Hemostasis Flashcards
Hemostasis
the process of stopping blood from leaving an injured blood vessel
3 major steps of hemostasis
vasoconstriction, development of a platelet plug, blood coagulation
Why is hemostasis a protective mechanism
forms a thrombus to prevent the excessive blood loss from the body
Step 1 vasoconstriction
temporarily decreases blood flow and pressure within the vessel caused by vasoconstrictive paracrine released by the endothelium
Stage 2 platelet plug development
a thrombus is formed when platelets aggregate and are reinforced by fibrin in response body injury, blood vessel wall damage, sluggish/stagnant blood flow
Stage 3 blood coagulation
coagulation cascade that ends with the development of fibrin strands that strengthen the platelet plug
What does the cascade end with
the development of fibrin strands that strengthen the platelet plug
Thrombocytopenia
low platelet count, <100,000, can cause bleeding
Thrombocytosis
high platelet count, >750,000, can cause excessive clotting
What occurs during primary hemostasis
platelets form a platelet plug
What occurs during secondary hemostasis
coagulation cascade
What is platelet formation stimulated by
thrombopoietin (synthesized in the liver)
What is the normal platelet lifespan
7-10 days
How many platelets does a healthy spleen contain
1/3 of total platelets
Characteristics of an unhealthy spleen
enlarged and hyperactive, containing 80% of the body’s platelets
