A deep cut to the skin may need stitches to keep two sides of a wound in place while they knit together. Inside developing embryos, where tissues 'zip up' over organs for the very first time, it's mechanical forces that pull cells together. In this fly embryo, pictured under a confocal microscope, rainbow-coloured fluorescence highlights actin, a structural protein inside fly cells (and our own) which bends and flexes to create tension. The embryo puts this force to good use in closing the skin over its back – a process called dorsal closure, which is similar to human wound healing. Cells in the amnioserosa (the eye-shaped gap in the centre) contract and pull against each other, changing their size and shape to close the hole. Watching the intricate steps in the process may reveal a thing or two about human tissues, too.
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.