Hemostasis Flashcards
Coagulation
What is hemostasis?
The process by which the body control bleeding and maintains blood in a fluid form.
Hemostasis is composed of? (4)
- Vascular system (blood vessels)
- Platelets
- Coagulation (factors)
- Fibrinolysis
What activates the primary hemostasis system? What 2 functions are primarily involved?
- Activated by small vessel damage.
- Vasoconstriction
- Platelet function
What activates the secondary hemostasis system? What 2 functions are mainly involved?
- Activated by major trauma, surgery, or hemorrhage
- Coagulation proteins
- Enzymatic reactions
What is vasoconstriction?
ability of small vessels to contract which decreases the diameter of of blood vessels and decrease blood flow.
What do platelets do?
Form a platelet plug
Coagulation is is dependent on a series of _______ that take part in a series of ______ ______ resulting in the formation of ______.
Proteins enzymatic reactions Fibrin
The secondary system also includes _______ which is clot _____ once the blood loss has stopped and the vessel repaired.
Fibrinolysis dissolution
The vascular system prevents bleeding through? (3)
- Vessel constriction
- Activation of PLTs
- Activation of coagulation system
The vessel wall contains Fibrous tissue consisting of? (3)
- Collagen
- elastic fibers
- smooth muscle
An injured vessel exposes collagen which reacts with PLTs via what factor?
von Willebrand factor
What is the life span of a PLT?
7 - 10 days
What stimulates PLT production?
Thrombopoietin
PLT parent cell is the _______ that undergoes ________.
Megakaryocyte Endomitosis
There are no significant # of PLTs in bone marrow, _____ in circulation, and _____ in spleen.
67% Circulation 33% Spleen
What are the 3 phases of PLT function?
Adhesion Amplification Aggregation
What happens during PLT adhesion?
What factor and PLT receptor is required? (2)
What is secreted?
- PLTs adhere to collagen and change shape (when they interact)
- Required: von Willebrand factor (vWF) and Glycoprotein 1b (GpIb)
- Secretion of PLT and clot activating substances.
What happens during Amplification?
What helps this?
- Secreted substances recruit more PLTs to aggregate.
- Thromboxane A2
What happens during Aggregation?
What receptors do PLTs use to adhere?
PLTs adhere to other PLTs
Uses GpIIb and GpIIIa to adhere with oth. PLTs via plasma proteins such as fibrinogen.
T/F: PLTs play and important roles in the formation of the primary PLT plug (primary hemostasis) as well and the coagulation cascade (secondary hemostasis)
True
PLTs serve as the site for?
Coagulation
What are coagulation factors?
Blood proteins that conclude with an insoluble fibrin clot
Where are all coagulation factors produced? Which one is not produced here?
Liver EXCEPT factor VIII
What are the two different pathways for clotting?
- Extrinsic (Tissue factor pathway): Rapid response to tissue injury.
- Intrinsic (Contact activation pathway): slower response, but quantitatively more significant.
- Factor I (Fibrinogen) is a substrate for?
- and a precursor for?
- Is the largest?
- What 2 forms is it converted to?
- Polymerized clot forms when exposed to _____.
- Thrombin
- Fibrin
- Largest molecular weight
- Insoluble (fibrin that forms clot) Soluble (soluble peptides cleaved from fibrinogen to make fibrin)
- Thrombin
What is Factor II (prothrombin) converted to?
What does its converted form do?
Converted to Thrombin IIa (activated), which cleaves fibrinogen
What does Factor II (prothrombin) activate? (3)
- Cofactors,
- protein C,
- and Factor XIII
Factor III (thromboplastin) activates this factor when blood is exposed to ____ ____.
Factor VII, tissue fluids
What is Factor IV (ionized (active) calcium) needed for? (2)
- Activation of thromboplastin (factor III)
- Conversion of prothrobin to thrombin
Factor V (proaccelerin or labile factor) speeds up which process?
prothrobrin to thrombin.
What factor is consumed during clotting?
V
20% of what factors are found on platelets?
V
Which factor is nonexisitent?
VI
What factor is activated by tissue thromboplastin (factor III) and activates Factor X?
Factor VII (proconvectin or stable factor)
What factor is needed for the cleavage of Factor X to Xa by IX?
Factor VIII (antihemophilic factor)
What factor is deficient in hemophilia A?
Factor VIII (antihemophilic factor)
What factor is a plasma thromboplastin (factor III) component?
Factor IX
What factor is deficient in hemophilia B
Factor IX
What factor known as Stuart-Prower merges to form conversion of prothrombin to thrombin
Factor X
What factor is independently activated by Russell’s Viper Venom.
Factor X
What factor is essential to the intrinsic pathway, with a decreased frequency in the Jewish population, and bleeding tendencies vary?
Factor XI, a plasma thromboplastin antecedent
Known as Hageman factor, it is an activated contact factor that is activated by collagen. A deficiency may cause a prolonged PTT but not a bleeding problem, with a tendency toward thrombosis.
Factor XII
This is a firbrin stabilizing factor, stabilizes polymerized fibrin monomers in the initial clot when exposed to calcium.
Factor XIII
What are the 3 receptors on PLTs?
GpIb, GpIIb, and GpIIIa
This the surface contact factor activated by kallikrein.
High-molecular weight kininogen (HMWK) *Homework
Known as Fletcher factor, this is a surface contact activator.
Pre-kallikrein
Identify the process involved in the coagulation cascade from activation to stable clot formation? (4)
- Vessel injury activates common pathway
- results/leads to formation of fibrin clot
- factor XIII stabilizes fibrin clot
- Thrombin feedback activation of V, VIII, and XI amplify process.
What are Regulatory Inhibitors?
Soluble proteins that are natural anticoagulants
Protease inhibitors (3)
- Antithrombin
- Protein C / Protein S
- Tissue Factor Pathway Inhibitor (TFPI)
What is the Fibrinolytic System?
System that dissolves blood clots
Plasminogen is converted to plasmin which does what in the fibrinolytic process?
breaks down fibrin clot into fibrin products
What are the characteristics of inhibitors (3)
- Block activated coagulation factors, so widespread coag not occur.
- Limit fibrinolysis and neutralize activated factors in circulation.
- Each has a specific role.
PT measures which pathway?
- Extrinsic pathway
aPTT (activated Partial Thromboplastin Time) measures which pathway?
Intrinsic Pathway
Abnormal PT/Normal PTT
Factor VII defieciency (Extrinsic)
Abnormal PTT/ Normal PT
Defieciency of Factors:
- XII
- XI
- IX
- VIII
Abnormal PTT and PT
Deficiency of Factors:
- X
- V
- II
- I
What is in the Contact group?
- PreKal
- HMWK
- XI
- XII
These factors are in the Prothrobin Group, and are Vitamin K dependent?
- 1972
- X
- IX
- VII
- II
What factor is common to all 3 pathways?
X
What medications are used w/ abnormal PT?
What medications are used w/ abnormal aPTT?
- Warfarin
- Coumadin
- Heparin
