third wk there is formation of three germ layers. primitive streek and prochordal plate forms the intra embyyonic mesoderm. the epiblast cells replace all the 3 germ layers. iem is converted to paraxial, intermediate and lateral plate mesoderms

1. General anatomy test 2
Marks:5
5X1=
5
1. What is a primordial follicle?
2. Which hormone induces follicular
phase of the ovarian cycle?
3. When does LH surge occur?
4. What is the function of the corpus
luteum?
5. Name the phases of menstrual cycle?

2. 1stweek of
development

3. FALLOPIAN
TUBE
• 2 openings
– Abdominal
ostium
– Uterine ostium
• 4 Parts
– Infundibulu
m
– Ampulla
– Isthmus
– Intra-mural

4. 1st week of
development
1. Transport of
gametes
2. Fertilization
3. Cleavage
4. Blastocyst
formation
5. Implantation

5. Transport of
gametes
Oocyte transport
– During ovulation, the secondary oocyte is
released
– The fimbriated end of the uterine tube comes
close to the ovary and “sweep” the secondary
oocyte into the funnel-shaped infundibulum
Oocyte
lifespan:
24 hours

6. Structure of ovum after
ovulation
Corona radiata
First polar body
Secondary
oocyte
Perivitelline
space Zona
pellucida

7. Transport of
Spermatozoa
• 200- 300 million deposited in the vagina
• Only 1% enter the cervix
• It takes about 2-7 hours to reach the fallopian
tube
Incapable of fertilization until:
1. Capacitation
2. Acrosome reaction

8. 1. Capacitation (7
hrs)
• Period of conditioning in the female genital
tract (mainly in uterine tubes)
• Glycoprotein coat and seminal proteins are
removed from the surface of acrosome
• No morphological changes

9. Effects of
Capacitation
1. Increases sperm motility
2. Destabilises acrosomal membrane and
allows it to penetrate outer layer of egg.

10. Acrosome
reaction
• When the capacitated sperms binds to the
zona pellucida, acrosome reaction is
induced by zona proteins.
• This is associated with the release of
enzymes, including hyaluronidase and
acrosin
Sperms lifespan:
4 days in the female genital tract

11. Acrosome
reaction
• Sperm head makes
multiple contacts
between plasma
membrane and outer
membrane of acrosomal
cap and liberate enzymes
to overcome the barriers
around oocyte

12. 2. Acrosome
reaction

13. Fertilization(Day
1)
• Begins with contact
between
spermatozoa and
secondary oocyte
• Fertilization occurs
in the ampulla of
the uterine tube
• Many
spermatozoa
reach the site of
fertilization
• Only one fertilizes
the
secondary
oocyte
Fertilization
in ampulla

14. PHASES OF
FERTILIZATION
1. Penetration of
the corona
radiata
2. Penetration of
the Zona
Pellucida
3. Fusion of oocyte and
sperm cell

15. 1. Penetration of the corona
radiata
• Only capacitated sperm can penetrate
corona radiata and undergo acrosome
reaction
• Dispersal of corona radiata cells
– Hyaluronidase enzyme released
from the acrosome

16. 2. Penetration of the Zona
Pellucida
• Zona pellucida is
a glycoprotein
shell
• It facilitates sperm
binding and induces
the acrosomal
reaction
• Acrosomal
enzymes: Acrosin

17. ZONA
REACTION
When the head of
the sperm
contacts the
oocyte surface:
•Cortical granules
lining the plasma
membrane of the
oocyte release
lysosomal enzymes
•Permeability of the
zona pellucida
changes to prevent

18. 3. Fusion of oocyte and
sperm cell
membranes
• The sperm head and tail enter into the
oocyte
• plasma membrane remains attached to
oocyte surface

19. Entry of sperm inside the secondary oocyte
results
in
1. Completion of the second meiotic division
2. The second polar body is extruded
3. Nucleus of the mature oocyte becomes the
female pronucleus
4. The head of the spermatozoa forms the
male pronucleus

20. Pronucleus:
Male (22+X or
22+Y),
Female (22+X)
• The pronuclei lose their
nuclear membranes and
mixing of chromosomes
occurs
• Finally large cell
Zygote is formed
(44+XX or 44+XY)

21. Results of
Fertilization
• Restoration of diploid number
of chromosomes(46)
• Determination of the sex of new
individual
• Initiation of cleavage

22. Cleavage (Day
2)
• 2 cell stage embryo is formed by mitotic division of
zygote
• Once the zygote has reached the two-cell
stage, it undergoes a series of mitotic
divisions
• Divided embryonic cells are called blastomeres.
These cells are covered by zona pellucida
2- 4- 8-
compacti
on
16-

23. COMPACTI
ON
After 8 cell stage they tightly align against each
other to form a compact ball of cells .
Compaction, segregates inner cells, which
communicate extensively by gap junctions, from
outer cells

24. Morula (Day
3)
• Mulberry
appearance
16- cell
stage
PLACEN
compacti
on

25. Blastocyst
formation
• The morula enters the uterine cavity on the 4th day
after fertilization
• Fluid enters into the morula from the uterine cavity
and it
acquires the shape of a cyst and is called the
Blastocyst
• The cavity of the blastocyst is called Blastocoele
• Early blastocyst Late blastocyst

26. Late
Blastocyst
Abembryonic
•Zona pellucida disappears followed by the cells of
the trophoblast are flattened
•Inner cell mass are attached to the trophoblast on
one side only. This side is called Embryonic pole
• The opposite side is called the Abembryonic
pole
Embryonic pole
Blastoce
le

27. Trophoblast & Zona
pellucida
• The trophoblast is sticky in nature
• The zona pellucida prevents the embryo
from sticking to abnormal sites before it
reaches into uterine cavity
• Thus the zona pellucida disappears at
day 5 when the blastocyst reaches
uterine cavity and allows for
implantation

28. IMPLANTATI
ON
• The process by which
the trophoblast of the
blastocyst sticks and
invades the
endometrium
• Implantation begins
on
Day 6 after
fertilization
• The normal site for
implantation is the
fundus posterior wall of
Normal site of
implantation

29. • Embryonic pole of Blastocyst attaches
to the stratum compactum layer
• Trophoblast proliferates and produce finger-
like processes to invade the endometrium
IMPLANTATI

30. DECID
UA • Functional layer
of endometrium
in a pregnant
woman
• D.basalis – part of
decidua deep to the
conceptus that forms
the maternal part of
placenta
• D.capsularis –
superficial part of
decidua overlying the
conceptus
• D.parietalis – all the
remaining part of

31. • In response to increasing progesterone
levels in the maternal blood, cells of
decidua enlarge to form pale staining
decidual cells, they enlarge as glycogen
and lipids accumulate in their cytoplasm
• Cellular and vascular changes occurring
in the endometrium as the blastocyst
implants constitute the decidual reaction

32. Summary of 1st
wk

33. Ectopic
pregnancy

35. Assisted Reproductive
Technology
1. In Vitro Fertilization(IVF)
2. Intracytoplasmic sperm
injection(ICSI)
3. Artificial insemination
4. Gamete intrafallopian
transfer(GIFT)
5. Zygote intrafallopian

36. APPLIED
IMPORTANCE
• In vitro
fertilization (IVF)
and Embryo
transfer
• IVF of oocytes and
transfer of cleaving
zygotes into the
uterus
• Done in sterile
women having tubal
block

37. In vitro fertilization (IVF)
and Embryo transfer -
Steps • Ovarian follicles are
stimulated
by giving gonadotropins
• Mature oocytes aspirated by
laparoscopy and by
ultrasound guided large
gauge needle through
vaginal wall
• Oocytes placed in a
Petridish with special
culture medium and
capacitated sperms
• Fertilization and cleavage
monitored microscopically
• 4 embryos having 4-8 cell
stage transferred by
catheter to uterus
• Supine position

38. APPLIED
IMPORTANCE
• Cryopreservation of Embryos
– Early embryos from IVF are
preserved for longer periods
by freezing with
cryoprotectant (glycerol).
After thawing they are
successfully transferred to the
uterus.

39. APPLIED
IMPORTANCE
• Intracytoplasmic Sperm Injection (ICSI) –
Sperm is directly injected in to the
cytoplasm of mature oocyte. Used in
couples where IVF failed or in male
infertility with oligospermia.

40. APPLIED
IMPORTANCE
• ZIFT (Zygote Intra Fallopian
Transfer)

41. GIFT (Gamete Intra Fallopian
Transfer). Involves super
ovulation, oocyte retrieval, sperm
collection, laparoscopic
placement of several oocytes and
sperms in to the fallopian tubes.
Fertilization occurs in the ampulla

43. THANK
YOU