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Unit V: Development Sex Hormones

Unit V: Development Sex Hormones. Chapter 26: pp. 966-967 Chapter 16: pp. 569. Essence of Sex. Reproduction great variety of methods asexual vs. sexual Sexual reproduction each offspring has 2 parents provides genetic diversity. Functions of Reproductive System.

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Unit V: Development Sex Hormones

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  1. Unit V: DevelopmentSex Hormones Chapter 26: pp. 966-967 Chapter 16: pp. 569

  2. Essence of Sex • Reproduction • great variety of methods • asexual vs. sexual • Sexual reproduction • each offspring has 2 parents • provides genetic diversity

  3. Functions of Reproductive System • Produce and nurture sex cells • Transport gametes to site of fertilization • Secrete hormones • Secondary sex characteristics • Reproductive physiology

  4. Two Sexes • Gametes combine to form a zygote • Motility to achieve contact • has Y chromosome • contains nutrients for developing embryo • lacks Y chromosome • in mammals female also provides shelter for developing embryo (uterus and placenta)

  5. Role of Sex Chromosomes • Somatic cells contain 23 pairs of chromosomes • 22 pairs of autosomes • 1 pair of sex chromosomes (XY males: XX females) • 50% sperm carry Y; 50% X • all eggs carry the X chromosome • Sex of child determined by type of sperm that fertilizes mother’s egg • Meiosis – series of two cell divisions that cut chromosome number in half • diploid  haploid  fertilization  diploid

  6. Hormones and Sex Differentiation • Gonads begin to develop at 6 weeks • Gonadal ridges • mesonephric ducts vas deferens • paramesonephric ducts (müllerian ducts)  oviduct • SRY gene • in males, codes for a protein (TDF) that causes development of testes  • secrete testosterone • secrete müllerian-inhibiting factor degenerates paramesonephric ducts • Female development occurs in absence of androgens

  7. Fig. 27.3-2 Mesonephros Mesonephric duct Paramesonephric (müllerian) duct Gonadal ridge Kidney Cloaca 5- to 6-week embryo; sexually indifferent stage Male Female Testes Ovaries Efferent ductules Paramesonephric duct forming the uterine tube Epididymis Paramesonephric duct (degenerating) Mesonephric duct (degenerating) Mesonephric duct forming the ductus deferens Fused paramesonephric ducts forming the uterus Urinary bladder Urinary bladder (moved aside) Seminal vesicle Urogenital sinus forming the urethra Urogenital sinus forming the urethra and lower vagina 7 to 8 weeks 8 to 9 weeks

  8. Adrenal Gland • Adrenal Cortex: • sex steroids • Skeletal growth and sustain adult bone mass • Development of pubic, axillary hair, apocrine glands • Sustain sex drive • androgen – male sex hormones • DHEA  testosterone • Meets 50% requirement in women • estrogen (estradiol) • Important after menopause

  9. Adrenogenital Syndrome (AGS) • Hypersecretion of androgens • In children: • Causes enlargement • Premature onset of puberty • In women and fetus: • Masculinizing effects

  10. Female Sex Hormones • Estrogens • estradiol, estrone, and estriol • Progesterone • changes in uterus during menstrual cycle (pregnancy) • affects mammary glands • regulates secretion of LH and FSH • Androgens • development of female skeleton • Inhibin

  11. Female Sex Hormones Responses to Estrogens in Females Integumentary System Produce vellus hairs, terminal hair in axillae and genital area Initial development of the mammary glands Skeletal System More rapid epiphyseal closure Thus skeletal growth is brief Muscular System Growth of skeletal muscle fibersThus increasing strength and endurance Nervous System At puberty, activates CNS centers involved in female sexual drive and sexual behaviors Cardiovascular System Menstrual cycle ↑ risk of iron-deficiency anemia Estrogens ↓ plasma cholesterol levels and slow the formation of plaque within arteries. Respiratory System Less growth of the larynx and vocal cords Thus females have higher-pitched voices Reproductive System Thicken of the myometrium↑ blood flow to the endometriumDevelopment of accessory reproductive structures

  12. HYPOTHALAMUS Release of Gonadotropin-Releasing Hormone (GnRH) The Gonads:Ovaries Stimulates the production andsecretion of FSH and the production—but not the secretion—of LH. GnRH ANTERIOR LOBE OFPITUITARY GLAND Production of LH FSH Secretion of LH Negative feedback Afterday 10 Beforeday 10 • Ovulation • Follicle development OVARY • Corpus luteum • Inhibin • Estradiol Progesterone Secondary Sexcharacteristics Reproductive System Stimulation ofendometrial growth and secretion KEY Stimulation Inhibition

  13. Responses to Testosterone in Males Male Sex Hormones Integumentary System Terminal hairs on the face and chest, axillae and genital area Adipose tissues respond differently totestosterone than to estrogens Skeletal System Accelerates bone deposition and skeletal growth Promotes closure of the epiphyseal cartilages Muscular System Stimulates the growth of skeletal muscle fibers Nervous System A t puberty, activates the CNS centers concerned with male sexual drive and sexual behaviors. Cardiovascular System Stimulates erythropoiesis, thereby increasing bloodvolume and the hematocrit. Respiratory System Stimulates disproportionate growth of the larynxThickening and lengthening of the vocal cords Gradual deepening of the voice Reproductive System Development of the accessory reproductive glandsHelps promote spermatogenesis.

  14. The Gonads:Testes Negative feedback GnRH Peripheral Effects HYPOTHALAMUS Released relatively steady. Nervous System Skeletal System Secondary sex characteristics TESTES Interstitial Cell LH Reproductivesystem Testosterone ANTERIOR LOBE OF THE PITUITARY GLAND Spermatogenesis and spermiogenesis. Sustenacular Cells FSH Androgen-binding protein (ABP)binds androgens ofseminiferous tubules Maturation ofspermatids. Targets seminiferous tubules. Respond to factors released by developing spermatozoa Inhibin Negative feedback KEY Stimulation Inhibition

  15. The Gonads:Testes

  16. Androgen-Insensitivity Syndrome(Testicular Feminization) • Genetically male • Target cells lack receptors for testosterone • Female anatomy • no menstruation or uterus • presence of testes in abdomen

  17. Overview of Reproductive System • Primary sex organs • produce gametes • Secondary sex organs • male - ducts, glands, penis • female - uterine tubes, uterus and vagina • Secondary sex characteristics • develop at puberty to attract a mate • pubic, axillary and facial hair, scent glands, body morphology and low-pitched voice in males

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