Gametogenesis

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Gametogenesis

• To describe the process by which gametes are
  produced.

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What is Gametogenesis?

• This is the process by which sex cells are made.
• Meiosis is the production of sex cells.
• Meiosis is different in males and females.

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Spermatogenesis

• This is the formation of Sperm Cells.
• In males, each cell formed becomes a sperm cell.
• This happens by the process of meiosis in an
  uninterrupted sequence.
• The process occurs in adult males, producing as
  many as 250 400 million sperm cells in each
  ejaculation ( 5ml).

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Spermatogenesis
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OOgenesis

• This is the formation of ova or egg cells.
• Oogenesis differs from spermatogenesis in a
  number of ways.
• During the first meiotic division, cytokinesis
  is uneven, one cell takes all the cytoplasm.
• This large cell goes on to form the egg, the
  smaller cell forms polar bodies, which
  disintegrate.

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OOgenesis Cont

• At birth the ovary has all the cells it will
  ever have to develop into eggs.
• The formation of the eggs involves long resting
  periods.
• Between birth and puberty, the egg cells enlarge
  and the follicles around them grow. The primary
  egg cells replicate their DNA, they enter
  Prophase 1 but do not change again until
  reactivated by hormones at puberty.

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OOgenesis Cont

• After puberty, an egg cell stimulated by
  hormones, periodically completes meiosis 1 and
  then stops.
• This is the form in which it is released in the
  menstrual cycle.
• Penetration of the sperm cell triggers the
  second meiotic division in humans.

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OOgenesis
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Summary