Birth

• Parturition


  Giving birth
• Childbirth, or labour, is preceded by a rise in the levels of oestrogen and oxytocin in the mother's bloodstream

  
• Labour


  1. Begins with contractions

  2. Contractions start at the top of the uterus

  3. Contractions sweep down to the cervix

  4. Contractions become stronger and more frequent
• Three stages of labour

  • Dilation
  • Expulsion
  • The placental stage
• Dilation


  1. Contractions force the baby’s head into the cervix

  2. Stretching until the head enters the birth canal

  3. ‘Waters’ usually ‘break’
• Expulsion


  1. Baby moves into a face-down position

  2. Contractions become stronger and closer together

  3. Forcing the baby through the birth canal
• The placental stage


  1. A final contraction expels the placenta

  2. Expels the umbilical cord

  3. Expels membranes (the after-birth)
• Fetal circulation is different to an adult circulatory system

  
• Fetal circulation components


  • Ductus Arteriosis
  • Ductus Venosus
  • Foramen ovale
  • Placenta
  • Umbilical cord

  
• Ductus Arteriosis


  Allows blood from the right ventricle to bypass the lungs by going straight to the aorta
• A small amount of blood still goes to the lungs to provide them with O2 and nutrients to develop
• Ductus Venosus


  Allows blood coming back from the placenta to bypass the liver and go straight to the inferior vena cava
• Ductus Venosus maximises the amount of O2 going back to the fetus

  
• Foramen ovale


  Allows blood from the right atrium to bypass the lungs by going straight to the left atrium
• Placenta


  Diffuses O2 and nutrients from the mother's circulatory system into the fetus' circulatory system

  
• Placenta allows CO2 and waste to diffuse from the fetus back to the mother
• Placenta produces oestrogen and progesterone
• Umbilical cord


  Contains two vessels
• Umbilical vein


  Carries O2 (oxygenated blood) and nutrients from the placenta back to the fetus

  
• Umbilical artery


  Carries CO2 (deoxygenated blood) and waste from the fetus back to the placenta