1. Reproduction and Development
Chapter 26c
Reproduction and Development

2. Contraceptives (birth control methods)
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. Sperm capacitation occurs in vagina
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 polar body
Egg
Sperm nucleus
Sperm and egg plasma membranes fuse.
Sperm nucleus moves into cytoplasm of egg.
Figure (1 of 4, 2 of 4)

8. Oocyte Completes Meiosis and Nuclei Fuse
Sperm nucleus
Second polar body
Egg
Oocyte nucleus completes meiotic division.
Sperm and egg nuclei fuse to form zygote nucleus.
Figure (3 of 4, 4 of 4)

9. Rapid cell divisions follow fertilzation Blastocyst
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 Implantation3
Days 2-4: Cell division takes place. 4
Day 4-5: Blastocyst reaches uterus. 2
Day 1: Fertilization
Inner cell mass
Zygote
Fallopian tube
Egg
Blastocyst 1
Ovulation
Ovary
Uterus 5
Days 5-9: Blastocyst implants.
Figure 26-18

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

12. Early Development: Fertilization2
Day 1: Fertilization
Zygote
Fallopian tube
Egg 1
Ovulation
Ovary
Uterus
Figure 26-18, steps 1–2

13. Early Development: Rapid Cell Divisions3
Days 2-4: Cell division takes place. 2
Day 1: Fertilization
Zygote
Fallopian tube
Egg 1
Ovulation
Ovary
Uterus
Figure 26-18, steps 1–3

14. Early Development: Blastocyst Reaches Uterus3
Days 2-4: Cell division takes place. 4
Day 4-5: Blastocyst reaches uterus. 2
Day 1: Fertilization
Inner cell mass
Zygote
Fallopian tube
Egg
Blastocyst 1
Ovulation
Ovary
Uterus
Figure 26-18, steps 1–4

15. Early Development: Implantation of Blastocyst3
Days 2-4: Cell division takes place. 4
Day 4-5: Blastocyst reaches uterus. 2
Day 1: Fertilization
Inner cell mass
Zygote
Fallopian tube
Egg
Blastocyst 1
Ovulation
Ovary
Uterus 5
Days 5-9: Blastocyst implants.
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
Higher brain centers
Sound of child’s cry
Hypothalamus
PIH cell
Oxytocin neuron
Portal system
PIH
Anterior pituitary
Posterior pituitary
Inhibition of prolactin cells is removed
Prolactin
Ascending sensory information
Oxytocin
Milk secretion
Milk ejected
Smooth muscle contraction
Baby suckling
Mechanoreceptors in nipple
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. Symptoms and therapies
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. Hormonal regulation of reproduction
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