1. Aim: How does an embryo develop inside the uterus?
Do Now: Explain the difference between internal and external fertilization and development. Which one would produce more offspring? Explain.

2. How long are humans pregnant?
Females are pregnant for nine months or 40 weeks
During this time, the mother and baby undergo many changes.

3. Embryonic Development:(Review)
Fertilization
Mitosis +
Sperm
Egg
Zygote
Embryo- the stage in human development from the first division of the zygote until about eight weeks after fertilization.

4. Cleavage (Review)
The term used to describe the early cell division associated with embryonic development.
During this time period, the number of cells increase tremendously.

5. The result of cleavage is an embryo that is …..
Morula
A solid ball of cells which moves towards the uterus

6. Mitosis continues & the embryo becomes……
Blastocyst
A hollow ball of cells

7. What happens after fertilization?
The embryo travels to the uterus and implants itself in the uterus lining

8. EARLY DEVELOPMENT Cleavage occurs by mitosis
4 days the embryo = 50 cells
6-7 days = 100 cells and
Attaches to the uterine wall
(IMPLANTATION)

9. Cell division continues & the embryo starts to ….
Gastrula
Fold inwardly

10. Gastrulation Three layers
Each layer will eventually form the different organ systems
Ectoderm (skin & CNS)
Endoderm (GI Tract & lungs)
Mesoderm (muscle, bone, blood)

11. CELLULAR DIFFERENTIATION
Due to gene expression, cells undergo cellular differentiation, in which the cells become increasingly specialized in structure & function.

12. Embryo vs. Fetus Fetus Embryo (8 weeks-Birth) (Fertilization-8 weeks)
Once the embryo becomes a fetus, all the major organs have begun to form.

13. Where does the embryo develop?
In the uterus - womb
Surrounded by an amniotic sac & fluid for protection from shock

14. Why is the fetus floating in a fluid?
The fetus is surrounded by amniotic fluid and it helps absorb shock

15. What does a developing embryo need?
1. Nutrients for ATP & to build its own body parts
2. Oxygen for ATP

16. Embryonic Waste Products
1. Metabolic waste (from cells)
2. Carbon Dioxide

17. Fetal Blood Supply
The blood from the mom and the embryo NEVER mix. Materials diffuse between the mother’s blood & the baby’s blood.

18. Umbilical Cord
The umbilical cord is responsible for carrying nutrients and oxygen to the developing fetus, and waste away.

19. Placenta
The placenta is the organ that allows for the exchange of nutrients and wastes (DIFFUSION OF NUTRIENTS)

20. STRUCTURES BY 3rd WEEK Placenta
Placenta
Nervous and endocrine system (starting)
Vital organs forming
Heart is beating

21. FIRST TRIMESTER (3months)
Most major organs formed
Umbilical cord formed
Muscular system developed
Reflexes
Amnion formed

22. SECOND TRIMESTER Tissues become specialized Skeleton forms
Strong fetal heartbeat
At ~6 months the baby can live outside the mom with life support

23. 3rd Trimester Fetus doubles in size Lungs are forming
Sleeps 90-95% of the time
Dreams
Premature if born before 8 months

24. What happens at around 9 months?
The fetus has developed all its organs and is ready to live in the outside world
The uterine muscles begin to contract and the baby is forced out of the mother.
This process is called:
Labor

25. Prenatal care Good nutrition Moderate exercise No smoking
No drugs, prescription or illegal
No alcohol

26. Don’t get morning sickness: Thalidomide (1950)

27. Fetal Alcohol Syndrome (FAS)
Consuming alcohol during development can cause FAS which has disastrous affects on the CNS.
Includes:
Low birth weight
Small cranium
Organ dysfunction
Failure to thrive
Developmental delays

28. What trimester is the most dangerous?
The first trimester, because all the organs are forming at this time. Dangerous chemicals can affect cell division.