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Gametogenesis
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  • 1. Gametogenesis is a processbywhich diploid or haploidcells undergo celldivision and differentiationto form maturehaploid gametes.
  • 2.  occurs  The existence of a by meiotic division multicellular, haploi of d phase in the life diploid gametocytes cycle between into various meiosis and gametes, or gametogenesis is also by mitotic division referred to of haploid as alternation of gametogenous cells. generations.
  • 3.  theprocess of gametes formation It occurs in the gonads (ovary or testis)
  • 4. Gonial cells are the designation given togerm cells before they enter meiosis.•replicate mitotically.•genetically identical to the original zygote.•When they begin meiosis, they arecalled spermatocytes and oöcytes.
  • 5. Spermatogenesisis the process of formation of the male germcells (sperm formation).It occurs in the seminiferous tubules of thetestis.It is thread-like in shape.
  • 6. Spermatogenesis occurs from puberty to oldage, producing immense numbers of spermatozoa atan average rate of 1.5 million spermatozoa perminute.The sperm will mature in theepidiymis, nourished by sertoli cells for up to 10weeks.Humans aged 13-90 can make 1 billion sperm aday.
  • 7. The sertoli cells are supporting cells that have severalfunctions.They form the blood-testes barrier: nutrients, and circulatingsubstances do not directly reach the germ cellsThe sertoli cells determine which substances reach thegerm cells The spermatogonia are outside the blood-testis barrier.They also produce antigen-binding proteins, which arenecessary for spermiogenesis (morphological developmentof spermatids to spermatozoa).
  • 8. Spermatogenesis is the process by which male primary spermcells undergo meiosis, and produce a number of cellstermed spermatogonia, from which the primary spermatocytes arederived.Each primary spermatocyte divides into two secondaryspermatocytes, and each secondary spermatocyte intotwo spermatids or young spermatozoa.These develop into mature spermatozoa, also knownas sperm cells.The primary spermatocyte gives rise to two cells, the secondaryspermatocytes, and the two secondary spermatocytes by theirsubdivision produce four spermatozoa.
  • 9. It is an intermediary male gametogonium(a kind of germ cell).Diploid in number: 44 autosomes and 2 sex cellsIt is very small and under the process ofdevelopment.Undergoing G1-S.
  • 10. diploid in number:44 autosomes and 2 sex cellsIncreases in sizeUndergoing G2.
  • 11. Haploid in number: 22 autosomes(double stranded) and 1 sex cell each.Can see the cleavage furrowUndergoing Meiosis I (Reduction Division)Chromosomes are reduced into half number.
  • 12. Haploid in number:22 (single stranded) autosomes and1 sex cell.Undergoing Meiosis II(Equational Division)
  • 13. It is a motile sperm cell, or moving formof the haploid cell that is the male gamete.It joins an ovum to form a zygote.Matured Sperm Cell are ready tofertilized the egg.
  • 14. Oogenesis is the process of formationof the female germ cells (egg formation).It happens in the Ovary.It is Spherical in shape.
  • 15. Oogenesis begins in early foetal life.All oocytes formed in females are produced during foetal life.Many of them degenerate with time and at birth the ovariescontain about 2 million oocytes.All the oocytes go into meiotic arrest when they reach the firstmeiotic division during foetal life.The primary oocytes remain in the prophase of the first meioticdivision until the time of puberty, when they are graduallyreleased to complete meiosis at regular intervals known as theovarian cycle.On the average only one oocyte matures during eachcycle, which occurs at approximately monthly intervals, so thatthe total amount of oocytes to be ovulated is about 500 oocytes in alifetime.
  • 16. Oogonium/Oogonia