Haemostasis Flashcards
What is haemostasis
Process which forms blood clots at endothelial damage and vascular injury sites. Also involves lot removal post-repair
Haemostasis defect result
Uncontrolled bleeding
Overactive haemostasis result
Abnormal clots (thrombi) can lead to tissue ischaemia and cell death
Intact endothelial fx
Repel platelets
Prevent platelet-sub endothelial ECM contact
Synth NO and PGI2
Endothelium activated to be procoagulant by
Direct injury
Cytokine heamodynamic forces
Infectious agents
Plasma mediators
What causes the main vascular response of vasoconstriction?
Local neural reflexes and vasoactive substances released from endothelium and platelets (eg endothelin)
Describe platelets
Small anuclear disc shaped fragments
Produced by megakaryocyte in the bone marrow
VWB factor fx
Form bridge between subendo collagen and platelet receptors to allow platelet adhesion
Factors in platelet granules
5 Calcium ADP P selectin Fibrinogen
Platelet aggregation stimulated by
ADP
thromboxane 2
What is wrong with the primary haemostasis plug
Loose, could easily be washed away by blood flow
Factor 12 aka
Hageman factor
Trigger of intrinsic system
Blood exposed to surfaces other than normal endothelium. Activation of 12 in plasma is what other factors are derived from
Entrinsic system triggered
Vascular damage which exposes tissue factor (3)
3 may also be induced by cytokines (TNF, IL1, bact endotoxin)
Faster system
Extrinsic
Thrombin produced triggers intrinsic - by passing 12.
Anti-inflamm drugs affect
Affect TXA2 and PGI2 conc so alter clot risk (decr TXA2 decr risk, decr PGI2 incr risk)
Site of fibrinogen synthesis
Liver. Present in normal animal blood
Half life 2-4d
States that increase fibrinogen
Pregnancy
Disease states
Where is 13 released from
Entrapped platelets
Means of tight regulation of cascade and confinement
Endo repel clotting factors and prevent 12 activation
Cascade only occur at site of damage as need exposed phospholipids
Endogenous anti-coags eg anti-thrombin 3
Factors req vit K as co factor for synth
2
7
9
10
Warfarin and related anticoag method
Antagonise vit K
Red vit K bioavailability
How to prevent clotting in blood sample
Chelate calcium
What is tissue factor
A procoagulant glycopro
