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  1. 1. Gametogenesis is a processbywhich diploid or haploidcells undergo celldivision and differentiationto form maturehaploid gametes.
  2. 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. 3.  theprocess of gametes formation It occurs in the gonads (ovary or testis)
  4. 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. 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. 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. 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. 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. 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. 10. diploid in number:44 autosomes and 2 sex cellsIncreases in sizeUndergoing G2.
  11. 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. 12. Haploid in number:22 (single stranded) autosomes and1 sex cell.Undergoing Meiosis II(Equational Division)
  13. 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. 14. Oogenesis is the process of formationof the female germ cells (egg formation).It happens in the Ovary.It is Spherical in shape.
  15. 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. 16. Oogonium/Oogonia