A layer of tightly packed cells called the endothelium lines our blood vessels. These cells constantly communicate with the blood cells rushing past. When we exercise they release chemical signals to increase blood pressure, so that more blood reaches our muscles. In the event of an injury they send out alarms, which constrict vessels to reduce bleeding, activate wound plugging and alert our immune system to invading bacteria. Endothelial cells can also change shape – here, we see their outlines stained green and centres, or nuclei, dyed blue. Stretching into long, oval shapes in line with the blood flow may help them converse more effectively. Scientists are studying the habits of these versatile cells to understand how they can become damaged, which can lead to blood clots, blocked arteries, haemorrhages, heart attacks and strokes.
Written by Mick Warwicker
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