Medical Research Council - London Institute of Medical Sciences

Now in our 9th year of bringing you beautiful imagery from biomedical science every day

25 December 2017

Platelets Pull Together

When a blood vessel is injured, platelets (green) – tiny blood cells without nuclei – are the first on the scene, sticking to the vessel walls surrounding the injury site and assembling a meshwork of fibrin molecules (red) between them. This platelet and fibrin bundle (or clot) then contracts, as shown in the video, which serves two purposes: closing the wound to prevent blood loss, and preventing the vessel itself from becoming blocked by the clot. Although scientists were aware of the major molecular players controlling this remarkable feat of compression, the precise mechanism at work was a mystery. Now state-of-the-art microscopy has uncovered the dynamics of clot contraction, revealing that platelets extend thin, arm-like projections, called filopodia (visible in the video), that grab and pull on the fibrin cables and draw the cells together.

Written by Ruth Williams

Search The Archive

Submit An Image

What is BPoD?

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.

Read More

BPoD is also available in Catalan at with translations by the University of Valencia.