Answer
18.2:2
Extra-embryonic membranes include amnion, allantois, chorion, and yolk sac.
1. Amnion: The amnion contains fluid that bathes the embryo, cushions and protects it.
2. Allantois: This membrane gives rise to the urinary bladder; itc ollects embryogenic urine (the nitrogenous
waste) produced by the kidneys .
3. The yolk sac: Many blood vessels develop from the yolk sac; it is the first site of blood cell formation.
Work Step by Step
4. The chorion forms the fetal half of the placenta; chorionic villi increase the absorptive area of this membrane, and chorionic blood vessels connect with umbilical blood vessels
