hemostasis/coag. Flashcards
Define hemostasis
cessation of bleeding from cut or severed vessel
what are platelets produced from
megakaryocytes
platelet survival time
8-10 days
where doe plat. membrane come from
off megakaryocyte
what is contained on plat. membranes
- procoag. PS
2. surface receptors
2 main platelet integrins and ligands
- GP2b-3a - VWF and fibrinogen
2. GP1a-2a - collagen
2 main platelet non-integrins and ligans
- GP1b-9-5 - VWF
2. GP6 - collagen
funct. of dense granules
storage of small weight molecules - ATP, Ca, ADP
funct. of alpha granules
storage of proteins
- when activated, secreted
define MI vs. ischemic stroke
- MI in coronary art.
2. IS in carotid art.
what causes adhesion
break in endothelium
what happens during activation
secrete alpha and dense granules
what happens after activation
cascade to create thromboxane A2 (TxA2) -aggregating agent
what does aspirin do?
blocks COX-1 - an enzyme in cascade - can’t form TxA2
what does TxA2 do
flip is procoag. PS to outside - promotes coag.
what does PS on outside do
promotes platelets to aggregate together and form plug - primary hemostasis
what tells the platelets to adhere
platelet receptors binding to collagen and VWF
what is occuring in 2rd hemostasis
formation of fibrin strands - stabilize the 1st plug
what is common name of factor I
fibrinogen
common name for factor II
prothrombin
what factors are missing in hemophilia
A. factor VIII
B factor IX
4 factors that are vit. K dependant
II, VII, IX, X
what are the 2 groups of factors involved in coag.
- zymogens of serine proteases (enzymes_
2. cofactors - not enzymes
what defines an activaed factor
add an “a” factor II to IIa
2 main pathways of coag. cascade
- extrinsic
2. intrinsic
point where 2 pathways meet
Xa
what begins extrinsic cascade
tissue factor from damages cell wall
what does tissue factor activate in ext.
X to Xa
what does tissue factor activate in int.
IX to IXa
what starts intrinisic path
neg. charge surface contact phase
intrinsic path to Xa
HK>XII>XI>IX + VII (requires Ca)
what does Xa activate
prothrombinase > thrombin
what is co-factor for Xa
Va
2 main roles of fibrinogen
- aggregate platelets
2. fibrin cascade
factor involved in fibrinogen cascade
XIIIa
what activates XIII
thrombin
what 4 factors does thrombin feedback into
5,8,11,13
final product of cascade
cross-linked fibrin polymer - stabilizes clot
3 parts of cell-based model of coag.
- initiation
- amplification
- propagation
cascade of fibrinolysis
plasminogen>plasmin>lyses fibrin
major inhibitor of thrombin
antithrombin (75%)
what greatly potentiated antithrombin
heparin - use this an anticoagulant
