chapter 5 - embryology

• Umbilical vessels

  • Umbilical arteries
  • Umbilical veins
• Umbilical arteries

  Carry deoxygenated blood from fetus to placenta
• Umbilical veins

  Carry oxygenated blood from placenta to fetus
• Human pregnancy lasts about 266 days
• Gestation is divided into 3 trimesters
• First trimester

  • Major organs start developing
  • Heart starts beating at 22 days
  • By end of 8 weeks, most organs are formed, and embryo is called fetus
  • Fetus is 9 cm by end of 3rd month
• Second trimester

  • Fetus grows a lot
  • Starts moving in the amniotic fluid
  • Face, fingers, toes become more defined
  • By end of 6th month, fetus is about 30-36 cm long
• Third trimester

  • Rapid growth and brain development
  • In 9th month, fetus receives antibodies from mother for protection
  • Growth rate slows, and fetus becomes less active due to limited space