Prenatal Development
Week 4
Prenatal Development
• 3 Trimester’s: 1st, 2nd & 3rd
• 3 Periods (stages): Germinal, embryonic & fetal
• 38 weeks
Milestones of Prenatal Dev.
Table 2.2 (p. 61)
• 1st Trimester – weeks 1 to 12 (germinal/zygote, embryonic, &
early part of fetal period)
• 2nd Trimester - weeks 13 to 24 (fetal period)
• 3rd Trimester - weeks 25 to 38 (fetal period)
Part 2
 Gestation- lasts about 38 wks
Germinal Stage (zygote): First 14 days of the pregnancy
• Zygote implants into the uterus lining…
Stages of Prenatal Development
1) The endoderm layerwill develop into internal organs & glands
Stage of the Embryo
2) The ectoderm layer- become the parts of the body that
maintain contact w/ the outside world: the nervous system;
• 3) The mesoderm layer- muscles, cartilage, bone, sex organs
(reproductive sys), & the heart (circulatory sys).
 Amniotic sac- watertight membrane filled w/ fluid…
 The placenta-organ through which the organism/mother
exchange materials.
The Prenatal Environment
• The umbilical cord-links the organism to the placenta; it
serves as a filter…
Stage of the fetus
• The main changes for the fetus are to develop further the
already formed organ structures & increase in size & weight
• From 3- 4 mos.,
• By 4th mos. mother produces colostrum …
• By 4th mos. lanugo and covers the body and vernix is secreted.
Conception to Birth
• http://www.youtube.com/watch?v=fKyljukBE70
• Start at 2 min; STOP at 5:52
Small Group Discussion
• How has your culture influenced the way a woman/man,
experiences pregnancy (i.e. – beliefs, practices, traditions,
etc.)?
• What about the father/partner?
The 9th month- Pregnancy around the World
• http://www.pri.org/stories/2014-02-23/video-shes-seven-monthspregnant-and-still-working-fields
• Stop at 5 min 10 seconds
Teratogens
Non-genetic agents that can cause malformation in the embryo / fetus.
1930’s:
Mid 1940’s:
1960’s: