Chapter 10I. sexual development (Text p. 298)A. Background (Video, text p. 299)1. Sexually dimorphic behaviors differ in males and females2. Sex refers to genetic or physiological characteristics3. Gender refers to socially-influenced identity, role and/or behavior4. Intersex refers to combinations of biologically male and female characteristicsB. Production of Gametes and Fertilization1. Gametesa. Ova and spermb. Contain single set of chromosomes (which usually come in a pair)2. Sex chromosomes: X and Ya. Father’s sperm carries either X or Yb. Control the development of glands that will produce sex hormones3. Genetic sex (p. 299)a. XX = femaleb. XY = maleC. Development of the Sex Organs1. Categoriesa. Gonads: testes or ovariesi.Develop firstii.Produce gametes and hormonesiii.Gonad is undifferentiated at 6th weekiv.SRYa.Sex-determining region Yb.On Y-chromosomec.Causes gonad to become a testisv.Without SRY, gonad develops into ovaryvi.Hormonal effectsa.Organizational: alter developmentb.Activational: occurs in developed organismb. Internal sex organs (p. 300)i.All embryos have precursors to male and female internal organs
a.Müllerian system1.Precursor to female structures2.Develop in absence of hormonesb.Wolffian system1.Precursor to male structures2.Needs hormone to developii.Testicular hormonesa.Anti-Müllerian hormone1.Defeminizing effectb.Androgens1.Masculinizing effect2.Testosterone: from testis3.Dihydrotestosteronea.Made from testosterone by 5-reductaseαiii.Disordersa.Androgen insensitivity syndrome1.Androgen receptors don’t work2.Androgens can’t masculinize; no Wolffian development3.Anti-Müllerian hormone still works; no Müllerian development4.External genitalia are female but reproduction is not possibleb.Persistent Müllerian duct syndrome1.Two causesa.No anti-Müllerian hormoneb.No receptor for anti-Müllerian hormone2.In males, androgens masculinize, but defeminization fails3.Born with male and female internal sex organsc.Turner syndrome1.XO2.No Y, therefore no testis3.Need two X chromosomes for ovary, therefore no ovary4.Not accurate—women with Turner’s syndrome can have ovaries and, in fact, can be fertilec.External genitalia (p. 302)i.No hormone = femaleii.Dihydrotestosterone = male
D. Sexual Maturation1. Sex characteristicsa. Primary: gonads, internal sex organs, external genitaliab. Secondary: enlarged breasts, widened hips, beard, deep voice2. Pubertya. Hypothalamus secretes gonadotropin-releasing hormone (GnRH) (p. 302) (p. 303)i.Stimulates production of release of gonadotropic hormonesa.Luteinizng hormone (LH)b.Follicle stimulating hormone (FSH)ii.GnRH also under control of kisspeptin (a peptide)a.Kisspeptin produced in arcuate nucleus of hypothalamusb.Leptinc.Released by fat cellsii.Accelerates pubertya.Acts on receptors found on kisspeptin-secreting neurons in arcuate nucleusiii.Suppresses appetitec.Steroid sex hormones (Table 10.1, text p. 303)d.Gonadotropins stimulate releaseii.Ovaries produce estrogens such as estradioliii.