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Lecture 5

Earth Sciences 1086F/G Lecture 5: Chapter 5

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Western University
Earth Sciences
Earth Sciences 1086F/G
Audrey Beauvoir

Chapter 5: Gender Identity and Gender Roles Prenatal Sexual Differentiation Aristotlemistakenly believed thattheanatomicaldifferencebetweenmalesandfemaleswasdue to the heat of semen at the time of sexual relations o Hot semen males; cold semen females A sperm cell fertilizes an ovum 23 chromosomes from male combine 23 chromosomes from females 23 pairs: sex chromosomes zygote (): at this stage, the stamp of a unique individual has been ensured Female: XX sex chromosomal structure; Male: XY sex chromosomal structure After fertilization, the zygote divides repeatedly o Three weeks a primitive heart o 5 / 6 weeks embryo (,) has a pair of sexually undifferentiated gonads o 7 weeks genetic code (XX / XY) begins to assert itself changes in the gonads XY: testes begin to differentiate; seminiferous tubules () o 11 / 12 weeks: XX: ovaries begin to differentiate and form; Sex Hormones and Sexual Differentiation o Male Androgens: male sex hormones Testosterone Fosters development of male sex characteristics Connected with the sex drive Spurs differentiation of male (Wolffian) duct system Dihydrotestosterone(DHT): influence the development of external genitals Mullerian-inhibiting substance(MIS): avoid to develop female duct system o Female Small amount of androgen produced in female fetuses() Mullerian ducts evolve into fallopian tubes, uterus, upper 2/3 of the vagina Female sex hormones are not involved in fetal sexual differentiation Descent of the Testes and Ovaries o 10 weeks: they are almost even with the upper edge of the pelvis Ovaries remain there for the rest of the prenatal period o 4 months: testesscrotal sac through the inguinal canal(), which then closes o Cryptorchidism() Sex Chromosome Abnormalities o Klinefelters syndrome: condition that affects about one in 500 males Give an extra X sex chromosome XXY Men fail to develop appropriate secondary sex characteristics infertile o Turners syndrome: condition that affect about one in 2500 females Having only one X sex chromosome Females may not naturally undergo puberty need hormone treatment o Brain, like the genital organs, undergoes prenatal sexual differentiation Gender Identity A persons internal psychological sense of being male, female, or any other shade of gender Assigned sex: the classification of anatomic sex given at birth as either male, female, intersex Most people are cisgender: gender identity that matches assigned sex Most children (18 months): aware of their assigned sex Most children (36 months): acquired a firm sense of gender identity Nature and Nuture o Gender identity is usually consistent with chromosomal gender o In western culture, societal rigidity gender binary (strictly either male / female) Represents a socially prescribed way of classifying gender in our culture Does not accurately reflect the diverse range of gender identities actually exist o Intersex individuals who possess() the gonads of one anatomic sex and external genitalia() that are ambiguous or typical of the other anatomic sex Less rare (one in 5000); have testes or ovaries, but not both Gonads match their chromosomal sex o Hermaphrodite: identities & roles of the genders-assigned at birthQuite rare o Congenital adrenal hyperplasia (CAH) Most common female intersex condition XX female: female internal sexual structures and male external genitals Caused by high levels of androgens Female with CAH Showed more interest in masculine-typed toys More likely to have boys as playmates and want male-typed careers o Androgen insensitivity syndrome XY males have experienced lower-than-normal prenatal sensitivity to androgens External genitals are feminized o Dominican republic syndrome: Genetic enzyme disorder Prevents testosterone from masculin
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