Sunday, April 8, 2012

STPM Biology - chapter 14: Revision essay question 1



1. Describe the parturition process in humans. [9]

Answer:





- High level of oestrogen produced by the placenta initiates parturition

- triggers the release of prostaglandin from the uterine wall


- This enable the uterine muscle to contract

- The strong myometrium! uterine contraction sends positive feedback to mother's pituitary gland and  
   the foetus to release oxytoxin

- Both prostaglandin and oxytoxin stimulate powerful uterine contraction

- This increase in frequency as the labour progresses

- The contraction stimulates stretch receptors in the uterine wall and the cervix

- stimulate more oxytoxin to be released

- cervix dilates and soften its tissues and becoming more flexible

- The first stage of labour ends with the cervix dilating/opening to about 10 cm

- In the second stage of labour, strong contractions, aided by the mother's pushing, expel the foetus  
  through the vagina.

- The uterus contracts again and separate the placenta from the uterine wall

- The placenta is passed out and the umbilical cord is tied and cut This is the final/third stage of labour

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