Study Guide-Alterations in Hemostasis & Blood Coagulation

Vocabulary flashcards covering key terms and definitions from the lecture notes on hemostasis and blood coagulation.

Hemostasis

Process of stopping bleeding after vessel injury; balance between clot formation and prevention of excessive clotting.

Vasospasm

Immediate constriction of a damaged vessel to reduce blood flow.

Platelet plug formation

Platelets adhere to exposed collagen via vWF and GPIb, release ADP, TXA2, and serotonin to recruit more platelets, and GPIIb/IIIa binds fibrinogen for aggregation (~3–7 minutes).

Von Willebrand Factor (vWF)

Adhesive protein that binds platelets to exposed collagen via GPIb and carries factor VIII; defects cause mucosal bleeding, epistaxis, menorrhagia, and GI bleeding

GPIb receptor

Platelet surface receptor that binds vWF to promote platelet adhesion.

Platelets

Anucleate cell fragments; normal count 150,000–400,000/μL; lifespan 7–12 days; release clotting factors upon activation.

ADP (adenosine diphosphate)

Platelet secreted mediator that recruits/activates additional platelets.

Thromboxane A2 (TXA2)

Eicosanoid released by platelets promoting aggregation and vasoconstriction.

Fibrinogen (Factor I)

Soluble plasma protein converted by thrombin to fibrin; forms the clot scaffold and links platelets via GPIIb/IIIa.

Thrombin (IIa)

Enzyme that converts fibrinogen to fibrin; also activates platelets and factors V and VIII.

Factor XIII

Crosslinks and stabilizes the fibrin clot.

Coagulation cascade

Series of coagulation factors that produce a fibrin clot; comprises intrinsic, extrinsic, and common pathways.

Intrinsic pathway (aPTT)

Triggered by collagen/contact factors; activates to X; measured by aPTT.

Extrinsic pathway (PT)

Triggered by tissue factor (III) with VII to X; measured by PT.

Common pathway

Xa converts prothrombin (II) to thrombin and fibrinogen to fibrin; requires calcium and phospholipids.

Calcium

Essential cofactor at multiple steps in coagulation.

Fibrinogen (Factor I)

Soluble plasma protein converted to fibrin by thrombin to form the clot scaffold.

Prothrombin (Factor II)

Precursor to thrombin; when activated, it converts fibrinogen to fibrin.

Tissue factor (Factor III)

Initiates the extrinsic pathway in combination with Factor VII.

Factor VII

Part of the extrinsic pathway; activates X in the presence of tissue factor.

Factor VIII

Cofactor of the intrinsic pathway; deficiency causes Hemophilia A.

Factor IX

Cofactor of the intrinsic pathway; deficiency causes Hemophilia B.

Vitamin K-dependent factors

Factors II, VII, IX, X, and proteins C and S require vitamin K for synthesis.

Antithrombin III

Inhibits thrombin and other serine proteases; action enhanced by heparin.

Protein C and Protein S

Anticoagulant proteins that inactivate factors Va and VIIIa; require Protein S as a cofactor.

Bleeding time

Test of primary hemostasis; normal 3–10 minutes; prolonged with platelet dysfunction, vWD, or aspirin use.

PT (Prothrombin Time)

Test of extrinsic pathway; prolonged with vitamin K deficiency, liver disease, or warfarin.

aPTT (Activated Partial Thromboplastin Time)

Test of intrinsic pathway; prolonged with hemophilia, DIC, or heparin therapy.

INR (International Normalized Ratio)

Standardized PT value; normal ~1.0.

D-dimer

Fibrin degradation product; marker of clot breakdown elevated in DVT, PE, and DIC.

Disseminated Intravascular Coagulation (DIC)

Life-threatening condition of widespread clotting with consumption of clotting factors and bleeding; triggers include sepsis, trauma, obstetric complications; labs show low platelets and fibrinogen, prolonged PT/aPTT, high D-dimer.

Vitamin K deficiency

Affects factors II, VII, IX, X; newborn hemorrhagic disease; prolonged PT/INR (and sometimes aPTT); treated with vitamin K.

Hepatic disease

Liver is the primary site of clotting factor synthesis; cirrhosis or hepatitis reduces factor production and can cause a DIC-like state; treatment targets underlying disease, vitamin K, and plasma transfusion.

von Willebrand Disease (vWD)

Most common inherited bleeding disorder; defective/low vWF impairs platelet adhesion and lowers factor VIII; mucosal bleeding; treated with Desmopressin or vWF concentrates.

Desmopressin (DDAVP)

Drug that releases vWF (and factor VIII) from endothelial stores; used to treat vWD.

Vitamin K deficiency in newborns

Cause of hemorrhagic disease of the newborn; due to low vitamin K-dependent factor production.

Thrombocytopenia

Platelet count <150,000/μL; causes include production problems, destruction (e.g., ITP), and sequestration (splenomegaly).

Thrombocytosis

Platelet count >400,000/μL; can be essential or reactive; increases risk of thrombosis.

Vascular purpura

Petechiae or purpura from fragile vessels due to allergy, drugs, or vitamin C deficiency.

Hereditary Hemorrhagic Telangiectasia

Dilated capillaries/venules with recurrent epistaxis and GI bleeding.