The human reproduction cycle starts with the penetration of the penis into the vagina resulting in ejaculation of the sperm cellatozoonatozoa. The spermatozoon then travels up the cervix finish the uterus tract and into the ovary ducts with the help of chemotaxis quest a bend of progesterone secreted by cells surrounding the tributary oocyte, where a second-string oocyte from a graffian follicle is awaiting fertilization. Fertilization begins with the binding of a sperm belief to the glycoprotein coating of the unessential oocyte called the zone pellucida. Exocytosis of the acrosome at the tip of the sperm head releases enzymes that digest a path through the zona and enable the sperm head to bind to the plasma membrane of the oocyte, as soon as this happens the secondary oocyte goes into meiosis flag two. When the spermatozoa fuses with the zona pellicuda it disintergrates leaving only the heart and soul to demean the secondary oocyte, the secondary oocyte and the spermatozoa have 23 chromosomes each and when the heart and soul enters the secondary oocyte it is now a secondary oocyte with 46 chromosomes. short the nucleus of the successful sperm enlarges into the male pronucleus. At the uniform time, secondary oocyte completes meiosis II forming a second frigid physical structure and the distaff pronucleus, it is now known as an egg cell.
The male and female pronuclei move toward each another(prenominal) while duplicating their DNA in S phase. Their nuclear envelopes disintegrate. A spindle is formed following replication of the sperms centriole, and a undecompo sed launch of dyads assembles on it. The fe! rtilized ovum now known as the fertilized ovum is now go down for its first mitosis. When this is done, 2 cells each with a diploid set of chromosomes are formed. sectionalisation now happens which is a series of rapid mitotic divisions that subdivides the cytoplasm of the zygote into smaller, essentially equipotential cells called blastomeres contained by the zona pellucida. Cleavage generates a multicellular system essential for further...If you want to sign a effective essay, order it on our website: OrderCustomPaper.com
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