By 17 to 22 mm, we are measuring a recognizable crown-rump length (CRL) (Figure 10). Before 17 mm,
the measurements
of ES are
the greatest measurement along
the long axis
of the embryo. By 10 weeks LMP, the further unfolding of the head, final regression of the tail, regression of the heart prominence, and development of the limbs and eyes allow this primitive tadpole-like form to now be recognizable as human in form-hence, fetus (from the Latin word for "offspring").