If you cut yourself and begin to bleed, the damaged tissues immediately release a chemical that initiates a chain reaction. Tiny disk-shaped platelets in your blood build up to form a plug at the injury site, and proteins in the blood plasma reinforce the clot by forming fibrous strands at the site. If a sample of blood is carefully removed from the blood vessel without allowing it to come in contact with the damaged tissue, and then the sample is placed on a smooth, plastic plate exposed to air, the blood will not clot. However, if a rough plastic plate or a glass plate is used instead, the blood will clot. What helps cause blood to clot?
a response from damaged blood tissue
The chemical response from the damaged tissue initiates the chain of responses that result in a blot clot that minimizes blood loss.