Hematology Flashcards
tunica intima layer
barrier of endothelial cells in the vasculature; produces procoagulants and anticoagulants mediators, and fibrinolytic
procoagulant mediators
von willebrand factor,
tissue factor (TF),
thromboxane A2 and Adenosine diphosphate (ADP),
collagen,
fibronectin
anticoagulant mediators
nitric oxide (NO),
prostacyclin,
prostaglandin I2
von Willebrand factor (vWF)
cofactor for coagulation cascade
tissue factor (TF)
activates clotting cascade pathway during vessel injury
thromboxane A2 and adenosine diphosphate (ADP)
vasoconstriction
collagen
stimulates platelet attachment to the injured vessel wall
fibronectin
facilitates anchoring of fibrin during the formation of a hemostatic plug
nitric oxide (NO)
inhibits platelet adhesion and aggregation;
promotes vasodilation (smooth muscle relaxation)
prostacyclin
causes vasodilation and interferes with platelet formation and aggregation
prostaglandin I2
inhibits platelets
Primary hemostasis (platelet plug)
no injury - nitric oxide and prostaglandin I2 releases which inhibit platelets
INJURY - thromboxane A2 releases which causes vasoconstriction; platelet plug is formed through adhesion, activation, and aggregation of platelets
Adhesion (primary hemostasis)
- collagen exposed
- vonWillebrand factor released and binds to Gplb receptors on the platelet which anchors the platelets of the sub endothelium
- platelets bind to the collagen and are activated
Note:
1. desmopressin causes the body to release more vWF
2. FFP and Cryo also help with this step bc they contain vWF and Factor 8
Activation (primary hemostasis)
- platelets are activated by binding to collagen
- the platelets then release thromboxane A2 and ADP which activates other platelets and help with aggregation by allowing glycoproteins on platelets to bind to fibrinogen.
- activated platelets will release contents from inside them such as fibrinogen, fibronectin, and vWF.
aggregation (primary hemostasis)
- activated platelets have 2 glycoproteins on their surface - Gp IIIa and Gp IIb
together they help aggregate platelets to form a “plug”