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The Amazing Red Blood Cell

We have always been taught that red blood cells are shaped like bi-concave discs to maximize oxygen exchange in the capillaries. However, Francis Collins recently reported on his NIH Directors Blog that red blood cells change into angular polyhedrocytes they become entangled within the platelet-fibrin network of an evolving blood clot. Fibrin contraction causes platelets and fibrin to be pushed towards the outer edges of the thrombus and red cells to be compacted within in the center. Under this pressure, red blood cells take on an angular shape. This shape change eliminates gaps between cells, creating an impermeable clot.

This new discovery may explain why tissue plasminogen activator is most effective in reestablishing circulation when it is administered as soon as possible after after the onset of a stroke or myocardial infarction. TPA has a better chance of penetrating the gaps between cells before red blood cells undergo their shape change.


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