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  1. #1
    Roxanita is offline Senior Member
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    Embryo: What kind of Gametes are present at birth?

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    What kind of Gametes are present at birth?

    Males:
    In testes: PGC has basically migrated into and are the only gamete formed cells found in the testes at birth.
    Those PGC are gonna remain dormant until PUBERTY and then they are gonna begin Spermatogenesis by converting:
    Type A Spermatogonia --> into Type B Spermatogonia

    Spermatogenesis is gonna proceed in waves through Meiosis I and Meiosis II

    What is formed at the end of meiosis II?
    Spermatids (haploid)

    Spermatogenesis
    Primary Spermatocytes from two secondary spermatocytes.
    Secondary spermatocytes form two spermatids.
    Spermatids undergo spermiogenesis, which is series of morphological changes resulting in the mature sperm.



    FEMALES:

    In Contrast Oogenesis begins much earlier, remember that Primordial germ cells PGC migrate into the Indifferent Ovary and differentiate into Oogonia but this happen in Week 4 in Uter.
    Also in Utero, the Oogonia begins Meiosis I by forming Primary Oocyte but they do not complete Meiosis I in Utero. All primary Oocytes are formed by month 5 of fetal life, they remain arrested in Prophase of MEIOSIS I


    What kind of Gametes are present at birth in females?
    At birth there are no PGC in ovary unlike the male testes and there are no Oogonia in the ovary present at birth; what is present at birth in the female Ovary are Primary Oocyte that are arrested in the Prophase stage of Meiosis I, they remain arrested until Puberty when according to the menstrual cycle a Primary Oocyte will complete Meiosis I and form a Secondary Oocyte and a extruded Polar Body.

    The Secondary Oocyte just prior to Ovulation will have begun Meiosis II but will have not completed it b/c it will become arrested in Metaphase of Meiosis II just prior to Ovulation



    What is Ovulated?
    A Secondary Oocyte is extruded to the wall of the ovary. The Secondary Oocyte will only complete Meiosis II when fertilization occurs which occur typically in Uterus.


    Oogenesis
    Primordial germ cells arrive in the indifferent gonad at wk 4 and differentiate into oogonia.
    Oogonia enter meiosis I to form primary oocytes. All primary oocytes are formed by month 5 of fetal life and remain arrested in prophase (diplotene) of meiosis I until puberty.
    No oogonia are present at birth.

  2. #2
    samgeorgy is offline Newbie 510 points
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    I HATE YOU EMBRYO!!! My mortal enemy!

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