1. Chapter 4: Prenatal Development
and Birth
Importance:
1. Hereditary endowment is fixed
2. Favorable conditions in the mother’s
body
3. Proportionally greater growth and
development takes place
4. Influence of significant people

2. Major Phases of Prenatal Development
 Scientific term used to describe baby-to-
be
 Major developments in each period

3. I. Germinal Period
Period of the Zygote
8-14 days or Weeks 1-2
Conception until implantation

4. Germinal Period

5. Germinal Period

6. Germinal Phase

7. Germinal Phase

8. Germinal Phase

9. Germinal Period

10. Germinal Period

11. Germinal Period

12. Germinal Period

13. Germinal Period

14. Implantation

15. Implantation

16. II. Period of the Embryo
 When zygote is completely embedded in
the uterine wall
 Body structures and internal organs
develop
 3 layers begin to form in the embryo:
1. Ectoderm: hair, skin, nervous system
2. Mesoderm: muscles, bones, circulatory
system
3. Endoderm: digestive system and lungs

17. Period of the Embryo
 Embryo rests in a sac called amnion
amniotic fluid shock-absorbing
protection; constant
temperature
 Chorion: 2nd membrane after about a
month of development; helps form the
placenta
 Weeks 3-8

18. Period of the Embryo
 3-week old: salamander
 8-week old: most of the organs found in a
mature human are in place; visible eyes,
jaw, arms and legs
 About 1 inch long and weighs only a
fraction of an ounce

19. Period of the Embryo

20. Period of the Embryo

21. Period of the Embryo

22. Period of the Embryo

23. Period of the Embryo

24. III. Period of the Fetus
 Weeks 9-38
 Much larger and bodily systems begin to
work (respiration, digestion, vision)
 By 22-28 weeks, most systems function
well enough that a fetus has a chance to
survive
age of viability

25. Period of the Fetus
 Distinct baby-like look
 May still have trouble breathing and
cannot regulate body temperature yet
 Fetus starts to behave as movements
become obvious
 Begins to hear sounds, taste different
flavors

26. Period of the Fetus:
3rd Month

27. Period of the Fetus:
4th Month

28. Period of the Fetus:
5th Month

29. Period of the Fetus:
6th Month

30. Period of the Fetus:
7th Month

31. Period of the Fetus:
8th Month

32. Period of the Fetus:
9th Month

33. Changes in a pregnant woman’s body