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Moving to uterus
Zygote moves down the fallopian tube towards the uterus after fertilisation. -
Implantation
Surges of oestrogen and progesterone from the corpus luteum prepare the endometrium to receive the blastocyst and allow the endometrium to bind with proteins on the blastocyst. Trophoblasts (outer layer of blastocyst) secrete hCG, which tells corpus luteum to keep producing oestrogen and progesterone.- happens 1 week after ovulation
- takes 5 days and finisheds within 12 days of ovulation
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Embryonic Stage
blastocyst develops into embryo which is surrounded by the amniotic sac, and differentiates into different types of cells -
Foetus develops
- 8 weeks after fertilisation
- will develop organs and grow
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Relaxin
- placenta produces progesterone, oestrogen and relaxin
- relaxin loosens joints and increases flexibility
- relaxin signals foetus to keep growing, prepares breasts for lactation, signals body to store glucose for foetus to use
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Parturition begins
- at 38 - 40 weeks
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Placenta stops producing progesterone
- progesterone was responsible to keep uterine muscles relaxed so they don't contract and stimulate labour too early.
- sudden decline in progesterone
- placenta produces cortisol, which tells placenta to produce even more oestrogen to produce for birth
- oestrogen: prepares uterus to receive new chemical signals
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Oxytocin, prostaglandins and contractions
- secreted by foetus, tells placenta to produce prostaglandin
- oxytocin and prostaglandin stimulate uterine muscles to start contracting
- when contractions get strong enough, it stimulates the release of oven more oxytocin and prostaglandin
- this positive feedback loop initiates labour