Which tiny blood cells help wounds to clot and stop bleeding?

Platelets are tiny blood components that help wounds clot and stop bleeding. Also called thrombocytes, they rush to damaged blood vessels, attach to the exposed area, change shape, and release chemical signals that attract and activate additional platelets. Together they form a temporary platelet plug, the first major stage of haemostasis.

Platelets are not complete cells in the usual sense. In mammals, they are small, nucleus-free fragments shed by very large bone-marrow cells called megakaryocytes. Once activated, platelets connect through receptor bridges and create a surface where the coagulation cascade can operate. Fibrin strands then reinforce the plug and help form a stronger clot.

A common mix-up is confusing platelets with red or white blood cells. Red blood cells carry oxygen, while white blood cells help defend against infection. Plasma is the liquid portion of blood and carries cells, proteins, nutrients, and hormones, but it is not itself a blood cell. Platelets also release growth factors and other signals that can support tissue repair after an injury.