Thrombosis and embolism

Question 1

Describe a thrombus

Answer 1

mass of normal blood constituents formed inappropriately within the circulation during life
composed of fibrin and platelets with entrapped red and white blood cells

Question 2

What are Lines of Zahn?

Answer 2

characteristic of thrombus formed at the site of rapid arterial blood flow, with laminations produced by successive deposition of platelets and fibrin (pale layers) alternating with red blood cells (dark layers)

Question 3

How does haemostasis happen?

Answer 3

injury to blood vessels leads to loss of the lining endothelial cells, which normally prevent haemostasis

exposure of underlying extracellular matrix (collagen), activates platelets forming a primary haemostatic plug

coagulation cascade activated

thrombin produced, fibrin deposited around fused platelets, producing secondary haemostatic plug

Question 4

Where are platelets produced?

Answer 4

by megakaryocytes in bone marrow

Question 5

List Virchow’s triad

Answer 5

venous stasis
hypercoagulability
endothelial/vascular injury

Question 6

Causes of altered blood flow in a vessel?

Answer 6

narrowing due to atherosclerosis
aneurysms
infarcted myocardium
abnormal cardiac rhythm
valvular heart disease

Question 7

What can cause altered blood flow in veins?

Answer 7

usually due to stasis

failure of right side of heart
immobilisation
compressed veins (eg. bed rest)
varicose veins
increased blood viscosity (eg. sickle cell anaemia, dehydration)

Question 8

What is an embolus?

Answer 8

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

Question 9

Name some types of embolus

Answer 9

thrombus
gas - air, nitrogen
fat
tumour
miscellaneous - foreign bodies (drug addicts)

Question 10

What is the effect of an embolus lodging in the pulmonary artery?

Answer 10

hypoxia
reduced cardiac output
pulmonary infarction
pulmonary hypertension
right heart failure
death

Question 11

What is a saddle embolus?

Answer 11

occludes both pulmonary arteries

Question 12

What is a paradoxical embolus?

Answer 12

passes through interatrial or interventricular cardiac defect to gain access to systemic circulation

Question 13

When can fat embolisms occur?

Answer 13

fracture of long bones
soft tissue trauma
burns

Question 14

When can a nitrogen embolus occur?

Answer 14

in deep sea divers on rapid ascent

• decompression sickness or the bends

Question 15

Symptoms and signs of fat embolism

Answer 15

tachypnoea
tachycardia
dyspnoea
irritability
restlessness
diffuse petechial rash
thombocytopenia