A small unit done by myself and two fellow students in my lecture class - UK.ANJUM and L.LINDEQUE

1. EMBRYONIC DEVELOPMENT
AFTER FERTILIZATION
DONE BY
UK.ANJUM
L.LINDEQUE
S.VENKETAS

2. 3 PROCESSES OCCURE IN AN
EMBRYO AFTER FERTILIZATION:
1) Cleavage
2) Gastrulation
3) Organogenesis

3. Cleavage

4. CLEAVAGE
• A period of rapid cell division without growth.
• A hollow ball of cells are formed called a
blastula.
• The blastula consist of many smaller cells called
blastomeres.
• The blastula has a hollow part that is filled with
fluid and is called a blastocoel.

5. EARLY EMBRYONC DEVELOPMENT
IN ANIMALS

6. BLASTOMERES

7. TWO TYPES OF CLEAVAGE
1) Meroblastic cleavage – this is the incomplete
division of the egg. This occurs in species with
yolk-rich eggs such as reptiles (insects, frogs,
fishes) and birds.
This happens in these eggs due to the large
volume of yolk as it slows or blocks some of the
cuts, therefore fewer divisions of the yolky part of
the egg.

8. 2) Holoblastic cleavage – this is the complete
division of the egg. This occurs in species whose
eggs have little amounts of yolk, such as sea
urchins and frogs. (sea stars and mammals)
Here the cuts slice right through the nearly
yolkless eggs.

10. GASTRULATION

11. GASTRULATION
Gastrulation is an early embryonic
development in which the cells of a
blastula rearranges into a three-layered
embryo, called a gastrula.

12. THREE EMBRYONIC GERM LAYERS
•Ectoderm
•Endoderm
•Mesoderm

13. ECTODERM
• Ectoderm is the outer layer of the developing
embryo.
It gives rise to:
• Integumentary system
• Brain
• Spinal cord
• Pituitary gland

14. ENDODERM
• Endoderm is the innermost (internal) layer found
in a developing organism.
It gives rise to:
• Epithelial layer of lungs
• Digestive system
• Liver
• Pancreas
• Bladder
• Thyroid glands

15. MESODERM
Mesoderm is the middle layer of the
developing embryo. It is found between
the ectoderm and the endoderm.

17. ORGANOGENESIS

18. ORGANOGENESIS
• Organogenesis is the process of the ectoderm,
endoderm and mesoderm developing into internal
organs of an organism.
• Endoderm: Form tissues within the lungs , thyroid
and pancreas.
• Mesoderm: Assists in the production of cardiac
muscle, skeletal muscles, smooth muscles , tissues
within kidneys and red bloody cells.
• Ectoderm: Makes tissues in the epidermis and
helps in the formation of neurons in the brain and
melanocyte.

20. ORGANOGENESIS CONTINUED….
• In every vertebrates the mesoderm forms the
notochord and the ectoderm forms the neural
plate.
• The neural plate folds inwards and forms a
neural tube which will further go to form the
central nervous system which is the brain and
the spinal cord.

21. FORMATION OF NEURAL CORD
FROM NEURAL PLATE

22. Embryonic development process