Embryonic development and placenta
Fertilisation and pregnancy · Biology
Study notes
By week 8, the embryo — now called a foetus — has all organs formed, fingers, toes, and a beating heart visible on ultrasound. Smoking or alcohol in pregnancy crosses the placenta: foetal alcohol syndrome causes lifelong learning disabilities — the placenta feeds but doesn't filter everything. The umbilical cord's two arteries and one vein are the baby's entire supply line for 9 months.