thrombosis and embolism

Question 1

what is a thrombus

Answer 1

a mass of normal blood constituents formed inappropriately within the circulation

Question 2

what are the components in a thrombus

Answer 2

fibrin and platelets with entrapped RBCs and WBCs

Question 3

thrombus structure

Answer 3

visible laminations (lines of Zahn) made of alternating platelets/fibrin with RBCs

Question 4

what process if thrombosis identical to?

Answer 4

haemostasis

Question 5

what is haemostasis and how does it happen

Answer 5

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

Question 6

what are the 3 main components of controlled haemostasis

Answer 6

endothelial cells; platelets; coagulation system

Question 7

what anti-thrombotic factors are normally secreted by endothelial cells (5)

Answer 7

anti-platelet: prostacyclin, nitric oxide
anti-coagulant: antithrombin III, thrombomodulin-activated proteins C/S
profibrinolytic: tissue plasminogen actvator (tPA)

Question 8

what is the platelet adhesion factor

Answer 8

GpIb gylcoprotein binding to Von Willebrand factor on BV wall

Question 9

what are 2 platelet release factors

Answer 9

fibrinogen; PDGF

Question 10

what are 2 platelet aggregation factors

Answer 10

thromboxane A2, ADP

Question 11

what is virchow’s triad

Answer 11

predisposing factors for thrombus formation
1. change of blood flow (stasis)
2. vessel wall injury
3. hypercoaguable state (blood constituents change)

Question 12

what can disruption of laminar flow cause (in relation to thrombus formation - 3)

Answer 12

platelets to come into contact with endothelium; injury/activation of endothelium; impaired removal of pro-coagulant factors/impaired delivery of anti-coagulant factors

Question 13

what can cause altered blood flow (5)

Answer 13

narrowing caused by atherosclerosis; aneuyrsm; infected myocardium; abnormal cardiac rhythm; valvular heart disease (regurge and stenosis can cause)

Question 14

what occurs to the myocardium post MI and where

Answer 14

subendocardial and transmural fibrosis - does not contract (these areas are hypodynamic)

Question 15

what normally causes altered blood flow in veins

Answer 15

stasis

Question 16

what are the 2 vein areas blood flow is most common;y altered in

Answer 16

pelvic; superficial leg

Question 17

what can cause blood stasis in veins (5)

Answer 17

right sided HF; immobilisation; compressed veins (bed rest); varicose veins; increased blood viscosity (aneamia, dehydration etc.)

Question 18

what can cause endothelial cell injury/activation (5)

Answer 18

ischaemic hypoxia; infection of BVs; physical (hypertension, crushed veins etc.); chemical (lipids, cigs etc.); immunological deposition of immune complexes

Question 19

what can cause changed in vessel walls

Answer 19

damage to endothelium by atheroma; coronary artery thromobosis; MI

Question 20

what can cause changes in blood constituents

Answer 20

genetic: antibrombin III deficiency, protein C;
acquired: tissue damage, post-op, malignancy, cig smoke, elevated blood lipids, oral contraceptives

Question 21

possible fates of a thrombus pathway (2)

Answer 21

thrombus -> remains attached -> lysis/retraction/organisation/infection;
thrombus -> primary detachment -> emboli

Question 22

what is an embolus

Answer 22

an abnormal mass of undissolved material which is transported from one part of the circulation to another

Question 23

types of emoblus (5)

Answer 23

thrombus; gas (air, nitrogen); fat; tumour; misc (foreign bodies, amniotic fluid etc.)

Question 24

what can occur with venous emboli (pulmonary arteries)

Answer 24

lodge in pulmonary arteries - hypoxia, decr CO, pulomary infarction, pulmonary hypertension, right HF, death

Question 25

what is a saddle embolus

Answer 25

an emblus that occluded both pulmonary arteries

Question 26

what is a paradoxical embolus

Answer 26

embolus that passes thrugh an interatrial/ventricular defect to gain access to systemic circulation

Question 27

what can an infected embolus lead to

Answer 27

pyaemia; abcess formation

Question 28

effects of arterial emboli

Answer 28

bacterial endocarditis; vegetation on inner surfaces of aortic valves; infarction

Question 29

when can an air embolus form and why is it significant

Answer 29

during obstetric procedure, chest wall injury; bubbles coalesce to form frothy masses which can occlude major vessels

Question 30

what is caisson disease

Answer 30

decompression sickness - persistent gas emboli in skeletal system leads to necrosis in the heads of femur, tibia and humerus

Question 31

when can fat emboli occur

Answer 31

long bone fracture; soft tissue trauma; burns;

Question 32

what can fat emobli cause

Answer 32

tachypnoea/tachycardia/dyspnoea; irritability; restlessness; thrombocytopeoenia; petichial rash

Question 33

what can exaggerate fat emboli

Answer 33

platelet/erythrocyte aggregation

Question 34

what can cause endothelial damage

Answer 34

release of free fatty acids

Question 35

how can an amniotic embolus occur

Answer 35

infusion of fluid into maternal circulation from placenta tear/rupture of uterine veins