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Comparative Vertebrate Physiology

Comparative Vertebrate Physiology. Fertilization and nurturing of the embryo and young. Fertilization. Sequence of events Sperm capacitation Acrosomal enzymes weaken oocyte membrane Sperm nucleus and centriole penetrates into the ovum Monospermy is assured by:

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Comparative Vertebrate Physiology

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  1. Comparative Vertebrate Physiology Fertilization and nurturing of the embryo and young

  2. Fertilization • Sequence of events • Sperm capacitation • Acrosomal enzymes weaken oocyte membrane • Sperm nucleus and centriole penetrates into the ovum • Monospermy is assured by: • Entry of extracellular Na+ reversing oocyte membrane polarity • Ca++ causes cell to prepare for cell division • This cortical reaction destroys sperm receptors on plasma membrane

  3. Reproductive synchrony • Development/release of gametes from male and female done simultaneously • e.g. development of bird testes • Environmental cues (temp., day length)

  4. Hormones • Viability of the corpus luteum maintained by hCG • Levels of estrogen and progesterone rise due to secretionby the placenta • Estrogen and progesterone levels rise in anticipationof birthing and lactation

  5. Birthing • Involuntary contractions of uterine smooth muscle (positive feedback)

  6. Birthing • Amniotic sac pushes up against cervix wall (“breaking of water”) • Birth follows • Further uterine contraction expels the placenta

  7. Lactation • Rising estrogen and progesterone levels stimulate release of PRH • Lactogenesis • Colostrum is the first milk • Humans: little fat, mostly protein, vitamins, antibodies • Marine mammals: 58% fat in seals

  8. Milk let down reflex • Positive feedback (galactopoiesis)

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