1. First Week of
Development

2. FERTILIZATION
• It is the process by which a sperm
units with the ovum.
•Site: It occurs at ampullary part
of uterine tube (outer 1/3 of
uterine tube)
Dr. Sherif Fahmy

3. Sperm & Oocyte
Dr. Sherif Fahmy
Corona
radiata
Zona pellucida
Cell
membrane
Secondary oocyte arrested in
2nd
meiotic division
Head
Neck
Middle
piece
Tail

4. Mechanism of Fertilization
• 1-Capacitation of the sperms.
• 2-First acrosomal reaction.
• 3-Second acrosomal reaction.
• 4- Cortical & zona reaction.
• 5- Nucleus of sperm enters the cytoplasm of
ovum.
• 6- Secondary oocyte completes 2nd
meiotic
division
• 7- Union between male and female pronuclei
to Form zygote.
Dr. Sherif Fahmy

5. FERTILIZATION
Dr. Sherif Fahmy

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Corona
radiata
Zona
pellucida

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8. Start of cortical reaction when the head of sperm starts penetration
of ovum cell membrane
Dr. Sherif Fahmy

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10. Results of Fertilization
• Formation of zygot.
• Restoration of diploid number (46
chromosomes).
• Determination of sex.
• Cleavage (segmentation) starts, during
which the zygote travels through
uterine tube by help of cilia and
contraction of uterine tube.
Dr. Sherif Fahmy

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13. 2- Cell Stage
Dr. Sherif Fahmy
Zona
pellucida

14. Artificial Fertilization:
- In vitro fertilization: Outside uterus
in culture media.
- Intracytoplasmic sperm injection.

15. Cleavage &
Migration
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16. START OF CLEAVAGE
• Fertilization leads to formation of a zygote which is
a fertilized ovum surrounded with zona pellucida.
• Zygote divides by mitotic division to form 2-cell
stage----- 4-cell stage -------- 8-cell stage ------- 16-
cell stage --------- 32-cell stage ------ 64-cell stage
(morula).
• Cells of morula are called blastomeres.
• Formation of morula takes 3 days through which it
is transmitted through the uterine tube.
• Zona pellucida prevents adhesion of zygote to
uterine tube and prevents separation of cells.Dr. Sherif Fahmy

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