Model on Fertilization in human beings
2 minute read
Good Morning everyone,
Today I --- going to tell about the fertilization in humans
Fertilization is the epic story of a single sperm facing incredible odds to unite with an egg and form a new human life is the story of all of us.
During sexual intercourse about 300 million sperm enter the vagina, soon afterward million of them will either flow out of the vagina or die in its acidic environment.
remaining sperms passes through the cervix and the opening into the uterus
Inside the uterus muscular uterine contraction assist the sperm on their journey Towards the egg.
However resident cells from the womens immune system mistaking the sperm for foreign invaders,destroy thousands more
Next half the sperms head for the empty fallopian tube while the other half swim towards the tube containing the unfertilized egg released during ovulation
now
only a few thousand remain
Inside the fallopian tube tiny cilia pushed the egg towards the uterus
To continue the fertilization must surge against this motion to reach the egg
only few dozen of the original 300 million sperm remain the egg is covered with a layer of cells called the corona radiata the sperm must pushed through this layer to reach the outer layer ot the egg the zone pellucida
when sperm reached the zona pellucida they attach to specialized sperm receptors on the surface which triggers their acrosomes to release digestive enzymes enabling the sperms to burrow into the layer
inside the zina pellucida is a narrow fluid field space just outside the egg cell membrane
The first cell to make contact will fertilised the egg after a perilous journey and against incredible odds a single sperm attaches to the egg cell membrane
within a few minutes their outer membranes fuse and the egg pulls the sperm inside
this event cause changes in the egg membrane that prevent other sperm for attaching to it
next the egg releases the chemicals that push other sperm away from the egg
As the reaction spreads outwords the zona pellucida hardens trapping any sperm unlucky enough to be caught inside
outside the egg,sperm are no longer able to attach to the zona,pellucida
Meanwhile inside the egg the tightly packed male genetic material spreads out a new membrane forms around the genetic material creating the male pronucleus
inside the genetic material regorms into 23 chromsomes
the female genetic material awakened by the fusion of the sperm with the egg finishes dividing
resulting in the female pronucleus which also contains 23 chromosomes
as the male and female pronuclei form spider web - like thresds called Microtubules pull them towards each other
the two sets of chromosomes joined together
completing the process of the fertilization at this moment a unique genetic code arises instantly determining gender,hair color,eye color and hundreds or other characheristics
this new single cell the zygote is the beginning of a new human being.
and now the celia and the fallopian tube gently sweep the zygote towards the uterus where he or she implant in the richer uterine lining growing and maturing for the next nine months until ready for birth
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