 Cleavage
 Morula
 Blastocyst
 Implantation
 Occurs
in the
ampulla of the
uterine tube.
 Capacitation

Period of conditioning in the female reproductive tract
– lasts approximately about 7 hours.

Occurs in the uterus or uterine tube .

Epithelial interaction between the sperms and mucosal
surface of the genital tract.
 Acrosome

reaction
Release of the enzymes needed to penetrate the zona
pellucida.
3
4
 DEFINED
 Complex
AS…….
sequence of cordinated molecular
events that begins with contact between a
sperm and an oocyte and ends with the
intermingling of maternal and paternal
chromosomes .
 The
fertilization process takes approximately
24 hours.
 Passage
of sperm through corona radiata
ENZYME- HYALURONIDASE
 Penetration
of the zona pellucida by the sperm
 ACROSIN
ZONA REACTION-LYSOSMAL ENZYMES
 Fusion
of oocyte and sperm cell membrane.
 Completion
of the second meiotic division
of the secondary oocyte and formation of
female pronucleus.
pronucleus
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 Formation
of the male pronucleus
Oocyte containg two haploid pronuclei is called as Ootid.
Union of male and female pronucleus
Splitting of 23 paternal and 23 maternal
Chromosomes
Division of cytoplasm
Formation of two celled structure called the Zygote
 Restoration
of diploid chromosomal number
 Bi-parental
inheritance
 Primary
sex determination
 Initiation
of the cleavage of the zygote
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Two celled zygote
 Mitotic divisions
 Cells are called blastomeres
 Clevage normally occurs as the zygote passes along the
uterine tube towards the uterus
 Morula
 Inner cell mass – embryo proper
 Outer cell mass – Trophoblast - Placenta

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 Morula
enters the uterine cavity
 Development of blastocele
 Formation of blastocyst
 Cells of the inner cell mass – Embryoblast
 Cells of the outer cell mass – Trophoblast
 Zona pellucida disappears.
 End of first week of development
Beginning of the Implantation
(Penetration of the uterine wall)

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



6 days after fertilization
(day 20 of a 28 day
menstrual cycle),
blastocyst attaches to to
the endometrial
epithelium.
Trophoblast differntiates
in to 2 layers:
Inner layer of
cytotrophoblast
Outer layer of
syncytiotrophoblast
6th day – syncytiotrophoblast extend through the
endometrial epithelium and invade the
connective tissue .
 By the end of first week ,blastocyst is
superficially implanted in the compact layer of
the endometrium .
 Syncytiotrophoblast produces enzymes that
erode maternal tissues enabling the blastocyst to
burrow in to the endometrium.
 At 7th day , a layer of cells ,the hypoblast
(primary endoderm), appears on the surface of
the embryoblast facing the blastocystic cavity.

 Begins
at fertilization
 Several changes take place before fertilization:
Gametogenesis
 Formation of zygote
 Cleavage
 Blastocyst formation
 Penetration of endometrial stroma
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