pregnancy

• • Also known as gestation is period of reproductive from blastocyst implanting in uterus and foetus leaving uterus at birth
• • After 8 weeks developing organism has distinct features and known as foetus
• • Following implantation of blastocyst, rapid cell differentiation and specialization occur giving rise to embryo
• • Once implanted in uterine wall, developing placenta surrounding embryo begins to release hormone human chorionic gonadotropin to signal women is pregnant and stop menstruation
• • hCG sustains corpus luteum in first 3 months of pregnancy allowing it to continue secreting oestrogen and progesterone
• • After 3 months, corpus luteum breaks down once placenta has fully developed and takes over as endocrine organ of pregnancy→ hCG levels decrease
• • Once fertilized egg implanted into uterine wall, initiates formation of placenta which is formed by maternal and foetal tissue
• • Role of placenta includes:
  • Exchange of nutrients, oxygen and removal of wastes between mother and foetus through diffusion as no exchange of blood
  • Producing hormones oestrogen and progesterone to maintain pregnancy
• • Progesterone is required at high levels throughout pregnancy with levels steadily rising until birth of the baby. Maintains uterine lining endometrium immediately after implantation to nourish embryo until placenta formed. Throughout pregnancy prevents lactation and uterine contractions until foetus fully developed and ready for birth
• • Oestrogen levels steadily rise throughout pregnancy to prevent ovulation during pregnancy, promote organ development in foetus and promote development of mothers breast tissue in preparation for lactation after birth