A 32-year-old pregnant woman presents to the obstetrics clinic for a routine prenatal check-up at 20 weeks gestation. During the ultrasound examination, the obstetrician notes the presence of a well-defined amniotic cavity surrounding the fetus. The amniotic fluid appears to be within normal limits. 

Which of the following embryonic layers is responsible for the formation of the lining membrane of the amniotic cavity?