The Hemostasis Trilogy (Steps 1–3)
This fast, localized response constricts a damaged vessel to limit blood flow.
What is vascular spasm?
Both intrinsic and extrinsic pathways lead to activation of this clotting factor.
What is Factor X?
During clot retraction, platelets contract using these proteins.
What are actin and myosin
A clot that forms in an unbroken vessel is called this.
What is a thrombus
Type O blood can be given to most recipients because it lacks these RBC markers.
What are A and B antigens
Pain reflexes, endothelial chemicals, and smooth muscle injury all trigger this step.
What is vasoconstriction during vascular spasm?
The intrinsic pathway is triggered by surfaces with this charge.
What is a negative charge (collagen, activated platelet phospholipids, glass)
The inactive form of the fibrin-digesting enzyme is called this.
What is plasminogen
A thrombus that breaks free and travels in the bloodstream becomes this.
What is an embolus
People with type AB blood are universal recipients because they lack these.
What are anti-A and anti-B antibodies
Platelet activation releases these three substances that intensify aggregation.
What are ADP, serotonin, and thromboxane A₂
The extrinsic pathway is initiated by release of this substance from damaged tissues.
What is Tissue Factor (Factor III)?
This enzyme converts plasminogen into plasmin.
What is tPA (tissue plasminogen activator)?
Platelet count <150,000/µL leads to this condition, often causing petechiae.
What is thrombocytopenia
Anti-Rh antibodies do NOT form spontaneously; they form only after this event.
What is exposure to Rh+ blood?
This protein unfolds and helps platelets adhere to exposed collagen.
What is von Willebrand factor (VWF)
Thrombin converts this soluble protein into insoluble fibrin.
What is fibrinogen
This molecule inactivates thrombin that escapes the clot.
What is antithrombin III?
Hemophilia A results from deficiency of this clotting factor.
What is Factor VIII
This condition occurs when an Rh– mother carries an Rh+ fetus in a second pregnancy.
What is erythroblastosis fetalis?
Coagulation reinforces the platelet plug with these structural protein strands.
What are fibrin threads
To stabilize the clot, thrombin and Ca²⁺ activate this factor which cross-links fibrin.
What is Factor XIII (fibrin stabilizing factor)?
These two endothelial substances prevent platelet adhesion under normal conditions.
What are nitric oxide (NO) and prostacyclin?
Vitamin K deficiency or cirrhosis can impair clotting because the liver cannot produce these.
What are procoagulants (clotting factors)?
During a transfusion reaction, donor RBCs clump because the recipient’s plasma contains these.
What are agglutinins (antibodies)?