1. Pregnancy & Human Development
Chapter 29

2. Fertilization: It’s all in the timing!
Oocyte is only viable for ~ 24 hours.
Sperm is viable for 12 – 24 hours (some “super sperm” may be viable for up to 72 so be careful!)
Therefore, usually, coitus must occur within a 24 hour window on either side of ovulation.

3. Barriers to fertilization
Low vaginal pH
Getting lost (50/50 chance of getting the right uterine tube)
Numerous defective sperm
Uterine contractions
Phagocytes
By the time they get to the oocyte, there are only a few dozen to a couple hundred

4. Capacitation
Must occur before spermatozoa can fertilize secondary oocyte:
contact with secretions of seminal vesicles
exposure to conditions in female reproductive tract

5. Penetration
Secondaryoocyte
Head of sperm
1650X

6. Fertilization
Figure 29–1

7. Fertilization
Figure 29–1b (1 of 2)

8. Fertilization
Figure 29–1b (2 of 2)

9. Fusion Of the pronuclei

10. Cleavage and Blastocyst Formation
Figure 29–2

11. What’s this thing called, Love?
Zygote – a the single cell after fusion of the pronuclei of the oocyte & the sperm.
Conceptus – covers the period of develop following first cleavage and differentiation of cells into an embryo.
Morula – the conceptus as a solid ball of 16 cells (about day 3).
Blastocyst – a hollow ball of cells, from day 4. “Hatching” occurs at this stage, when the blastocyst emerges from the zona pellucida.

12. Development from zygote to implantation.

13. Then what ? The blastocyst differentiates into:
the trophoblast, the outer ball of cells that eventually becomes the placenta and “extraembryonic” membranes.
the inner cell mass (ICM) becomes the embryo.
The above occurs over the course of the second week following conception.
Implantation – occurs on about day 6 or so, as the blastocyst burrows into the endometrium.

14. Stages in Implantation
Figure 29–3

15. Implantation
Day 6

16. Implantation – Day 8

17. Implantation Days 9 - 13 and early placentation

18. Ectopic Pregnancy Implantation occurs outside of uterus
Do not produce viable embryo
Can be life threatening

19. The Inner Cell Mass and Gastrulation
Figure 29–4

20. The Primary Germ Layers
ECTODERM
MESODERM
ENDODERM
All nervous tissue
Muscle
G.I. epithelium
Epidermis & Derivatives
Connective tissue
Digestive glands
Cornea & lens
Lymphoid tissue
Reproductive ducts & gland epithelium
Oral, nasal & anal epithelium
Endothelium of blood vessels
Thyroid, thymus & parathyroid
Tooth enamel
Serosae
Urethra & bladder epithelium
Pineal, pituitary & adrenal medulla
Eye’s fibrous & vascular tunics
Respiratory tract epithelium
Melanocytes
Synovia
Flat bones of cranium
Urogenital organs

21. The Fates of the Germ Layers
Table 29–1

22. Extraembryonic Membranes and Placenta Formation
Figure 29–5 (1 of 3)

23. Figure 29–5 (2 of 3)

24. Placenta Formation
Figure 29–5 (3 of 3)

25. View of Placental Structure
Figure 29–6a

26. Placental Structure
Figure 29–6b

27. Decidua: Decidua Capsularis Decidua Basalis Decidua Parietalis
Thin portion of endometrium
No longer participates in nutrient exchange and chorionic villi in region disappear
Decidua Basalis
Disc-shaped area in deepest portion of endometrium
Where placental functions concentrated
Decidua Parietalis
Rest of the uterine endometrium
No contact with chorion

28. Hormones of Placenta
Synthesized by syncytial trophoblast, released into maternal bloodstream:
human chorionic gonadotropin
human placental lactogen
placental prolactin
relaxin
progesterone
estrogens

29. Human Placental Lactogen (hPL)
Helps prepare mammary glands for milk production
Stimulatory effect on other tissues comparable to growth hormone (GH)
Placental Prolactin
Helps convert mammary glands to active status

30. Relaxin Is a peptide hormone
Is secreted by placenta and corpus luteum during pregnancy
Increases flexibility of pubic symphysis, permitting pelvis to expand during deliveryCauses dilation of cervix
Suppresses release of oxytocin by hypothalamus and delays labor contractions

31. An Overview of Prenatal Development
Table 29–2 (1 of 4)

32. An Overview of Prenatal Development
Table 29–2 (2 of 4)

33. An Overview of Prenatal Development
Table 29–2 (3 of 4)

34. An Overview of Prenatal Development
Table 29–2 (4 of 4)

35. Embryogenesis Body of embryo begins to separate from embryonic disc
Body of embryo and internal organs start to form
Folding, differential growth of embryonic disc produce bulge that projects into amniotic cavity:
projections are head fold and tail fold

36. The First Trimester
Figure 29–7a, b

37. The First Trimester
Figure 29–7c, d

38. Organogenesis
Process of organ formation

39. The Second and Third Trimesters
Figure 29–8

40. Second Trimester
Fetus grows faster than surrounding placenta

41. Third Trimester Most of the organ systems become ready
Growth rate starts to slow
Largest weight gain
Fetus and enlarged uterus displace many of mother’s abdominal organs

42. Growth of the Uterus and Fetus
Figure 29–9a, b

43. Growth of the Uterus and Fetus

44. Progesterone Released by placenta
Has inhibitory effect on uterine smooth muscle
Prevents extensive, powerful contractions

45. Opposition to Progesterone
3 major factors:
rising estrogen levels
rising oxytocin levels
prostaglandin production

46. Initiation of Labor and Delivery
Figure 29–10

47. False Labor True Labor Occasional spasms in uterine musculature
Contractions not regular or persistent
True Labor
Results from biochemical and mechanical factors
Continues due to positive feedback

48. Hormone levels throughout pregnancy

49. Placental hormones

50. Contractions Begin near top of uterus, sweep in wave toward cervix
Strong, occur at regular intervals, increase in force and frequency
Change position of fetus, move it toward cervical canal

51. Stages of Labor
Dilation stage
Expulsion stage
Placental stage

52. Dilation Stage Begins with onset of true labor Cervix dilates
Fetus begins to shift toward cervical canal
Highly variable in length:
typically lasts over 8 hours

53. Dilation Stage Frequency of contractions steadily increase
Amniochorionic membrane ruptures (water breaks)

54. The Stages of Labor
Figure 29–11 (1 of 2)

55. Expulsion Stage Begins as cervix completes dilation
Contractions reach maximum intensity
Continues until fetus has emerged from vagina:
typically less than 2 hours

56. The Stages of Labor
Figure 29–11 (2 of 2)

57. Delivery Episiotomy Arrival of newborn infant into outside world
Incision through perineal musculature
Needed if vaginal canal is too small to
pass fetus
Repaired with sutures after delivery

58. Fetal circulation

59. The Beginning
Next - Inheritance

60. Cesarean Section
Removal of infant by incision made through abdominal wall
Opens uterus just enough to pass infant’s head
Needed if complications arise during dilation or expulsion stages

61. Placental Stage
Muscle tension builds in walls of partially empty uterus
Tears connections between endometrium and placenta
Ends within hour of delivery with ejection of placenta, or afterbirth
Accompanied by a loss of blood

62. Actual placenta

63. Premature Labor
Occurs when true labor begins before fetus has completed normal development
Newborn’s chances of surviving are directly related to body weight at delivery

64. Immature Delivery Refers to fetuses born at 25–27 weeks of gestation
Most die despite intensive neonatal care
Survivors have high risk of developmental abnormalities

65. Premature Delivery Refers to birth at 28–36 weeks
Newborns have a good chance of surviving and developing normally

66. Forceps Delivery
Needed when fetus faces mother’s pubis instead of sacrum
Risks to infant and mother are reduced using forceps:
forceps resemble large, curved salad tongs
used to grasp head of fetus

67. Breech Birth
Legs or buttocks of fetus enter vaginal canal first instead of head
Umbilical cord can become constricted, cutting off placental blood flow
Cervix may not dilate enough to pass head
Prolongs delivery
Subjects fetus to severe distress and potential injury

68. 5 Life Stages Neonatal period - Extends from birth to 1 month
Infancy - 1 month to 2 years of age
Childhood - 2 years until adolescence
Adolescence - Period of sexual and physical maturation
Maturity

69. Colostrum Secretion from mammary glands
Ingested by infant during first 2–3 days
Contains more proteins and less fat than breast milk:
many proteins are antibodies that help ward off infections until immune system is functional

70. Colostrum Mucins present inhibit replication of rotaviruses
As production drops, mammary glands convert to milk production

71. Breast Milk Consists of: water proteins amino acids lipids sugars
salts
large quantities of lysozymes—enzymes with antibiotic properties

72. Milk Let-Down Reflex
Mammary gland secretion triggered when infant sucks on nipple
Continues to function until weaning, typically 1–2 years

73. The Milk Let-Down Reflex
Figure 29–12

74. Benefits of Breast-feeding
Acquired immune defenses
Neutrophils, macrophages, T and B cells
Immunoglobulin A
Reduced incidence of later diseases in child
Lymphoma, heart disease, gastrointestinal disorders, diabetes mellitus & meningitis
In mother
Reduced incidence of osteoporosis and breast cancer
Stronger bonding, less post-partum depression,
More rapid weight loss, uterine recovery

75. Growth and Changes in Body Form and Proportion
Figure 29–13

76. From embryo to fetus