Hemostasis Flashcards
Endothelium
Controls blood flow rate and vessel permeability
Negatively charged
secretes procoagulant and anticoagulants
Hemostasis
Balance between bleeding and thrombosis
Initiated by a break in the endothelial membrane
Procoagulant
Von Willibrand factor
tissue factor
thrombomodulin
Primary hemostasis
first response to injury
local vasoconstriction
limit bleeding
lasts for a few minutes only
Platelets
Inactive cellular element stimulated by the endothelium
Adheres to break in endothelium
flattens at the site of injury and develops receptors for clotting factors
aggregates with other platelets (unstable clot)
Platelet adhesion
Interaction with platelet and endothelium
Von Willibrand factor
Von Willibrand factor most common in platelet adhesion
Platelet activation
Alpha granules form stable connection with other platelets
Platelet plug
Still an unstable hemostatic plug
Coagulation Cascade / Secondary Hemostasis
fibrin clot formation; cements the clot together
Calcium
crucial component of secondary hemostasis
Clotting factors
factor 1: etc etc
Protein C and Protein S
clot formation inhibitor. W/o this you will form clots that result to infarctions
Intrinsic pathway
Fibrinolysis
requires activation of plasmin
Thrombus
clot in an unbroken vessel
Embolus
abnormal object moving through a blood vessel, clot, air bubble, lipid droplet, thrombus, etc.
Heparin
Anticoagulant against thrombin
Thomboembolism
Common causes: (Thrombi) Tissue damage Hereditary Rest Obstetric Malignancy Blood Flow Immune mechanisms
Ecchymoses
bruise not caused by trauma (hematoma)
Coagulation disorders
hematomas are deep
bleeding into cavities
delayed bleeding (bleeding and bleeding)
pressure may not control bleeding
Petechiae
small pinpoint hematomas (red dots)
superficial
caused by minor hemorrhage
dysfunctional platelets
Purpuras
round in diameter, about 1 cm, bruise
purple discoloration of skins
bleeding under skin
Hematoma
collection of clotted blood in an organ, tissue, space or cavity
hemarthrosis
bleeding into joints, a hematoma
Prothrombin time
measures extrinsic pathway, a test
apTT
measures intrinsic pathway, a test
prolongs only if factor levels are low
Vitamin K
inhibitor of coagulation
factors 2, 7, 9, 10 -> extrinsic pathway, Vitamin K dependent factors
post translational modification of these factors (activates them) requires vitamin K
Thrombin time
time to form a clot, a test
prolongation is due to decreased fibrinogen activity
Coagulation-factor assay
Deficiencies:
factor 8: hemophilia A
factor 9: hemophilia B
factor 11: hemophilia C
Hemophilia usually presents as significant bleeding
factor 12 not associated with clinical bleeding
Vascular defects
no platelet or coagulation problem spontaneous bleeds lab findings may be normal fragile blood vessels ex. scurvy, senile purpura, etc
Von Willebrand factor deficiency
most common congenital bleeding disorder
usually in females
Warfarin
antagonist of vitamin K
