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Chapter 10

Thorough Notes on Chapter 10

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Janelle Leboutillier

Physio Chapter 10 Sexual Behaviour Children begin to prefer sex-typed toys between the ages of 12 and 18 months. At these same ages, children are unable to match sex-typed toys (vehicles and dolls) with male or female faces or voices, suggesting that they have not yet been socialized to think of toys as male or female Sexual Development Aristotle argued that the sex of a child was the result of the temperature of semen at the time of conception. Hot semen resulted in males, and cool semen resulted in females. Sex ChromosomeAbnormalities Turner's syndrome: child receives only a single X chromosome (XO) 1 2500 live births Asingle X chromosome carries sufficient genetic material to produce an individual who is quite normal in many ways. However, the lack of a second sex chromosome does have an impact on fertility, growth, and hormone production and is associated with higher risk of diabetes, osteoporosis, and cardiovascular disease normal female external genitalia, but the ovaries develop abnormally the ovaries do not produce either ova or normal levels of female hormones, leading to inability to produce normal hormone levels (eggs) = infertility Intelligence is normal, but specific deficits in spatial relationships and memory can occur Klinefelter Syndrome: features an XXY genotype. Individuals are male, but they usually experience reduced fertility and require hormone treatment at puberty to promote the development of secondary male sex characteristics (facial hair, deeper voice, development of external genitalia) and to inhibit female characteristics such as breast development is one of the most common genetic abnormalities related to the sex chromosomes, occurring in 1.79 out of 1,000 male births normal intelligence, but mild cognitive difficulties (delayed and reduced verbal skills) and social awkwardness XYY: 1 out of 1,000 male births The physical and behavioral correlates of the condition are typically subtle and generally do not prompt the parents to seek a postnatal genetic analysis The boys appear to be physically within typical limits, although they tend to be somewhat taller and leaner, suffer from acne, and have a higher risk for minor physical abnormalities of the eye, elbow, and chest Average IQ scores are slightly below the average of males with normal XY genotypes Men with the XYY genotype are fertile, but they are slightly more likely than typical men to produce sperm with sex chromosome abnormalities The popular press immediately embraced the hypothesis that an extra Y chromosome would produce a violent super male. - This was false the majority of the criminal behavior of the XYY men involved property crimes rather than violent crimes. In comparison to genetic abnormalities like Down syndrome, abnormalities due to a third sex chromosome appear to have relatively mild effects a study of more than 13,000 newborns over a 13-year period, found that none of the children with three sex chromosomes were mentally retarded and that all were in regular public school. no increases in criminal activity, mental disorders, or physical disorders relative to the population with typical sex chromosomes Three Stages of Prenatal Development Male and female structural development involves three distinct processes: the development of gonads, of internal organs, and of external genitalia. In the majority of cases, all three processes occur congruently to produce an unambiguous male or female. In a rare condition known as intersex, elements of both male and female development occur in the same fetus. The Development of Gonads both male and female fetuses have identical primordial gonads that have the capacity to develop into either ovaries, the female gonads, or testes, the male gonads. At about six weeks after conception, a gene on the short arm of the Y chromosome, known as the sex-determining region of the Y chromosome, or SRY, is expressed in male embryos Testis- determining factor, the protein encoded by the SRY gene, switches on additional genes that cause the gonads to develop into testes. In female embryos, which lack the SRY gene and its ability to produce testis-determining factor, alternate genes guide the development of the primordial gonad into ovaries Male mice genetically modified to lack the SRY gene develop ovaries, whereas female mice in which the SRY gene has been inserted develop testes Differentiation of the Internal Organs The differentiation of the internal organs, follows the development of the gonads Until about the third month of development in humans, both male and female fetuses possess a male Wolffian system and a female Mllerian system. In males, the Wolffian system will develop into the seminal vesicles, the vas deferens, and the prostate. In females, the Mllerian system will develop into the uterus, the upper portion of the vagina, and the fallopian tubes During the third month, the males relatively new testes begin to secrete two hormones, testosterone and anti-Mllerian hormone Testosterone, one of several types of male hormone or androgen, promotes the development of the Wolffian system. Anti-Mllerian hormone initiates the degeneration of the Mllerian system. In the female fetus, no additional hormones are needed for development. Unlike the testes, the ovaries are not active during fetal development. In the absence of any androgens or anti-Mllerian hormone, the Mllerian system will develop in the typical female direction. Nonfunctional remnants of the Wolffian system remain throughout a womans life. Androgen insensitivity syndrome (AIS) disrupts the normal development of the Wolffian system in males a defective gene produces abnormal androgen receptors .As a result, the fetuss tissues are blind to the presence of androgens. Fetuses with AIS have an XY genotype and normal testes. The testes release androgens and anti-Mllerian hormone in a normal manner, but the lack of functional androgen receptors prevents the development of the Wolffian system. However, anti-Mllerian hormone still works normally, so the female Mllerian system also fails to develop. Because the Mllerian system is responsible for the upper two thirds of the vagina, the result is a shallow vagina and no ovaries, fallopian tubes, or uterus. Although adult individuals withAIS are infertile, their external appearance is quite typically female, Individuals with AIS are genetic males but typically have female appearance and strong female gender identities Development of the External Genitalia The development of the external genitalia follows the differentiation of the gonads during the sixth week after conception. The male external genitalia include the penis and scrotum. The female external genitalia include the labia, clitoris, and outer part of the vagina. No hormonal activity is required in order to develop female external genitalia. However, hormonal stimulation is essential for the development of male external genitalia Aparticul
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