1. Fertilization and Development

2. Fertilization Fertilization of the Ovum occurs in the oviduct
Only one sperm allowed
Electrical block
Surface of ovum altered
Binding sites for sperm altered

4. Development Nuclei of sperm and ovum fuse to form the zygote
1st division (mitosis) Occurs in oviduct 30 hrs after fertilization

5. Development
Cell division continues as mass moves through the oviduct to the uterus
a central hollow forms and fills with fluid
Now called a blastocyst
Cells on inside develop into embryo
Outer cells develop into supportive cells
Identical Twins

6. Implantation On 6th day blastocyst breaks free of zona
Implantation blastocyst in uterine wall on day 7- 8

7. Implantation

8. Implantation Endometrium is maintained
Human corionic gonadotropic hormone (HCG) sectreted by outer cells (Chorion) of blastocyst to maintain corpus luteum
LH levels remain high
HCG used in pregnancy tests
Corpus luteum maintains levels of estrogen and progesterone to maintain endometrium

9. The Embryo
During implantation, the outer layer of cells of the blastocyst produces two membranes that surround, protect, and nourish the embryo
Chorion forms the placenta
Amnion forms amniotic sac

10. Development Considered an embryo after implantation is complete
Approx. 2 weeks from fertilization

11. Chorion

12. Amnion
Forms a fluid filled sac that insulates the embryo and fetus that protects from
Infection
Dehydration
Impact
Temperature changes

14. Umbilical cord Contains one vein and two arteries
vein carries nutrient and oxygen rich blood to the fetus.
two arteries return blood containing waste from fetal circulation back to the placenta.
It takes about 30 seconds for a blood cell to make the round trip through the cord
cord can be as long as 4 feet at birth.

15. Prenatal Development
The in’s and then outs

16. Prenatal development
Pregnancy usually last for approximately nine months
Divided into three trimesters
First Trimester
Fertilization to the end of the 3rd month
by second week – germ layers form
Ectoderm, endoderm, and mesoderm
At one month – size is only 7mm

17. Prenatal development First Trimester (Cont.)
Heart and brain have formed
heart rate can be heard at 10 weeks with a special instrument called a Doppler
Limb buds with fingers and toes present
Placenta begins developing
Considered fetus after 8th week
Movement occurs around 9th week
Sucking reflex

18. 1st Trimester

19. 12 wks
4 wks
8 wks

20. 2nd Trimester Fetus is 57 mm – 350 mm long recognizable body form
Arms, hands, fingers, legs, feet and toes are fully formed
Bone begins to replace cartilage
most of organs and tissues developed
Eyes are almost fully developed

21. 2nd Trimester

22. 16 wks
20 wks

23. 2nd Trimester At the end of 16 wks: At the end of 20 wks:
Fetus is developing reflexes such as sucking and swallowing
Sex is identifiable
Skin is bright pink, transparent and covered with soft, downy hair
At the end of 20 wks:
Mother begins to feel fetal movement
Internal organs are maturing
Eyebrows, eyelids and eyelashes appear

24. 2nd Trimester At the end of 24 weeks:
Eyelids begin to part and eyes open occasionally for short periods of time
Skin is covered with protective coating called vernix
Fetus is able to hiccup

25. 3rd Trimester Rapid growth Fetus is 350 mm – 530 mm long
Body mass increases from 0.68 kg to 3.4 kg
Organs are maturing

26. 3rd Trimester At the end of 7 months:
If born at this time, he/she will be considered a premature baby and require special care
Taste buds have developed
Fat layers are forming
Skin is still wrinkled and red

27. 3rd Trimester

28. 3rd Trimester At the end of 8 months:
Tremendous brain growth occurs at this time
Most body organs are now developed with the exception of the lungs
Movements or "kicks" are strong enough to be visible from the outside
Kidneys are mature
Skin is less wrinkled
Fingernails now extend beyond fingertips

29. 3rd Trimester At the end of 9 months: The lungs are mature
Baby is now fully developed and can survive outside the mother's body
Skin is pink and smooth
Baby settles down lower in the abdomen in preparation for birth and may seem less active

30. Parturition (Birth) Uterine contractions signal beginning of labor
Cervix thins and begins to dilate (max. 10 cm)
Labor starts when contractions are min
Amniotic membrane is forced into birth canal
Often bursts and amniotic fluid lubricates the canal (water breaking)
Usually ruptures during delivery but may occur before
Contractions start moving baby through birth canal

32. Parturition

33. Hormones involved in birth
Relaxin
Produced by placenta causes ligaments in pelvis to loosen
Oxytocin
positive feedback loop enhances strength of contractions
Prostaglandins also involved

34. Hormones involved in birth
Milk Production
Prolactin
Levels increase dramatically after birth occurs
estrogen & progesterone levels drop
Stimulates glands in the breasts to produce fluids 1.5 L/day
Oxytocin
Stimulates contractions that move milk into ducts
Also causes contractions of sm. Muscle in uterus to return to normal size