Flashcards in CH4 - Hemostasis and Related Disorders Deck (213)
What is hemostatsis?
Damage to the wall is repaired by hemostasis,
Hemostasis involves the formation of?
a thrombus (clot) at the site of vessel injury
primary and secondary.
forms a weak platelet plug
Primary hemostasis is mediated by?
interaction between platelets and the vessel wall
stabilizes the platelet plug
Secondary hemostasis is mediated by?
the coagulation cascade.
What is Step 1 in secondary hemostasis?
Transient vasoconstriction of damaged vessel
How is Step 1 in secondary hemostasis mediated?
by reflex neural stimulation and endothelin release from endothelial cells
What is Step 2 in secondary hemostasis?
Platelet adhesion to the surface of disrupted vessel
In step 2 of secondary hemostasis, how does platelet adhesion occur?
Von Willebrand factor (vWF) binds exposed subendothelial collagen,
How do platelets bind to vWF?
via the GPIb receptor
vWF is derived from?
the Weibel-Palade bodies of endothelial cells and a-granules of platelets.
What is Step 3 in secondary hemostasis?
In step 3 of secondary hemostasis what does Adhesion induce?
shape change in platelets and degranulation with release of multiple mediators
What are the mediators released in step 3 of secondary hemostasis?
ADP and TXA
What is the role of ADP in step 3 of secondary hemostasis?
it is released from platelet dense granules; promotes exposure of GPIIb/IIIa receptor on platelets.
What is the role of TXA in step 3 of secondary hemostasis?
it is synthesized by platelet cyclooxygenase (COX) and released; promotes platelet aggregation
What is step 4 in secondary hemostasis?
Step 4?Platelet aggregation
Where and how do Platelets aggregate in step 4 of secondary hemostasis?
at the site of injury via GPIIb/IIIa using fibrinogen (from plasma) as a linking molecule;
What does platelet aggregation result in?
formation of platelet plug
It is weak; coagulation cascade (secondary hemostasis) stabilizes it.
What are disorders of primary hemostasis usually due to?
Usually due to abnormalities in platelets;
Disorders of primary hemostasis are divided into?
quantitative or qualitative disorders
What are some Clinical features for disorders of primary hemostasis?
mucosal and skin bleeding.
What is the most common overall symptom in mucosal bleeding?
What are symptoms of mucosal bleeding?
epistaxis, hemoptysis, GI bleeding, hematuria, and menorrhagia. Intracranial bleeding occurs with severe thrombocytopenia.
What are the symptoms of skin bleeding?
include petechiae (1-2 mm), ecchymoses (> 3 mm), purpura (> 1 cm), and easy bruising;
Petechiae are a sign of what?
thrombocytopenia and are not usually seen with qualitative disorders.