A new shape of the red blood cell helps to seal the clot. The erythrocyte (red blood cell, on the left) loses its typical biconcave shape when it is incorporated into the clot. In particular, at the center of the blood clot, due to the pressures induced by clot contraction (platelets pulling at fibrin fibers), the red blood cell takes up a different, new shape of a polyhedrocyte (right). The polyhedrocyte is characterized by flat surfaces and straight edges, which, when packed closely together, makes an almost perfect seal at the center of the blood clot, reducing blood loss.1 Professional illustration by Alice Y. Chen.
