SEM-dissection of a human embryo derived from an ectopic pregnancy.

A 6.5-week-old human embryo with an approximate crown-rump length of 13.2 mm was obtained from a tubal pregnancy. Two hours before surgical removal, the embryo was imaged with real time ultrasound and was noted to have rhythmic cardiac motion. Subsequent to surgical removal, the embryo was dissected free from the placenta and prepared for routine scanning electron microscopic (SEM) studies. Progressive stages of dissection with microsurgical instruments followed by SEM photography elucidated the three-dimensional aspects of embryonic development of many structures, including the lens placode, tongue bud, Rathke's pouch, atrial and ventricular foramina, primitive intestinal loop and undifferentiated external genitalia. Almost certainly, such clear views of dissected structures can contribute to our understanding of human embryonic development.