GAMETOGENESIS

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GAMETOGENESIS
Dr. Ahmed Fathalla Ibrahim
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MITOSIS
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DIFFERENCE BETWEEN MITOSIS MEIOSIS
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DEFINITION

• The process of formation of mature male female
  gametes.
• Spermatogenesis sequence of events by which the
  primitive germ cells (spermatogonia) are
  transformed into mature sperms or spermatozoa
• Oogenesis sequence of events by which the
  primitive germ cells (oogonia) are transformed
  into mature oocytes

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SPERMATOGENESIS

• AIM formation of sperms with haploid number of
  chromosomes
• SITE in the seminefrous tubules of testis
• DURATION takes about two months
• OCCURRENCE starts at puberty continues
  throughout life

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SPERMATOGENESIS
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SPERMATOGENESIS

• STAGES
• PROLIFERATION each spermatogonium divides by
  mitosis into 2 daughter spermatogonia (with
  diploid number of chromosomes 44 XY)
• GROWTH spermatogonium enlarges to form a primary
  spermatocyte (with diploid number)
• MATURATION (BY MEIOSIS)
• 1st meiotic division a reduction division by
  which a primary spermatocyte divides into two
  secondary spermatocytes (haploid number of
  chromosomes 22 X or 22 Y)
• 2nd meiotic divison a process of mitosis without
  a normal interphase (without DNA replication)
  through which a secondary spermatocyte divides
  into two spermatids (with haploid number of
  chromosomes)
• SPERMIOGENESIS a process by which a spermatid is
  transformed into a mature sperm (with haploid
  number)

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SPERMIOGENESIS
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SPERM
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SEMINAL FLUID

• SOURCE secretions from seminal vesicles,
  prostate gland bulbourethral glands
• VOLUME 3 5 ml
• SPERM COUNT about 100 millions/ml
• MOTILITY about 3mm/min, at least 70 of sperms
  should be motile
• ABNORML FORMS should not exceed 10

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OOGENESIS

• AIM formation of secondary oocytes with haploid
  number of chromosomes
• SITE in the cortex of ovary
• OCCURRENCE starts during fetal life , becomes
  completed after puberty continues till menopause

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OOGENESIS
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OOGENESIS

• STAGES
• DURING FETAL LIFE
• Proliferation each oogonium divides by mitosis
  into 2 daughter oogonia (with diploid number of
  chromosomes 44 XX)
• Growth oogonium enlarges to form primary oocyte
  (with diploid number). Primary oocytes begin 1st
  meiotic division stop at prophase
• DURING EACH OVARIAN CYCLE (AFTER PUBERTY)
• 1st meiotic division is completed a reduction
  division by which a primary oocyte divides into
  one secondary oocyte (haploid number of
  chromosomes 22 X) 1st polar body
  (degenerates)
• 2nd meiotic divison begins begins at ovulation,
  progresses only to metaphase and becomes arrested
• AFTER FERTILIZATION (IN THE FALLOPIAN TUBE)
• 2nd meiotic division is completed 2ry oocyte
  divides into one mature ovum (haploid number)
  2nd polar body (degenerates)
• N.B. NO PRIMARY OOCYTES FORM AFTER BIRTH IN
  FEMALES

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OVULATION
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