File:Mouse- early conceptus.jpg

Asymmetries between fetus and rest of conceptus and shape of regular tetrahedral 4-cell stage.

A). Diagram of a rotated fetus in situ with the parietal yolk sac (PYS) reflected back to the base of the chorio-allantoic placenta (CAP). The right side of the fetus faces towards the placenta, as does the umbilical cord (UC). Its tail (FT) is curled back against the right side of the trunk and head (FH), while the vitelline artery and vein (VAV) connect to the visceral yolk sac (VYS) from the left side of the still open abdomen.

B) Diagram of a regular tetrahedral 4-cell stage conceptus showing the disposition of the products of meridional (A/B blastomeres) versus equatorial (C and D blastomeres) second cleavage relative to the second polar body (pb).

Pone.0009610.g001.jpg

Normal Bias in the Direction of Fetal Rotation Depends on Blastomere Composition during Early Cleavage in the Mouse Richard L. Gardner PLoS One. 2010; 5(3): e9610. Published online 2010 March 10. doi: 10.1371/journal.pone.0009610. PMCID: PMC2835742 | PLoS

PLoS One. 2010; 5(3): e9610. Published online 2010 March 10. doi: 10.1371/journal.pone.0009610.

Copyright Richard L. Gardner. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.