LM of a polarized stage 1b embryo in vitro with pronuclear alignment along the polar axis (interrupted line). The second polar body indicates the first cleavage plane and marks the polar axis until the blastocyst stage (stage 3). Pronuclei rotate into the polar axis.
From: Veeck and Zaninovic´, 2003. Reproduced with permission of the publisher, Taylor & Francis Group.
Keywords: first cleavage plane, polar axis, pronuclear alignment, pronucleus, second polar body
Source: The Virtual Human Embryo.