1. Embryology
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2. Essential Question:
How do we get to be?

3. I. Definition:
= The branch of biology that studies the formation and early development of living organisms 
Embryo (implantation to 8 weeks)
Fetus (after 8 weeks)
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5. Development Processes:
II. Early Embryonic
Development Processes:
A. Fertilization
B. Implantation
C. Gastrulation
D. Cell differentiation
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6. A. Fertilization:
1. =Egg and sperm come together to form a fertilized egg (called a … )
zygote
Fertilization
Human Zygote
Click for Video
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7. 2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage

8. MORULA 2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage
b. Soon a solid ball of cells is
formed, called a ....
MORULA
A scanning electron micrograph of a human embryo at the eight-cell stage (day three).
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9. Blastocyst 2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage
b. Soon a solid ball of cells is
formed, called a .... morula
c. Next, the morula will change
into a fluid filled ball of cells,
called a. . .
Blastocyst in cross-section: Cells of inner cell mass will give rise to the gastrula, outer cells will become apart of the placenta and other membranes.
Blastocyst
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10. Embryo changes days 3 to 5

11. Morula(1) to Blastocyst(2)

12. B. Implantation: The blastocyst will attach to the uterine wall.
We call this attachment IMPLANATION
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13. Implantation
Embryo

14. Click to view a video on gastrulation in humans.
C. Gastrulation:
1. The process in which the cells of the blastocyst develop into three germ layers to form a
gastrula
Click to view a video on gastrulation in humans.
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15. Gastrulation
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16. C. Gastrulation (cont.) 2. The formation of 3 germ layers a. Endoderm
Inner-most layer
(digestive tract)
b. Mesoderm
Middle layer
(internal organs)
c. Ectoderm
Outer-most layer
(skin and nervous system)
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17. Do Now……
Have your FERP, sections 3 and 4 out to be checked

18. Zygote Morula Blastocyst Gastrula
Embryo Stages
Zygote Morula Blastocyst Gastrula
Checkpoint
SUMMARY

19. D. Cell Differentiation
1. Once 3 germ cell layers formed in gastrula, then Cell differentiation (or giving cells specific jobs) begins a. 1st = neurulation i. Development of nervous system ii. Occurs soon after gastrulation is complete b. Organogenesis = organs start to form c. Morphogenesis = limbs start to assume shape

20. III. Extraembryonic Membranes
A. Membranes form to protect and nourish the developing embryo.
1 = amnion membrane forms the amniotic sac
(fluid filled cushions embryo)
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21. III. Extraembryonic Membranes (cont.)
2 = chorion forms outer most membrane.
This combined with uterine lining form the organ called the placenta
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22. The PLACENTA is a maternal-fetal organ which begins developing at implantation of the blastocyst
Exchanges
nutrients,
gases, and
waste
products
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24. Birth—3 phases Intestine Placenta Umbilical cord Wall of uterus
Vagina
Cervix
Bladder

30. IV. Stem Cells
= unspecialized cells that have the potential to differentiate