thrombosis and embolism Flashcards
(35 cards)
what is a thrombus
a mass of normal blood constituents formed inappropriately within the circulation
what are the components in a thrombus
fibrin and platelets with entrapped RBCs and WBCs
thrombus structure
visible laminations (lines of Zahn) made of alternating platelets/fibrin with RBCs
what process if thrombosis identical to?
haemostasis
what is haemostasis and how does it happen
a phsyiological response to injury of BVs - loss of endothelial cells lining the BVs leads to exposure of the underlying collagen matrix, activating the platelets and forming a primary haemostatic plug; coagulation cascade is activated and thrombin is produced; fibrin is deposited around fused platelets producing a secondary haemostatic plug
what are the 3 main components of controlled haemostasis
endothelial cells; platelets; coagulation system
what anti-thrombotic factors are normally secreted by endothelial cells (5)
anti-platelet: prostacyclin, nitric oxide
anti-coagulant: antithrombin III, thrombomodulin-activated proteins C/S
profibrinolytic: tissue plasminogen actvator (tPA)
what is the platelet adhesion factor
GpIb gylcoprotein binding to Von Willebrand factor on BV wall
what are 2 platelet release factors
fibrinogen; PDGF
what are 2 platelet aggregation factors
thromboxane A2, ADP
what is virchow’s triad
predisposing factors for thrombus formation
1. change of blood flow (stasis)
2. vessel wall injury
3. hypercoaguable state (blood constituents change)
what can disruption of laminar flow cause (in relation to thrombus formation - 3)
platelets to come into contact with endothelium; injury/activation of endothelium; impaired removal of pro-coagulant factors/impaired delivery of anti-coagulant factors
what can cause altered blood flow (5)
narrowing caused by atherosclerosis; aneuyrsm; infected myocardium; abnormal cardiac rhythm; valvular heart disease (regurge and stenosis can cause)
what occurs to the myocardium post MI and where
subendocardial and transmural fibrosis - does not contract (these areas are hypodynamic)
what normally causes altered blood flow in veins
stasis
what are the 2 vein areas blood flow is most common;y altered in
pelvic; superficial leg
what can cause blood stasis in veins (5)
right sided HF; immobilisation; compressed veins (bed rest); varicose veins; increased blood viscosity (aneamia, dehydration etc.)
what can cause endothelial cell injury/activation (5)
ischaemic hypoxia; infection of BVs; physical (hypertension, crushed veins etc.); chemical (lipids, cigs etc.); immunological deposition of immune complexes
what can cause changed in vessel walls
damage to endothelium by atheroma; coronary artery thromobosis; MI
what can cause changes in blood constituents
genetic: antibrombin III deficiency, protein C;
acquired: tissue damage, post-op, malignancy, cig smoke, elevated blood lipids, oral contraceptives
possible fates of a thrombus pathway (2)
thrombus -> remains attached -> lysis/retraction/organisation/infection;
thrombus -> primary detachment -> emboli
what is an embolus
an abnormal mass of undissolved material which is transported from one part of the circulation to another
types of emoblus (5)
thrombus; gas (air, nitrogen); fat; tumour; misc (foreign bodies, amniotic fluid etc.)
what can occur with venous emboli (pulmonary arteries)
lodge in pulmonary arteries - hypoxia, decr CO, pulomary infarction, pulmonary hypertension, right HF, death
