The embryonic period of a time of rapid organogenesis. By about what age are all organ systems recognizable?

In the fetus, the ductus arteriosus carries blood from

(a) the pulmonary artery to the pulmonary vein

(b) the liver to the inferior vena cava

(c) the right ventricle to the left ventricle

(d) the pulmonary trunk to the aorta

Jenna, a freshman in your dormitory, tells you she just discovered that she is three months pregnant. She recently bragged that since she came to college she has been drinking alcohol heavily and experimenting with every kind of recreational drug she could find. From the following, select the advice you would give her, and explain why it is the best choice.

(a) She must stop taking drugs, but they could not have affected her fetus during these first few months of her pregnancy.

(b) Harmful substances usually cannot pass from mother to embryo, so she can keep using drugs.

(c) There could be defects in the fetus, so she should stop using drugs and visit a doctor as soon as possible.

(d) If she has not taken any drugs in the last week, she is okay.

Which of the following is the middle layer of the trilaminar disc?

Which of the following structures helps to organize the embryo around a central axis?

Which of the following structures is NOT formed by neural crest cells?