1. Fetal Development

2. Differentiation is the process in which each of the three layers of the gastrula develop into different specialized cells in the body The pregnancy is broken up into 3 sections called trimesters depending on the period of time during which the tissues and organs form, in other words when differentiation occurs – First, Second and Third Trimesters = approx 3months each

3. The First Trimester7wks

4. The First Trimester Embryonic Phase First 4 weeks Organs begin to develop Formation of the placenta (nutrition and waste removal) Formation of the amnion (amniotic fluid for protection)

5. The First Trimester Embryonic Phase 4 wks

6. The Fetus At around 8-9 weeks the first bone cell forms Until now the developing human has been called an embyro After the first bone cells form, it is called a fetus until birth Bone formation is called ossification

7. The First Trimester Fetal Phase 8 weeks Fetus is approximately the size of a bean (3cm) Bone formation Tail disappears and turns to tailbone (coccyx) Appendages, hands and joints form Beginning formation of tubes for respiratory system Nervous system starts to form

8. The First Trimester Fetal Phase 8 wks

9. The First Trimester 12 weeks Eyes and ears form Kidneys have formed and become functional The nervous system continues to develop and more connections are formed The fetus can actually suck its thumb

10. The First Trimester 12 weeks

11. The First Trimester By the end of the first trimester, 12 weeks... the fetus measures 5-10cm the fetus has a noticable head and limbs all the major organ systems have started to form: -including liver, stomach, brain, kidneys, heart

12. The Second Trimester 13 - 24 weeks 16 weeks Fetus weighs about 100g Circulatory and urinary systems become functional Heart beat is strong and loud enough to be heard with stethoscope Eyes begin to move Toenails grow Skeleton begins to form Sex is recognizable externally

13. The Second Trimester 16 wks

14. The Second Trimester18wks

15. The Second Trimester 20 weeks Skin is coated with waxy substance (vernix) to protect it from amniotic fluid Fetus is able to swallow Digestive system begins to produce meconium

16. The Second Trimester 20 wks

17. The Second Trimester 24 weeks Fetus weighs 2kg and measures 30cm Fetus begins to accumulate fat Skin is thin and translucent Taste buds form Lungs continue to develop Pulmonary surfactant is a fluid produced so that lungs can inflate

18. The Second Trimester 24wks

19. The Second Trimester By the end of the second trimester, 24 weeks... most of the organs have formed but are still developing the legs have been developing and movement can be felt the brain has been growing rapidly the nervous system begins to function at this stage the fetus is viable, but its chances of survival if born now are not good

20. The Third Trimester 25 – 40wks The third trimester is for fetal growth Nails and hair continue to grow Eyes are open (in 8 th month) Accumulation of large amounts of fat Lots of movement happening – kicking Brain continues to grow and develop Fetus requires significant amount of calories so nutrition for the mother and fetus is crucial Immune system develops

21. The Third Trimester26wks

22. The Third Trimester 35wks

23. The Third Trimester By the end of the third trimester, 38-40wks... the bones of the skull have not completely fused -the fontanel is present for birth when born the fetus is about 50cm and approximately 3kg

24. The Placenta The fetus is reliant on the mother for oxygen and nutrients. The placenta allows the exchange of oxygen and nourishment from the mother to the fetus.

25. The Placenta

27. The Third Trimester39wks One week before birth

28. Birth

29. The Umbilical Cord