During the menstrual cycle, there is a window of two to four days when the uterus is receptive to embryo implantation. Cells in the lining of the uterus must then switch from receptive to protective to shelter the developing embryo from stress. This picture shows cells that line the human uterus secreting an enzyme called SGK1 (stained in green; red and blues dyes mark other cell compartments). If SGK1 is not produced a miscarriage could ensue. But producing too much SGK1 too soon, can cause problems with embryo implantation. The relationship between SGK1 and survival of the embryo makes it a crucial switch for the body to get right when early life hangs in the balance.
Written by John Ankers
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.