Blood Platelets (Thrombocytes)

Tiny discs swim in your blood — barely visible, less than a thousandth of a millimeter thick. They are called thrombocytes, known in everyday language as blood platelets. When you cut yourself, they are the first to react. Within seconds they rush to the injured site, become sticky, cling to each other, seal the leak. They are the body's quiet repair crew — the hand that immediately presses shut every wound.

If there are too few, the smallest injury keeps bleeding. A bruise appears from nowhere. Gums begin to seep while brushing teeth. A scrape becomes a story that will not end. If there are too many, or if they become active too quickly, the blood clots where it should be flowing. A clump blocks a vein, a clot travels to the lungs or brain. What was meant to protect becomes a danger.