popular science writer known for his spirited and wide-ranging advocacy of evolutionary psychology and the computational theory of mind. ... The Blank Slate: The Modern Denial of Human Nature is a 2002 book (published by Penguin Putnam, ISBN 0670031518) by Steven Pinker arguing against tabula rasa models of psychology, claiming that the human mind is shaped by evolutionary psychological adaptations. ...

  • Crouch RA. Betwixt and between: the past and future of intersexuality. J Clin Ethics 9:372-384.

Hughes IA, Houk C, Ahmed SF, Lee PA, LWPES/ESPE Consensus Group. (2006) Consensus statement on management of intersex disorders. Arch Dis Childhood.

  • Martin, J. T. and Nguyen, D. H. (2004). Anthropometric analysis of homosexuals and heterosexuals: implications for early hormone exposure. Hormones and Behavior 45. 31-39.
  • Phoenix, C.H., Goy, R.W., Gerall, A.A. and Young, W.C. (1978). Organizing action of prenatally administered testosterone propionate on the tissues mediating mating behavior in the female guinea pig. Endocrinology 65, 369-382.
  • Wallen, K. (2005) Hormonal influences on sexually differentiated behavior in nonhuman primates. Frontiers in Neuroendocrinology 26, 7-26.
  • Wilson BE, Reiner WE. (1998) Management of intersex: a changing paradigm. J Clin Ethics 9:360-9.

External links

Human Physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. ... Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. ... Sexual reproduction is a union that results in increasing genetic diversity of the offspring. ... A pictorial illustration of the human female reproductive system. ... The male reproductive system is a series of organs located outside of the body and around the pelvic region of a male. ... The human females reproductive system. ... Menstrual cycle The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes. ... The estrous cycle (also oestrous cycle; originally derived from Latin oestrus) comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. ... Not to be confused with Mensuration. ... Menstrual cycle The follicular phase (or proliferative phase) is the phase of the estrous cycle, (or, in humans and great apes, the menstrual cycle) during which follicles in the ovary mature. ... Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. ... The luteal phase is the latter phase of the estrous cycle in animals. ... Gametogenesis is the creation of gametes by meiotic division of gametocytes into various gametes. ... Cross section of the epithelium of a seminiferous tubule showing various stages of spermatocyte development Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. ... A Spermatogonium (plural: spermatogonia) is an intermediary male gametogonium (a kind of germ cell) in the production of spermatozoa. ... Spermatogenesis refers to the creation, or genesis, of sperm cells, which occurs in the male gonads or testes. ... The term spermatid refers to the haploid male germ cell that results from secondary spermatocyte division. ... For other uses, see Sperm (disambiguation). ... Oogenesis or rarely oögenesis is the creation of an ovum (egg cell). ... An oogonium is a female gametogonium. ... An oocyte or ovocyte is a female gametocyte or germ cell involved in reproduction. ... An ootid is a female gametid, as opposed to a male spermatid. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... A germ cell is part of the germline and is involved in the reproduction of organisms. ... A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ... This article is about sexual practices (i. ... It has been suggested that Duration of sexual intercourse be merged into this article or section. ... This article is about human physiological erection. ... Ejaculation is the ejecting of semen from the penis, and is usually accompanied by orgasm. ... // An orgasm (sexual climax) is the conclusion of the plateau phase of the sexual response cycle, and is experienced by both males and females. ... Insemination is the introduction of semen into the genital tract of a female. ... This article is about fertilisation in animals and plants. ... Fertility is the natural capability of giving life. ... Masturbation is the manual excitation of the sexual organs, most often to the point of orgasm. ... This article is about human pregnancy in biological females. ... This article does not cite any references or sources. ... This article is about prenatal development in humans. ... Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ... Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ... Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands. ... Graph showing increased risk of Down Syndrome over time The maternal age effect describes the exponentially increasing risks of chromosomal abnormalities as a prospective mother ages. ... The paternal age effect describes the influence that a fathers age has on the chances of conferring a genetic defect to his offspring. ... Menopause is the physiological cessation of menstrual cycles associated with advancing age in women. ... Andropause is a medical phenomenon, similar to the female menopause, that can affect men between the ages of 40 and 55. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. ... Ovoviviparous animals develop within eggs that remain within the mothers body up until they hatch or are about to hatch. ... Poa alpina, a grass which shows vivipary: the seeds germinate while still attached to the mother plant. ... Reproductive endocrinology (RE) is a medical subspecialty that addresses hormonal functioning as it pertains to reproduction. ... The hypothalamic-pituitary-gonadal axis (also HPTA) is a way of referring to the combined effects of the hypothalamus, pituitary gland, and gonads as if these individual endocrine glands were a single entity. ... Andrology (from the Greek andros, man) is the medical specialty that deals with male health, particularly relating to the problems of the male reproductive system and urological problems that are unique to men. ... For other uses, see Hormone (disambiguation). ...

 
 

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