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Reproduction in Lower and Higher Animals — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYReproduction in Lower and Higher Animals5 Marks
Question
What is parturition? Which hormones are involved in parturition?
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Answer

  1. Parturition is the act of expelling out the mature foetus from the uterus of mother via the vagina.
  2. When the foetus is fully mature, it starts secreting ACTH (Adreno Cortico Trophic Hormone) from its pituitary.
  3. ACTH stimulates adrenal glands of foetus to produce corticosteroids.
  4. These corticosteroids diffuse from foetal blood to mother’s blood across the placenta. Corticosteroids accumulate in mother’s blood that results in decreased amount of progesterone. Corticosteroids also increase secretion of prostaglandins.
  5. Simultaneously estrogen levels rise bringing about initation of contractions of uterine muscular wall.
  6. Reduced progesterone level and increased estrogen level cause secretion of oxytocin from mother’s pituitary. This causes greater stimulation of myometrium of uterus.
  7. Prostaglandins cause increased forceful contraction of uterus which expels the foetus out of the uterus.
  8. Hormone relaxin secreted by the placenta makes the pubic ligaments and sacroiliac joints of the mother loosen. This causes widening of birth canal which facilitates the normal birth of the baby.

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