1. HEMOSTASIS – Stoppage of Blood Flow.
3 Steps;
A. Platelet Plug Formation
B. Vascular Spasm.
C. Coagulation

2. Platelet Plug Formation
Begins with a break in blood vessel lining. (endothelium)
Break in vessel wall exposes collagen fibers.
Platelets are attracted to fibers and stick to it.
Platelets release chemical signals that attract more platelets to the bleeding vessel.
Piled up platelets are referred to as a “platelet plug” or “white thrombus.”

4. Platelets accumulating to form platelet plug.

5. Vascular Spasm Anchored platelets release serotonin.
Causes blood vessel to “spasm”
Motion narrows / constricts injured vessel.
Blood flow is reduced until clot can completely form.

6. Image of Vascular Spasm in Coronary Artery.
Normal Blood Vessel.
Constricted Blood Vessel

7. Coagulation Injured vessel releases Thromboplastin.
PF3 on platelets reacts with thromboplastin to form Prothrombin Activator and begin “Clotting Cascade.”
Prothrombin Activator converts Prothrombin to Thrombin. (Prothrombin is located in plasma.
Thrombin joins Fibrinogen fibers into long strands called Fibrin.
RBC’s get trapped in the fibrin mesh and form the clot.

8. Red Blood Cells Trapped in Fibrin Mesh

9. Entire process takes 3 – 6 minutes to complete.
After 1 hour, clot begins to go away.
Vessel begins to heal by pulling edges closed and making new endothelium.

10. THE END!!