Fertilization Process in Human (Internal Fertilization)

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1. selfexplanatory.2022
HelloHI
नमस्ते
ْم
ُ
كْيالاع ُمالََّسلا
َِّللَّٱ ُةامْحاراو
ُهُتاكاراباو
Saba Parvin Haque
M.Sc. Life Sciences
(Specialization in Neurobiology)
from “Sophia College”
(Autonomous), Mumbai.

2. Saba Parvin Haque

3. Source: (Alves et al., 2020)
FERTILIZATION
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4. TYPES OF FERTILIZATION?
https://media.geeksforgeeks.org/wp-content/uploads/20240227102908/Internal-Fertilization.png
https://tlprodfilesmum.s3.ap-south-1.amazonaws.com/UploadLinks/UploadLinks_Slide6JPG2020_01_21_11_21_31_PM.JPG
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5. INTERNAL VS EXTERNAL FERTILIZATION
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6. AFTER FERTILIZATION THERE ARE
POST FERTILIZATION EVENTS.
Oviparous
❑Lay egg outside female body after fertilization
E.g. Reptiles, Birds
❑Egg laying Mammals: Monotremes (platypus,
Echdina) (link between Reptiles & Mammals)
❑Egg large having sufficient nutrient required for
development of embryo
❑Clutch size- Large
❑Protection of egg/embryo required
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7. AFTER FERTILIZATION THERE ARE
POST FERTILIZATION EVENTS.
Viviparous
❑Fertilize egg is retained within female
reproductive tract
❑Embryo development occurs with
uterus/womb
❑Live bearing/birth E.g. Mammals
❑Placenta
•Nutrient exchange
•Gas exchange
•Waste material exchange
❑Clutch size small
❑Embryo remain protected in female body
❑Proper incubation temperature
https://images.app.goo.gl/zk8yu3gx1Fdjz4hR6https://images.app.goo.gl/fYuBrocgGFGtVyHy7Saba Parvin Haque

8. ❑Fertilized egg is retained in female
body but nourishment is obtained
from egg itself
❑Example - Shark, Anaconda snake
❑Live birth
❑Embryo remain protected in female
body Proper incubation temperature
AFTER FERTILIZATION THERE ARE
POST FERTILIZATION EVENTS.
OvoViviparous
https://images.app.goo.gl/ZVwJX6cUAdquHoU78, https://images.app.goo.gl/x4mZ4Ej51dkMKbbQ8
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9. AFTER FERTILIZATION THERE ARE POST FERTILIZATION EVENTS
On basis of location of post fertilization embryo development.
https://microbenotes.com/wp-content/uploads/2020/08/Differences-Between-Oviparous-and-Viviparous.jpeg
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10. AFTER FERTILIZATION THERE ARE POST FERTILIZATION EVENTS
On basis of location of post fertilization embryo development.
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11. Internal Fertilization (Human)
Difficulties:
1. Fertilization occurs in oviduct - difficult to study
2. Released sperms are at different stage of maturation
3. There can be multiple ways of acrosomal reactions?
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12. 1.Capacitation - Ampulla of oviduct
2.Movement of sperm toward egg
1.Thermotaxis
2.Chemotaxis
3.Rheotaxis
3.Entering of sperm into cumulus
4.Acrosomal reaction within cumulus
5.Binding of sperm to Zona pellucida
6.Species specific interaction
•Sperm recognize - ZP2 protein
EVENTS DURING FERTILIZATION
7.Fusion of sperm plasma membrane to
egg plasma membrane
•Izumo- Juno and CD9 protein
8.Block to polyspermy
•Fast block Absent
•Slow block - Calcium mediated
9.Activation of egg
10. Resumption of meiosis-II
11. Egg metabolic activation
12. Fusion of genetic material
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13. 1.CAPACITATION
Occurs within female reproductive system Final maturation of sperms - capable to fertilize eggAmpulla of oviduct
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14. ❑Major changes in sperm during
capacitation
•Removal of cholesterol by albumin protein
•Specific protein on sperm surface are lost
(These proteins block recognition site of
the sperm protein to ZP)
❑K+ efflux
•K+ ions are transported outside from
sperm head.
•Membrane potential become more negative
❑Increase calcium permeability
•Calcium influx (It makes immature sperm
to mature so as to fertilize with ovum)
•HCO
3 ions and other ions influx sperm.
1.CAPACITATION
Soluble adenylyl
cyclase (SACY)
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15. 1.CAPACITATION
Soluble Adenylyl
Cyclase (SACY)
•Increase of cytosolic pH (HCO
3
-
) (7.2
to 7.4)
•Increase fibronectin expression = ↑
•Effect of increase of cytosolic calcium
and pH of sperm
•Increase dynein activity,
-----sperm molecular motor (ATP)
-----Associated with microtubule which
form axoneme in sperm tail
•Hyper-activation of sperms
•Sperm rapidly migrate toward egg
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16. •Sperm flagellar motility (Dynein - ATP)
•Uterine muscle contraction
•Thermotaxis: Heat sensing; a thermal gradient
of 2ºC between the isthmus of the oviduct and
the warmer ampullary region
•Chemotaxis: Progesterone, CRISP1 sensing
(rabbit)
•Sperm rheotaxis: Negative
•cues from the flow of liquid from the oviduct to the
uterus
•Migrate against the direction of the flow-using
CatSper calcium channels (calcium transporter
sperm).
2.MOVEMENT OF SPERM TOWARD EGG
Fluid Down
Sperm Up
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17. 3.ENTERING OF SPERM INTO CUMULUS
❑Follicle cells which
are loosely associated
are cumulus
•→ sperm move
through interstial
space
•→flagellar motion
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18. •JIN AND COLLEAGUES
•Fuso genic protein on
acrosomal membrane
•Acrosomal membrane
fuses with sperm plasma
membrane
•Enzymes are released&
Acrosomal Content is
released
•Digestion of component
of Zona pellucida &
matrix of cumulus
4.ACROSOMAL REACTION OCCUR WITHIN CUMULUS PRIOR TO
BINDING TO ZONA PELLUCIDA
2.Binding to Zona Pellucida
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19. Pathway 1: Acrosomal
reaction prior to
interaction with zona
pellucida, occurs in
cumulus (Major 90%)
Pathway 2: Acrosomal
reaction occur after
interaction of sperm with
2P3 protein of zona
pellucida (Minor 10%)
4.ACROSOMAL REACTION OCCUR WITHIN CUMULUS PRIOR TO
BINDING TO ZONA PELLUCIDA
2.Binding to Zona Pellucida
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20. 5.BINDING OF SPERM TO ZONA PELLUCIDA
Fastest runner reached to Egg
(5) Entry Into Perivitelline Space
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21. 6.SPECIES SPECIFIC INTERACTION
❑Sperm recognize ZP2 protein
❑Gain of function experiment:
•Transgenic mouse oocyte were constructed
•They are expressing mouse zona protein and
one of four human zona protein
•Human sperm binds to mouse oocyte
expressing ZP2 protein
❑Sperm: ZP2 receptor
❑Zona Pellucida: ZP2 Protein
❑Rat: ZP1, ZP2, ZP3
❑Human: ZP1, ZP2, ZP3, ZP4
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22. •Equatorial region fusion
•Izumo-immunoglobulin like protein
interacts with
•Juno protein
•CD9 Protein
7.FUSION OF SPERM PLASMA MEMBRANE TO EGG
PLASMA MEMBRANE
https://images.app.goo.gl/aeVkkdZ56iLW6Xda6
https://images.app.goo.gl/7TqPBK6eUBJU1mzv5
Nucleus &
Centriole will
enter in ovum
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23. •Fast block - Absent
•Slow block - Calcium ion
mediated (start with a minute of
sperm interaction)
•Slow/late/permanent block to
polyspermy
•After first sperm interaction
•Cytosolic Ca
2+
increases, release
from ER
8.BLOCK TO POLYSPERMY
Fertilization
(7) cortical reaction, and (8) block to polyspermy.
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24. ❑Role of increased cytosolic Ca
2+
ion
•Activation of CAM kinase
•Synaptotagmin activation (SNARE
protein vesicle fusion with plasma
membrane)
•Release of ovastacin from cortical
granules
•Ovastacin removes ZP2 protein from
zona pellucida (NO more sperms can
interact)
•Loss of function in Ovastacin
(mutation)
•No removal of ZP2 protein
•Polyspermy can occur
8.BLOCK TO POLYSPERMY - CA
2+
ION
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25. ❑Release of zinc ions (efflux) after entry of first sperm
❑Zinc binds to zona pellucida (Zinc shield)
❑Zinc inhibit acrosomal enzymes acrosin and MMP2 (Digestion of zona
pellucida) as well as enzyme necessary for capacitation (No more
capacitation)
8.BLOCK TO POLYSPERMY - THE ZINC SPARK
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26. 8.BLOCK TO POLYSPERMY – JUNO PROTEIN
❑Juno protein is released from oocyte cell membrane
•Soluble juno binds to free sperm in peri-vitelline space
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27. ❑Fusion of membranes
❑Release of PLC-Zeta from sperm head
❑PLC-Zeta enters egg cytosol
❑PIP2 → DAG + IP3
❑IP3 allow release of calcium from ER to
cytosol
❑Ca
2+
activates calmodulin activated
protein kinase (CAM Kinase)
❑Removes inhibitors of mRNA
translation
•mRNA translation allowed
9.ACTIVATION OF EGG
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28. •Egg is released arrested at
metaphase II
•Cytostatic factor (Mos) APC ---
(Do arrest)
•Ca
2+
--- CAM kinase inhibit Mos --
- APC Active
•Meiosis II resumption
(Male nucleus has came so female should also complete
her meiosis 2)
10.RESUMPTION OF MEIOSIS II
Anaphase
Promoting
Complex
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29. •Multiple series of Ca2+ waves generated
•Increase in protein synthesis
•Increase in respiration rate
11.EGG METABOLIC ACTIVATION
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30. ❑Sperm nucleus – Highly condensed/compact
•Protamines
•Highly basic protein
•High disulphide bond
❑Reduced Glutathione - Present in egg
cytosol
•Breaks disulphide bonds
❑Protamine are removed & replaced by
normal histone
❑Uncoiling of sperm chromatin
Euchromatin
❑Fusion of genetic material occurs
12.FUSION OF GENETIC MATERIAL
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31. 12.ZYGOTE FORMATION
https://images.app.goo.gl/eCvG6yRCn2GMjcL27
Each nucleus enters into
G1, S, G2 & M phase
https://images.app.goo.gl/JG6NPZTPckvuorYZ8
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32. •Normal fertilization and implantation. (2015b, April 10). Clinical Gate.
https://clinicalgate.com/normal-fertilization-and-implantation/
•https://teachmephysiology.com/reproductive-system/pregnancy/conception/
•https://www.geeksforgeeks.org/internal-fertilization/
•https://images.app.goo.gl/WvLdfq9zD7LUkL1e6
•https://images.app.goo.gl/YE2kVtDYzbHypPT66
•https://images.app.goo.gl/ZSfL9CQpPEW7V8df8
REFERENCES
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