CPM Certified Professional Midwife

Answer: A - Connective stalk

The connective stalk is a yolk sac diverticulum. The umbilical cord is created when the connective stalk and the ductus omphalo - entericus (along with umbilical coelom) are enveloped by the spreading amnion. This occurs approximately between the fourth to eighth week of pregnancy. The umbilical cord connects the fetus to the placenta, and permits fetal circulation of blood. Idevelops from the connective stalk (or body stalk) which is a band of mesoblastic tissue.