Steps of fertilization, where transport of gametes(oocyte and spermatozoon) , illustrated with images.
Differences in characteristics of egg and sperm of fertilization are tabulated.
Capacitation and acrosomal reaction are shown with diagrams to understand.
Barriers protecting female gamete shown with images.
Flowchart has been drawn to show the phases of fertilization and response of egg after entry of the sperm with explanation.
The result of fertilization is highlighted .
Ends
2. FERTILIZATION: is the process by which male and female gametes (an
ovum and spermatozoon) fuse to form a mono – nucleated single cell the
Zygote.
STEPS OF FERTILIZATION:
Transport of Gametes:
1). Oocyte transport: During ovulation the expelled ovum is taken up by the
ovarian fimbria, and passed to the ampulla by gentle waves of peristalsis.
2). Sperm transport: when 200 – 600 million sperms deposited on the cervix
and the fornix of vagina, sperm pass through cervical canal by movement of
their tail.
* Movement of the sperm from cervix to uterine tube occurs by their own
propulsion and assisted by movement of fluids created by cilia.
Vijaylaxmi Pattanshetti
.
FERTILIZATION
3. * Journey of spermatozoa from cervix to oviduct requires a
minimum of 2 to 7hrs.
* when reaches the isthmus, sperm becomes less motile and
stops their migration
*At ovulation, sperm again becomes motile may be because
of chemo attractants produce by cumulus oophorous cells to
reach ampulla
*Spermatozoa are not able to fertilize the oocyte , when
arrive in the female genital tract but must undergo:
(i) Capacitation and
(ii) Acrosome reaction
Vijaylaxmi Pattanshetti
4.
5. 2- SPERM TRANSPORT
** 200 – 600 million sperms
deposited on the cervix and
fornix of vagina,
** Sperm pass through cervical
canal
** Movement of the sperm
from cervix to uterine tube
takes place Vijaylaxmi Pattanshetti
9. (I). CAPACITATION:
- This step is a biochemical event.
- This is period of conditioning, lasting about 7 hours.
- Conditioning occurs in the uterine tube, having interaction
between the sperm and mucosal surface of the tube
-During this, a glycoprotein coat and seminal proteins are removed
…. from the acrosomal region by secretion of uterine glands.
-Thereby completing the capacitation and permitting acrosomal
………. reaction to occur.
Ejaculated sperm Maternal factors Capacitated sperm
Vijaylaxmi Pattanshetti
14. BARRIERS PROTECTING
THE FEMALE GAMETE
1. Corona Radiata cells
2. Zona Pellucida covering
3. Vitelline membrane of ..
…. secondary oocyte
Vijaylaxmi Pattanshetti
Vitelline membrane
15.
16. RESPONSE OF EGG AFTER THE ENTRY OF SPERMATOZOON
Vijaylaxmi Pattanshetti
1.
Cortical and
zonal reactions
2.
Resumption of
the second
meiotic division
3.
Metabolic
activation of
egg
17. THREE RESPONSE OF THE EGG AFTER THE ENTRY OF
THE SPERMATOZOON:
• 1. Cortical and Zona reaction: As a result of release of cortical oocyte
granules which contains lysosomal enzymes
a). the oocyte membrane becomes impermeable to other spermatozoa and
b). the zona pellucida alters its structure and composition to prevent more
than one sperm binding and penetration.
2. Resumption of the second meiotic division:
Oocyte completes its second meiotic division immediately after entry of
the spermatozoon.
One daughter cell known as second polar body and other is definitive oocyte
known as female pronucleus. Vijaylaxmi Pattanshetti
18. • 3. Metabolic activation of the egg:
The activation factor is probably carried by the spermatozoon.
Spermatozoon moves close to the female pronucleus and forms male
pronucleus, the tail detaches and degenerates
Both male and female pronucleus come in to close contact and loose
their nuclear envelops and form zygote.
What is parthenogenesis?
