1. Embryology
Image from:

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)
Gestation: carrying of an embryo/fetus inside a female
Lasts 9 months
Image from:

5. Development Processes:
II. Early Embryonic
Development Processes:
A. Fertilization
B. Implantation
C. Gastrulation
D. Cell differentiation
Images from: ;

6. A. Fertilization:
1. =Egg and sperm come together to form a fertilized egg (called a … )
zygote
Fertilization
Human Zygote
Click for Video
Gestation officially begins
Images from:

7. Before Fertilization…
Spermatogenesis: Sperm produced through meiotic divisions (meiosis) in testes
Oogenesis: Formation of the ovum (female’s egg cell) in the ovaries through meiotic divisions

8. 2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage

9. 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).
Image from:

10. 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
Image from:

11. Embryo changes days 3 to 5

12. Morula(1) to Blastocyst(2)

13. FERTILIZATION 1. Zygote 2. Morula 3. Blastula
Egg and sperm come together to form a fertilized egg
First few mitotic cell divisions are called cleavage
2. Morula
solid ball of cells is formed (the eight-cell stage - day 3)
3. Blastula
fluid filled ball of cells called a blastocyst (day 5)

14. B. Implantation: The blastocyst attaches to the uterine wall.
Attaches through placenta
Placenta begins to release hormone HCG (human Chorionic Gonadotropin)
Image from:

15. Implantation
Embryo

16. 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.
Image/video from:

17. Gastrulation
Images from:

18. 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)
Images from:

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

20. D. Cell Differentiation
1. Cells specialize in order to perform specific function a. Neurulation: Development of nervous system ii. Occurs soon after gastrulation is complete b. Organogenesis = organs start to form c. Morphogenesis = limbs start to assume shape

21. III. Extraembryonic Membranes
A. Membranes form to protect and nourish the developing embryo.
1 = amnion membrane forms the amniotic sac
(fluid filled cushion that contains and protects the fetus)
Image from:

22. III. Extraembryonic Membranes (cont.)
2 = chorion forms outer most membrane.
This, combined with the uterine lining, form the organ called the placenta
Image from:

23. The PLACENTA is a maternal-fetal organ which begins developing at implantation of the blastocyst
Exchanges
nutrients,
gases, and
waste
products
Image from:

25. Birth—3 phases Intestine Placenta Umbilical cord Wall of uterus
Vagina
Cervix
Bladder

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

32. *Limited in what they can become
4 Types of Stems
MULTIPOTENT
PLURIPOTENT
ADULT
TOTIPOTENT
Potential to give rise to any & all tissue types of cells
*Can give rise to an entire organism
*Same as totipotent but can’t create an entire organism
*Limited in what they can become
*Blood, skin, and nerve cells
*Undiff. cells found among diff. cells
*Replenish dying cells

33. Stem Cell Types 1. Totipotent Stem Cells
These are the most versatile of the stem cell types. When a sperm cell and an egg cell unite, they form a one-celled fertilized egg. This cell is totipotent, meaning it has the potential to give rise to any and all human cells, such as brain, liver, blood or heart cells. It can even give rise to an entire functional organism. The first few cell divisions in embryonic development produce more totipotent cells. After four days of embryonic cell division, the cells begin to specialize into pluripotent stem cells.
2. Pluripotent Stem Cells
These cells are like totipotent stem cells in that they can give rise to all tissue types. Unlike totipotent stem cells, however, they cannot give rise to an entire organism. On the fourth day of development, the embryo forms into two layers, an an outer layer which will become the placenta, and an inner mass which will form the tissues of the developing human body. These inner cells, though they can form nearly any human tissue, cannot do so without the outer layer; so are not totipotent, but pluripotent. As these pluripotent stem cells continue to divide, they begin to specialize further.
Source: Brown University, Division of Biology and Medicine—Retrieved from:

34. Stem Cell Types cont. 3. Multipotent Stem Cells
These are less plastic and more differentiated stem cells. They give rise to a limited range of cells within a tissue type. The offspring of the pluripotent cells become the progenitors of such cell lines as blood cells, skin cells and nerve cells. At this stage, they are multipotent. They can become one of several types of cells within a given organ. For example, multipotent blood stem cells can develop into red blood cells, white blood cells or platelets
4. Adult Stem Cells
An adult stem cell is a multipotent stem cell in adult humans that is used to replace cells that have died or lost function. It is an undifferentiated cell present in differentiated tissue. It renews itself and can specialize to yield all cell types present in the tissue from which it originated. So far, adult stem cells have been identified for many different tissue types such as hematopoetic (blood), neural, endothelial, muscle, mesenchymal, gastrointestinal, and epidermal cells.
Source: Brown University, Division of Biology and Medicine—Retrieved from: