Module 3: Mechanisms of Normal Hemostasis (from review sheet) Flashcards
Hemostasis
prevention and arrest of bleeding by rapid repair of nay ruptures in blood vessels
5 components of hemostasis
vascular platelet coagulation system fibrinolytic system natural anticoagulants and inhibitors
3 things secreted by endothelial cells that make them thromboresistant
heparin sulfate
Prostacyclin
nitrous oxide
2 types of vasoconstriction after injury
muscular humoral (delayed due to release of endothelin)
endothelin
secreted by endothelial cells
induces smooth muscle contraction for vasoconstriction
2 things released by injured tissue
Tissue thromboplastin (III) Tissue Plasminogen Activator (TPA)
Tests for vascular response (3)
bleeding time
closure test
capillary fragility test
why is Thrombopoiesis different from other cells (2)
megakaryocytic get bigger as they mature
no cellular division
platelet lifespan in blood
8-10 days
3 zones of platelet
peripheral
sol gel
organelle
peripheral zone
plasma membrane
outer coating
glycocalyx
Important for adhesion and aggregation
Sol gel zone
cytoskeleton with contractile proteins thrombosthenin and actomyosin
importnat in plt retraction, shape changes, viscous metamophosis in secondary aggregation
Organelle zone
canicular system, dense bodies, alpha granules (PF3, fibrinogen, thrombospondin, PF4), dense tubular system (stores Ca2+)
Important in plt retraction and prostaglandin synthesis
% of platelets in circulation
70%
% of platelets in spleen
17%
% of platelets in liver, lungs, bone marrow
13%
Platelet factor
substance absorbed onto the plt membrane or carried in the plt granules that are released during the release reaction and that influence homeostasis
PF1
absorbed coagulation factor V
PF2
fibrinogen activating factor
PF3
platelet phospholipid
acts as organization surface to bring required factors into close proximity and facilitate reaction
PF4
anti-heparin factor
glycoprotein that inhibits the reaction of heparin
Platelet functions (2)
hemostatic functions (plug, adhesion, aggregation and retraction) Thromboplastic (actual clot, plt releases chemicals that reinforce vasoconstriction, aggregation and coagulation reactions that promote growth and healing)
platelet adhesion requires (2)
GPIb
vwF
Primary aggregation requires (4) - reversible
ADP
GIIb/IIIa
Ca2+
Fibrinogen