Download
chapter 26a n.
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 26a PowerPoint Presentation
Download Presentation
Chapter 26a

Chapter 26a

206 Vues Download Presentation
Télécharger la présentation

Chapter 26a

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Chapter 26a Reproduction and Development

  2. About this Chapter • Sex determination and differentiation • Gametogenesis and patterns of reproduction • Male reproductive development and physiology • Female reproductive development and physiology • Pregnancy and the birth process • The reproductive system during growth and aging

  3. Sex Determination • Sexual dimorphism • Females and males are physically distinct • Gonads produce gametes and sex hormones • Male gonads = testes  sperm • Female gonads = ovaries  eggs • Sex hormones direct development of genitalia • Internal genitalia • External genitalia

  4. Sex Determination Is Directed By Our Genome • Humans have 23 pairs of chromosomes • 22 pairs of autosomes • X and Y = 1 pair of sex chromosomes Nondisjunction • XXX superfemale • XXY Klinefelters • X0 Turners • XYY supermale Figure 26-1

  5. X and Y Chromosomes Determine Sex Figure 26-2

  6. Sexual Differentiation • Bipotential tissues have not yet differentiated • SRY protein directs development as a male • Gonadal medulla develops into testis • Testicular hormones direct further development • Absence of SRY protein leads to female development • Gonadal cortex develops into ovarian tissue • Mullerian ducts develop into female organs • Wolffian ducts degenerate

  7. Sexual Differentiation Table 26-1

  8. Development of Internal Reproductive Organs Müllerian duct Wolffian duct Bipotential gonad Kidney Cloacal opening FEMALE MALE Bipotential stage: 6 week fetusThe internal reproductive organshave the potential to develop intomale or female structures 1 1 SRY protein in a maleembryo directs themedulla of thebipotential gonadto develop into testis. Gonadal cortexbecomes ovary in theabsence of SRY protein. Testis Absence of testosteronecauses Wolffian ductto degenerate. 2 2 Anti-Müllerianhormone from testiscauses the Müllerianducts to disappear. Wolffianduct Müllerian duct Uterus 10 WEEKS Ovary 3 Testosterone fromtestis converts Wolffianduct into seminalvesicle, vas deferens,and epididymis. DHTcontrols prostatedevelopment. Prostate Absence of anti-Müllerian hormoneallows theMüllerian ductto become thefallopian tube,uterus, and upperpart of the vagina. 3 Seminal vesicle Fallopian tube(from Müllerianduct) Vas deferens Uterus Testis AT BIRTH Epididymis Vagina (a) DEVELOPMENT OF INTERNAL ORGANS Figure 26-3a

  9. Development of External Genitalia Genital tubercle Urethral groove homologous Labioscrotal swelling Urethral fold Anus FEMALE MALE Bipotential stage(6 week fetus) Clitoris Penis Urethral fold Urethral fold Labioscrotalswelling Labioscrotalswelling Anus Anus 1 DHT causesdevelopmentof male externalgenitalia. 10 WEEKS 1 1 In the absenceof androgens,the external genitaliaare feminized. Glans penis Labiamajora Clitoris Shaft of penis Urethral opening Labiaminora Vaginal opening Scrotum 2 The testes descendfrom the abdominalcavity into thescrotum. Anus Anus AT BIRTH (b) DEVELOPMENT OF EXTERNAL GENITALIA Figure 26-3b

  10. Control of Male Development • SRY gene directs male development Figure 26-4

  11. Control of Female Development • The SRY gene and protein are absent • Gonadal cortex develops into ovarian tissue • Mullerian ducts develop into female organs • Vagina • Uterus • Fallopian tubes • Wolffian ducts degenerate

  12. Gametogenesis Differs in Males and Females FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation 46 chromosomesper cell (only twoshown here) Embryo Embryo 46(diploid) Oögonia Spermatogonia MEIOSIS 2 DNA replicatesbut no cell division. Primaryoocyte Primaryspermatocyte Sisterchromatids Sisterchromatids 46 chromosomes,duplicated 3 First meioticdivision First polarbody Secondaryoocyte(egg) Reproductive adult Secondaryspermatocytes Primary gamete dividesinto two secondary gametes. 23 chromosomes,duplicated (may notoccur) Reproductive adult 4 Second meioticdivision Spermatids Disintegrates Egg releasedfrom ovary atovulation. Secondary gamete divides. develop into 23 chromosomes(haploid) Sperm FERTILIZATION 6 One primary oocyteyields 1 egg. One primary spermatocyteyields 4 sperm. 5 Secondpolar bodydisintegrates. Unfertilized eggpasses out of body. Zygote Figure 26-5

  13. Mitosis: Germ Cell Proliferation FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation 46 chromosomesper cell (only twoshown here) Embryo Embryo 46(diploid) Oögonia Spermatogonia Reproductive adult Reproductive adult Figure 26-5, step 1

  14. Meiosis: DNA Replicates FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation 46 chromosomesper cell (only twoshown here) Embryo Embryo 46(diploid) Oögonia Spermatogonia MEIOSIS 2 DNA replicatesbut no cell division. Primaryoocyte Primaryspermatocyte Sisterchromatids Sisterchromatids 46 chromosomes,duplicated Polar bodies Reproductive adult Reproductive adult Figure 26-5, steps 1–2

  15. First Meiotic Division FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation 46 chromosomesper cell (only twoshown here) Embryo Embryo 46(diploid) Oögonia Spermatogonia MEIOSIS 2 DNA replicatesbut no cell division. Primaryoocyte Primaryspermatocyte Sisterchromatids Sisterchromatids 46 chromosomes,duplicated Polar bodies 3 First meioticdivision First polarbody Secondaryoocyte(egg) Reproductive adult Secondaryspermatocytes Primary gamete dividesinto two secondary gametes. 23 chromosomes,duplicated Reproductive adult Figure 26-5, steps 1–3

  16. Second Meiotic Division FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation 46 chromosomesper cell (only twoshown here) Embryo Embryo 46(diploid) Oögonia Spermatogonia MEIOSIS 2 DNA replicatesbut no cell division. Primaryoocyte Primaryspermatocyte Sisterchromatids Sisterchromatids 46 chromosomes,duplicated Polar bodies 3 First meioticdivision First polarbody Secondaryoocyte(egg) Reproductive adult Secondaryspermatocytes Primary gamete dividesinto two secondary gametes. 23 chromosomes,duplicated (may notoccur) Reproductive adult 4 Second meioticdivision Spermatids Disintegrates Egg releasedfrom ovary atovulation. Secondary gamete divides. develop into 23 chromosomes(haploid) Sperm One primary spermatocyteyields 4 sperm. Figure 26-5, steps 1–4

  17. Ovulation Without Fertilization FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation Embryo 46 chromosomesper cell (only twoshown here) Embryo 46(diploid) Oögonia Spermatogonia MEIOSIS 2 DNA replicatesbut no cell division. Primaryoocyte Primaryspermatocyte Sisterchromatids Sisterchromatids 46 chromosomes,duplicated Polar bodies 3 First meioticdivision First polarbody Secondaryoocyte(egg) Reproductive adult Secondaryspermatocytes Primary gamete dividesinto two secondary gametes. 23 chromosomes,duplicated (may notoccur) Reproductive adult 4 Second meioticdivision Spermatids Disintegrates Egg releasedfrom ovary atovulation. Secondary gamete divides. develop into 23 chromosomes(haploid) Sperm One primary oocyteyields 1 egg. One primary spermatocyteyields 4 sperm. 5 Unfertilized eggpasses out of body. Figure 26-5, steps 1–5

  18. Ovulation with Fertilization Is Followed by Final Step of Meiosis FEMALE STAGE OF CELL DIVISION MALE Spermatogonium 1 MITOSIS Oögonium Germ cell proliferation 46 chromosomesper cell (only twoshown here) Embryo Embryo 46(diploid) Oögonia Spermatogonia MEIOSIS 2 DNA replicatesbut no cell division. Primaryoocyte Primaryspermatocyte Sisterchromatids Sisterchromatids 46 chromosomes,duplicated Polar bodies 3 First meioticdivision First polarbody Secondaryoocyte(egg) Reproductive adult Secondaryspermatocytes Primary gamete dividesinto two secondary gametes. 23 chromosomes,duplicated (may notoccur) Reproductive adult 4 Second meioticdivision Spermatids Disintegrates Egg releasedfrom ovary atovulation. Secondary gamete divides. develop into 23 chromosomes(haploid) Sperm FERTILIZATION 6 One primary oocyteyields 1 egg. One primary spermatocyteyields 4 sperm. 5 Secondpolar bodydisintegrates. Unfertilized eggpasses out of body. Zygote Figure 26-5, steps 1–6

  19. Steroid Synthesis Pathways • Steroid hormones are similar to each other • Production of sex steroids differs between men and women • Ovary • Estrogen and progesterone • Testis • Testosterone and dihydrotestosterone (DHT) • Adrenal gland secretes small amounts of sex steroids

  20. Synthesis Pathways for Steroid Hormones Cholesterol Progesterone Dihydro-testosterone(DHT) * Testosterone aromatase Corticosterone Cortisol Estradiol KEY * 5-reductase Aldosterone Intermediate steps Figure 26-6

  21. Hormonal Regulation of Reproduction • Anterior pituitary • Luteinizing hormone (LH) • Follicle stimulating hormone (FSH) • Gonads produce steroid and peptide hormones • Gonads are the main source of sex steroid

  22. General Pattern of Hormonal Control of Reproduction Internal andenvironmentalstimuli CNS GnRH Hypothalamus Short-loop negative feedback KEY Stimulus Anteriorpituitary Integrating center Efferent pathway Effector Long-loop feedbackmay be negativeor positive Tissue response LH FSH Gonads(ovaries or testes) Females only Endocrinecells Gameteproduction Steroid andpeptide hormones Figure 26-7

  23. Consequences of Feedback Table 26-2