Bleeding and Clotting Disorders[UNFINISHED]

Hemostasis

Cessation of bleeding

Primary Hemostasis

Platelet Aggregation

Secondary Hemostasis

Fibrin formation

Thrombus(clot)

Von Willebrand Factor

Attracts platelets

Platelet lifespan

7-10 days

Glycoprotein (GP) IIb/IIIa receptor

Present on platelet

Binds fibrinogen to enhance platelet aggregation

Blocked by anticoagulants

Thromboxane A2

Released by platelets

Promotes platelet aggregation

Site where platelets are sequestered

Spleen

Hemostasis 3 Major Steps

Vasoconstriction
Platelet Plug Formation

Blood Coagulation

What happens during platelet plug formation

Thrombopoietin synthesized by liver

Stimulates platelet formation

Thrombus(clot) Formation

‒ Response to injury

‒ Sluggish/stagnant blood flow

Thrombosis

Generation of an occlusive clot

Fibrinolysis

Clot dissolution

Coagulation reaction characteristics

Cascade reaction

Requires calcium and vitamin K

Has 2 pathways that both end in one common pathway

2 coagulation pathways

Intrinsic - damage to vessel

Extrinsic - damage to outside of vessel

Extrinsic pathway sequence

Factor VII+Tissue Factor=TF-factor VII

Factor X

Common pathway

Activation of factor VII

Caused by trauma

Comes into contact with tissue factor (TF) to form TF-factor VII

Extrinsic clotting time assessed by:

• Prothrombin time (PT)

• International normalized ratio (INR)

Intrinsic Pathway Sequence

Factor XII

Factor XI

Factor IX + Factor VIII=Intrinsic Tenase Complex

Factor X

Activation of factor XII

• Injury to vessel

• Stasis of blood

Intrinsic clotting time assessed by

Activated partial thromboplastin time (aPTT)

fibrinolysis step 1

Tissue plasminogen activator (tPA) release

fibrinolysis step 2

tPA converts plasminogen(from liver) to plasmin

fibrinolysis step 3

Plasmin breaks down clots

rtPA

Recombinant tissue plasminogen activator(alteplase)

Therapeutic use to break down clots

Clotting problems causes

Excessive platelet numbers

Enhanced coagulation activity

Clotting causes examples

• Splenectomy

• Myeloproliferative disorder

Paradoxical bleeding

Elevated platelets are dysfunctional

Bleeding problems causes

Inadequate platelet numbers

Missing coagulation factors

Decreased coagulation activity