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Chapter 26c

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  1. Chapter 26c Reproduction and Development

  2. Pregnancy Prevention • Contraceptives (birth control methods) • Abstinence • Total abstinence • Abstinence during periods of female fertility • Interventional methods • Barriers • Surgery • Blocking implantation • Hormone treatments to reduce gamete production

  3. Pregnancy Prevention Table 26-5

  4. Fertilization • Sperm capacitation occurs in vagina • Sperm swim “upstream” • Sperm reach oocyte in Fallopian tube • Acrosomal reaction  digestive enzymes • Zona pellucida and cell junctions dissolve • Membranes fuse and sperm nucleu enters • Cortical reaction blocks polyspermy • Nuclear fusion creates a diploid cell • 1 sperm + 1 oocyte  1 zygote

  5. Fertilization Figure 26-16a

  6. Acrosome Reaction Allows Sperm to Reach Egg Figure 26-16b

  7. Sperm and Egg Fuse to Form a Zygote First polarbody Egg Spermnucleus Sperm nucleusmoves intocytoplasm of egg. Sperm andegg plasmamembranes fuse. Figure 26-17 (1 of 4, 2 of 4)

  8. Oocyte Completes Meiosis and Nuclei Fuse Spermnucleus Secondpolar body Egg Oocyte nucleuscompletes meioticdivision. Sperm and eggnuclei fuse toform zygote nucleus. Figure 26-17 (3 of 4, 4 of 4)

  9. Early Development • Rapid cell divisions follow fertilzation • Blastocyst • Hollow ball of ~ 100 cells • Arrives in uterus on day 4 or 5 • Implantation • Blastocyst invades the endometrium

  10. Early Development: Ovulation to Implantation 4 3 Days 2-4: Celldivision takes place. Day 4-5: Blastocystreaches uterus. 2 Day 1:Fertilization Inner cell mass Zygote Fallopiantube Egg Blastocyst 1 Ovary Ovulation 5 Days 5-9:Blastocyst implants. Uterus Figure 26-18

  11. Early Development: Ovulation Fallopiantube Egg 1 Ovary Ovulation Uterus Figure 26-18, step 1

  12. Early Development: Fertilization 2 Day 1:Fertilization Zygote Fallopiantube Egg 1 Ovary Ovulation Uterus Figure 26-18, steps 1–2

  13. Early Development: Rapid Cell Divisions 3 Days 2-4: Celldivision takes place. 2 Day 1:Fertilization Zygote Fallopiantube Egg 1 Ovary Ovulation Uterus Figure 26-18, steps 1–3

  14. Early Development: Blastocyst Reaches Uterus 4 3 Days 2-4: Celldivision takes place. Day 4-5: Blastocystreaches uterus. 2 Day 1:Fertilization Inner cell mass Zygote Fallopiantube Egg Blastocyst 1 Ovary Ovulation Uterus Figure 26-18, steps 1–4

  15. Early Development: Implantation of Blastocyst 4 3 Days 2-4: Celldivision takes place. Day 4-5: Blastocystreaches uterus. 2 Day 1:Fertilization Inner cell mass Zygote Fallopiantube Egg Blastocyst 1 Ovary Ovulation 5 Days 5-9:Blastocyst implants. Uterus Figure 26-18, steps 1–5

  16. Placenta and Continuing Development • The chorion is a tissue layer that encloses the developing embryo • The amnion is a tissue layer that secretes amniotic fluid, suspending the embryo • Chorionic villi form a close connection with blood vessels of the endometrium • The placenta continues to grow during pregnancy

  17. The Placenta Figure 26-19a

  18. The Placenta: Microscopic Anatomy Figure 26-19b

  19. The Placenta Makes Numerous Hormones • Human chorionic gonadotropin (hCG) • “Rescue” of corpus luteum • Basis of pregnancy tests • Human placental lactogen (hPL) • Breast development, metabolic effects • Estrogen and progesterone • Critical for maintaining pregnancy, and for normal development • Several additional hormones are produced

  20. Parturition: Birth Process • Prior to labor: softening of the cervix • Labor • Rhythmic uterine contractions • Positive feedback cycle of oxytocin release • Cervical dilation • Delivery of the baby • Placental release and expulsion

  21. Parturition: Birth Process Figure 26-20a

  22. Parturition: Birth Process Figure 26-20b

  23. Parturition: Birth Process Figure 26-20c

  24. Parturition: Birth Process Figure 26-20d

  25. Regulators of Parturition • Labor onset • Possible role of CRH • Stretch of cervix as a stimulus • Role of oxytocin in labor • Stretch stimulates release • Oxytocin stimulates prostaglandin release • Positive feedback (contractions stimulate more oxytocin release)

  26. Parturition Is Controlled by a Positive Feedback Loop Figure 26-21

  27. Hormones and Mammary Gland Development • Puberty • Estrogen stimulates grow of ducts and fat deposition • Pregnancy • Estrogen, growth hormone, and cortisol stimulate further gland development • Late pregnancy • Progesterone stimulates conversion of some ducts to secretory epithelium

  28. Mammary Gland Anatomy Figure 26-22a

  29. Mammary Glands - Microscopic View Figure 26-22b

  30. Lactation: Control of Milk Secretion • Before birth • Prolactin-inhibiting hormone (PIH) blocks prolactin secretion • High sex steroid levels suppress milk production • After birth • High prolactin & low estrogen  lactation • Breast milk = nutrients + immunity • Suckling • Inhibits PIH, allowing milk production • Oxytocin stimulates “let-down reflex”

  31. Hormonal Control of Milk Secretion and Release Higherbraincenters Sound ofchild’s cry Hypothalamus PIH cell Oxytocin neuron Portal system PIH Posteriorpituitary Anteriorpituitary Inhibition ofprolactin cellsis removed Prolactin Oxytocin Ascending sensory information Milksecretion Milkejected Smooth musclecontraction Mechanoreceptorsin nipple Babysuckling Figure 26-23

  32. Reproductive Maturation: Puberty • Maturation of reproductive organs, increased hormone levels, and onset of gamete production • Notable characteristics of puberty • Females: menarche, pubic hair, and breasts • Males: pubic hair, beard, and deep voice • Hormone changes at puberty • Increased secretion of GnRH • Increased LH/FSH levels stimulate gonads • Possible role of leptin

  33. Aging and Menopause • Causes • Ovaries cease responding to LH/FSH • Low levels of estrogen and progesterone • Cessation of egg development • Symptoms and therapies • Hot flashes and increased osteoporosis risk • Hormone replacement debate

  34. Aging and “Andropause” • Controversial (only affects 50% of men over 50 years) • Lower levels of testosterone impact some men’s lives • Many men remain reproductively active, despite low testosterone levels

  35. Summary • Sex and genetics • Hormonal regulation of reproduction • Tissues and hormones involved in spermatogenesis and oogenesis • Procreation and contraception • Fertilization and zygote development • Labor and delivery • Puberty, menopause, and andropause