SEXUAL DEVELOPMENT: - Sexually dimorphic behavior: a behavior that has different forms or that occurs with different probabilities or under different circumstances in males and females- Chromosomal sex determined at time of fertilization- Gamete: mature reproductive cell; sperm or ovum (ova)- Sex chromosome: X and Y chromosome, which determine gender. - Genetic information that programs the development of a human is contained in the DNA that constitutes these chromosomes. - Y chromosome does control development of the glands that produce the male sex hormones. Sex organs: Gonads -Testes (testicles) or ovaries, first to develop-Produce ova and sperms and secrete hormones-Both sexes have a pair of undifferentiated gonads that can becomes either testes or ovaries-SRY GENE: single gene on Y chromosome producing a protein that bind to the DNA of cells in theundifferentiated fetal gonads to develop into testes -MISSING SRY: Undifferentiated gonads become ovaries -XX MALES: Sry gene become translocated from the Y to X during production of father’s sperm.-Once gonads developed: 1.) Organizational effect- during prenatal development influence developing sex organs and brain, effects permanent. 2.) Activational effect: effects occur later in life (& different in male and females) after sex organs developed. Internal genitalia -Early in embryonic development,their bisexual, all embryos contain both precursors. 1.) Mullerian System (female):precursor develops in fimbriae and fallopian tubes, uterus, and inner 2/3 of the vagina. 2.) Wolffian System: embryonic precursor of male internal sex organ into epididymis, vas deferens, and seminal vesicles. -Testes secrete 2 hormones:-Anti Mullerian (peptide) Hormone-prevents M system from developing; Has defeminizing effect reducing later development of anatomical or behavioral characteristics typical of a female.- Androgens (steroid hormones)- Male sex steroid hormone stimulates development of Wolffian system. Testosterone is the main mammalian androgen; -Masculinizing effect- 2 hormonespresent early in development thatpromotes later development of anatomical or behavioral male characteristics. 1.) Testosterone: principle androgen in males2.) Dihydrotestosterone : androgen produced from testosterone through action of an enzyme. -Androgen insensitivity syndrome: genetic mutation caused by congenital lack of functioning androgen receptors; in a person with XY sex chromes, causes development of a female with tests but no internal sex organs. (Gene for androgen receptor located on X). Primitive goands of male fetus become testes and secrete both AMH and androgens, and no masculinizing effect. AMH has defeminizingeffect, inhibits Mullerian System bc female internal sex organs don’t develop and vagina is shallow. The external genitalia arefemale, and during puberty=women’s body. Lacing uterus and ovaries, can’t have kids.-Persistent Mullerian Duct syndrome: failure to produce AMH or absence of receptors for this hormone. In males, androgens have mas. Effect but not defem. Effect, causes development of both male and female internal sex organs. -“Nature’s impulse is to create afemlae”: A chromosomal anomalyindicates that the hormones produced by female sex organs are not needed for development of Mullerian system.-Turner’s Syndrome: have only one sex (X) chromosome, bc of defective sperm. Person doesn’t have gonads at all, develop into female with normal female internal and external genitalia, proves fetuses don’t need ovaries or hormones they produce to develop as females. Without ovaries, can’t produce ova to bear children. External genitalia -Visible sex organs: 1.) Male- penis, scrotum.2.) Female-labia, clitoris, and outer vagina; these naturally develop without hormonal effects.-Gender of ext. genitalia determined by presence or absence of an androgen (ex: Dihydrotestosterone present= ext.genitalia become male)-SEX MATURATION: Stars when Neurons in the ARCUATE NUCLEUS of the HYPOTHALAMUS begin secreting Kisspeptin, which stimulates GnRH. -FSH and LH stimulate Gonads to secrete their hormones, causing genitals to mature andbody to develop secondary sex characteristics (Activational effect).Primary sex Characteristics Gonads, internal sex organs, and external genitaliaSecondary sex characteristics -enlarged breasts-widened hips-beard-deep voiceGonadotropin-Releasing Hormone (GnRH)-Onset of puberty occurs when cells in the Hypothalamus secrete GnRH, which stimulate 2 GHs by Anterior Pituitary Gland. Gonadotropic Hormone(GH): FSH , LH Hormone of the anterior pituitary gland that has a stimulating effect on cells of the gonads.1.) FSH2.) LHFollicle-Stimulating Hormone (FSH) Hormone of Ant. Pituitary Gland that causes development of an ovarian follicle and the maturation of an ovum.Luteinizing Hormone (LH) A hormone of the Ant. Pit. Gland causing ovulation and development of the ovarian follicle into a corpus luteum.Kisspeptin Peptide essential for the initiation of puberty and the maintenance of male and female reproductive ability;; controls the secretion of GnRH which directs the production and release of the GHs. Estradiol The principal estrogen of many mammals, including humans.Estrogen Class of sex hormones causing maturation of female genitalia, growth of breast tissue, and development of other physical female characteristics.CLASSIFICATION OF SEX STEROID HORMONESCLASS Principal hormone EffectsAndrogens 1.) Testosterone (testes)2.) Dihydrotestosterone (produced from testosterone by action of an enzyme)3.) Androstenedione (adrenal glands)-Development of Wolffian System.-production of sperms -growth of facial, pubic, and axillary hair-muscular development-enlargement of larynx-Inhibition of bone growth-sex drive in men (maybe women).Maturation of male external genitaliaIn women, growth of pubic and axillary hair; less important than testosterone and Dihydrotestosterone in men. Estrogen Estradiol (ovaries) -Maturation of female genitalia-growth of breast-alterations in fat deposits-growth of uterine lining-inhibition of bone growth-sex drive in women?Gestagens Progesterone: (ovaries) Maintenance of Uterine liningHypothalamicHormonesGnRH (Hypothalamus) Secretion of gonadotropinsGonadotropins FSHLH(Both anterior pituitary Gland)1.) development of Ovarian Follicle2.) Ovulation; development of Corpus LuteumOther Hormones1.)Prolactin (Ant. Pit.)2.)Oxytocin (Post. Pit.)1.) milk production; male refractory period?2.) milk ejection;