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Gametogenesis
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  • 1. Gametogenesis Physiology of reproductive system Ms. Beatriz Duro 3º ESO
  • 2. Human genetic material • DNA is a large molecule which coils up into a structure called chromosome when the cell is about to divide. – When the cell is not dividing it is loose in the nucleus in the form of chromatin. • DNA contains the genetic information which controls cell processes.
  • 3. Human genetic material • All human somatic cells have 46 chromosomes (23 pairs). – Diploid cells: cells with pairs of chromosomes. • Gamets have 23 chromosomes in total. – Haploid cells: cells with only one chromosome of each type. This is the human karyotype
  • 4. Human cell division Somatic cells (2n) divide to form two identical cells (2n) of the same kind through mitosis A special somatic cell (2n) divides to form four cells with half the genetic material (n) through meiosis 2 types of cell division:
  • 5. Spermatogenesis Growth and replication of DNA Meiosis Maturation
  • 6. Spermatogenesis • Maturation – Takes place in the epididymis. – The cell elongates. – The cytoplasm is reduced. – The nucleus is set at the front of the cell together with the acrosome. – The flagellum is formed.
  • 7. Male gamet: sperm
  • 8. Female gamet: ovum
  • 9. Oogenesis
  • 10. Ovarian cycle Follicular phase Caused by the secretion of FSH by the pituitary gland. Lasts 14 days Various follicles begin to develop, however only one matures Ovulation The ovum is released by the ovary. Cause by the presence of LH The body temperature increases 0.5ºC Luteal phase The area where the ovum was, tranforms into a mass of cells: corpus luteum. Corpus luteum secretes progesterone for 10-12 days. When it stops secreting hormone the cycle begins again.
  • 11. Begining of the cycle. Sharp decrease in the amount of hormones secreted by the ovaries. Vascularized uterine wall is shed and expelled from the body: period. Lasts 4-5 days Menstrual phase (Period) Uterine wall is rebuilt thanks to estrogens produced by the ovaries. Lasts 11 days. Proliferative phase Uterine lining is at its maximum thickness, ready to receive fertilised egg. Due to the progesterone secreted by the ovaries. Lasts 12 days if fertilization does not occur Secretory phase (Luteal) Uterine cycle
  • 12. Menstrual and Ovarian cycles