Many of the tissues in our body are constantly renewing, but none so fast as the lining of our gut. Each epithelial cell lining the human intestine lasts about a week. They start life in deep pits called crypts and, as they age, are pushed further up the steep sides of tiny projections called villi, which protrude into the intestinal space. At the tips of the villi, the cells die and detach. Scientists can now examine the lives of gut cells in more detail thanks to a clever labeling trick whereby stem cells in the crypts randomly switch on one of four fluorescent proteins (red, yellow, green or blue). Pictured is a crypt showing epithelial descendants each bearing the colour of its stem cell, making it easy to trace the origins of these short-lived cells.
Written by Ruth Williams
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) 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.