The Clot Thickens

If you cut yourself a clot soon forms to stop you from bleeding, like the one shown here under a high-powered microscope. Special cells in the blood spring into action to create a thick mesh of protein fibres, sealing the wound and fighting any infection that might try to get in. But while clots usually stop our blood from leaking out and nasty things getting in, they're dangerous if they accidentally form on the inside of blood vessels. This shouldn't normally happen, but certain diseases and conditions such as diabetes or obesity can increase the risk. If part of the clot breaks off and starts travelling around the body, it can block crucial blood vessels causing a heart attack, stroke or other serious problems.

• Image by Fraser Macrae
• University of Leeds
• Copyright held by original author
• Winner of the British Heart Foundation's Reflections of Research Image Competition 2014