At 24 weeks, magnetic resonance imaging shows just a few nascent grooves in the otherwise smooth surface of the fetal brain, according to a 2000 study in the journal Radiology.
These fetal kidneys (from a gestation estimated at 25 weeks in the second trimester) demonstrate a normal cut surface. Note the pelvis and calyces. Note the well-defined corticomedullary junctions.
这是妊娠中期，估计为25周胎儿肾。切面正常，可见肾盂、肾盏，皮质、髓质分界清楚。
3
Except the ordinary fetal membranes, full-term fetus had another membrane close to the surface of the body which was derived from the surface of the skin.