Why do platelets initially stick to the wall of a damaged blood vessel?

Question

Why do platelets initially stick to the wall of a damaged blood vessel?

Answer 1

When a blood vessel ruptures, the ruptured platelets and the damaged wall of the blood vessel release thromboplastin. Thromboplastin is an enzyme that changes prothrombin into thrombin, an enzyme which converts the soluble fibrinogen into insoluble strands of fibrin. A network of fibrin strands traps platelets, causing them to stick to the wall of the damaged blood vessel and form a clot.

Answer 2

When a blood vessel is damaged, a cascading effect occurs, what happens is the damaged tissue protein signal changes, and the change in the signal causes the platelets to aggregate around the damaged tissue.  It's a very complicated mechanism.

Answer 3

MD hematologist answer

"cdubU" is basically right.  

In simpler terms, think about what happens when you cut yourself.  There are small broken blood vessels that bleed, but the bleeding stops quickly with a little pressure.  The platelets are the small blood cells that are supposed to adhere to torn, ragged blood vessels and initiate the coagulation cascade and stop bleeding.  

Platelets are "dumb animals."  By that I mean they do not know when a ragged blood vessel is injured by trauma or just presents a rough surface due to cholesterol deposits / plaques.  Platelet adhesion can be blocked by drugs such as aspirin which inhibit platelet aggregation.  That is fine for preventing heart attacks and strokes, but it means there will be more bleeding with trauma.  

Medicines usually have good and bad sides.  People who expect perfect performance from drugs with no risk of side effects are not understanding the real world.