Introduction to Hemostasis I Flashcards
At sites of injury, vasoconstriction is induced by __________.
factors released by endothelial cells
List the cofactors of the intrinsic pathway.
HMWK, VIII, and V
List the cofactors of the extrinsic pathway.
TF and V
Most of the proteases in the coagulation cascade are _______.
serine proteases that exist in the blood as zymogens; they cleave targets at arginine residues
The serine-protease pattern holds true except for _______.
factor VIII, which is a transglutaminase (forms a lysine-glutamine bond)
What does factor XIIIa do?
It cross links the polymerized fibrin molecules.
All of the blood factors are made in the liver, with the exceptions of _________.
von Willebrand factor (found on endothelial cells and platelets), factor VIII (produced by many different organs), and tissue factor (found on the surface of cells)
Those with liver disease often have poor _______ absorption, due to _______.
vitamin K; deficient fat absorption
Vitamin K (so named for its association with coagulation, because Germans spell coagulation with a K) is necessary for ________.
post-translational modification of coagulation factors
Surface contact can initiate the _______ pathway.
intrinsic
HMWK is _________.
high molecular weight kininogen
The vitamin K-dependent serine proteases are __________.
II, VII, IX, X, and protein C
Warfarin is the ________ name, while Coumadin is the ______ name.
generic; brand
The only enzyme in the clotting cascade that is not a serine protease is _________.
factor XIII, which is a transglutaminase
Cofactors in the clotting cascade are _______.
tissue factor, VIII, V, and HMWK
Tissue factor is not normally expressed on __________, but is on ________.
cells in contact with the blood (unless they are under stress or exposed to LPS); fibroblasts and smooth muscle cells
Structurally, fibrinogen is composed of _______.
an E unit surrounded by two D units (on either side)
vWF is produced and stored in ________; it carries ________.
granules in platelets and endothelial cells; factor VIII
Extrinsic tenase is ________.
factor VIIa, tissue factor, and factor X
Intrinsic tenase is _________.
factors IXa, VIIIa, and X
What three reactions occur on a negatively charged phospholipid in the presence of calcium?
The intrinsic tenase reaction, extrinsic tenase reaction, and the prothrombinase reaction
Once prothrombin has been activated to thrombin, thrombin also ___________.
activates V, VIII, XI, and platelets–which amplifies the pathway–and activates XIII
XIa activates _________.
more IX
There is always some amount of circulating ______, but it does not initiate clotting because ________.
VIIa; it requires tissue factor to become active, which will only be exposed in injured endothelium
Factor V is activated by _________.
factors Xa and IIa; Xa then uses factor Va to activate factor II
The intrinsic tenase pathway is ________ than the extrinsic pathway.
50 - 100 times faster
Prothrombin time tests __________.
the extrinsic pathway
APTT is ____________.
the activated partial thromboplastin time; it tests the intrinsic pathway
What three things does TF+VIIa activate?
X, IX, and VII
IIa amplifies the cascade by _________.
activating more VIIIa, XIa, and Va
XIIIa is activated by _________.
factor IIa
