Chapter46_Gametogenesis_HormonalControl

Chapter46_Gametogenesis_HormonalControl - The Timing and...

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The Timing and Pattern of Meiosis in Mammals Differ for Males and Females Eggs provide the initial food stores for embryos For embryonic development to be successful, eggs must mature in synchrony with the tissues fo the female reproductive system that support the fertilized embryo Gametogenesis = Production of gametes Spermatogenesis = Formation and development of sperm - Continuous and prolific in adult males - Cell division and maturation occur throughout the seminiferous tubules coiled within the 2 testes **Details** - Initial or Primordial Germ Cells of the embryonic testes divide and differentiate into stem cells which mitotically divide into spermatogonia, which undergoes mitosis to form the primary spermatocytes - After meiosis I, secondary spermatocytes are formed and after meiosis II, early spermatids form which differentiate into sperm - Stem cells are situated near the outer edge of the seminiferous tubules *As sperm develops, the cells move inward *Mature sperm are released into the lumen of the tubule where it can pass into the epididymis and become motile - Sperm head contains nucleus, acrosome [contains enzymes that help the sperm penetrate the egg], and large numbers of mitochondria Oogenesis = Development of mature oocytes (eggs) - Immature eggs form in the female embryo but do not complete their develop for decades later **Details** - Oogonia are produced from the primordial germ cells - Oogonia undergo mitosis to produce primary oocytes which are arrested at prophase I - Follicle-Stimulating hormone stimulates formation of secondary oocytes (arrested at metaphase II) - Secondary oocyte is released at ovulation whn its follicle breaks open & if a sperm penetrates the oocyte meiosis II continues - The 2 meiotic divisions result in unequal cytokinesis [smaller cells = polar bodies, which degenerate] - The ruptured follicle left behind after ovulation
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This note was uploaded on 10/24/2010 for the course BIO 1101 at Cornell University (Engineering School).

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Chapter46_Gametogenesis_HormonalControl - The Timing and...

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