Infarction

Question 1

definition

Answer 1

ischaemic necrosis due to partial or total occlusion of arterial or venous vessels

Question 2

aetiology

Answer 2

• trauma
• pulmonary function reduction
• embolism
• thrombus

Question 3

What does extent of damage depend on?

Answer 3

• tissue/organ
• time
• pattern of blood flow
• previous disease

Question 4

Development of infarction

Answer 4

Reduced blood flow- anaerobic metabolism- cell death-release of enzyme- tissue breakdown

Question 5

different types of necrosis

Answer 5

coagulative: e.g. in the heart- the architecture of the tissue is maintained a few days after necrosis
Colliquative: e.g. in the brain- tissue is broken down into a liquid mass

Question 6

Myocardial infarction development

Answer 6

Few seconds: anaerobic respiration- ATP depletion
Less than 2 mins: loss of contractility
Few mins: reversible ultrastructure changes
20-40 mins: myocyte necrosis
>1 hour: damage to microvasculature

Question 7

Visual changes in myocardial infarction

Answer 7

2-4 hours: no visible change
4-12 hours: swollen mitochondria on electron microscope
24-48 hours: pale infarct- solid tissues e.g. spleen, kidney, myocardium
red infarct- loose tissue, previously occluded e.g. lung, liver
microscopically: acute inflammation
>72 hours: pale infarct- yellow, white and red at borders
little change in red infarct
microscopically: chronic inflammation- macrophages phagocytise debris, granulation tissue, fibrosis

Question 8

pale infarct/ red infarct

Answer 8

pale: arterial occlusion
red: venous occlusion