[A] 1.18 Local oligaemia (ischaemia) Flashcards
Ischaemia
Local inadequate blood supply
- General:
- Anaemia
- Hypovolaemia
Physiological ischaemia
- Digestion
- Uneven distribution of blood
Pathological ischaemia
- Compression
- Obturation
- Vasoneurotic disturbances
Ischaemia compressiva
- Tympany (horse, cow, rabbit)
- Tumours
Ischaemia obturativa
- Thrombus
- Embolus
Vasoneurotic ischaemia
Angiospasm
CNS, cold, chemicals
The consequences of ischaemia depends on…
- Degree and type of narrowing
- Time
- Type of tissue
- Collaterals (Lung, liver)
How the tissue type alters the impact of an infarction
- End arteries → No anastomotic channel → Infarct
- Anastomotic arteries → Blood flow can still occur (Kidneys)
Give the consequences of ischaemia
- Collapse/shock
- Necrosis:
- Infarctus haemorrhagicus
- Infarctus ischaemicus
Infarction: Definition
Necrosis of circumscribed area of tissue due to acute ischemia
Vessels are obturated
Ischemic infarction: End arteries
- Appearance
- Area becomes bloodless, necrotic
- Appearance:
- Pale grey, dry
- Margin of infarction is reddish
- The collateral vessels are full with RBCs
Locations of ischemic infarction
- Kidneys
- Heart
- Spleen
- Brain
Formation of the infarction
- Pale, swollen, no sharp edges
- Histochemical methods are needed for demonstration
Haemorrhagic infarction
Double circulation
- In the necrotic area, the vessels are filled with RBCs
- Red (darker), dry
Fresh infarction: appearance
- Cone shaped
- Pale
- Enlarged
- Sharp edged
- Cut surface is still moist
Evolved infarction: Appearance
- Cur surface dry
- Homogenous
- Crumbled
- Dark red
- Hyperaemic rim
Older/chronic infarction: appearance
Surrounded by demarcation zone, scar
Haemorrhagic infarction: Location
- Lungs
- Kidney
- Spleen
- Liver
List the factors impacting on infarction
- Nature of vascular supply
- Rate of occlusion development
- Vulnerability to hypoxia
- Oxygen content of the blood
Nature of vascular supply: Factor of infarction
- Double (lungs, liver)
- End-arterial (kidney, spleen)
Rate of occlusion development: Effect of infarction
If it is slow, collateral blood supply may develop
Vulnerability to hypoxia: Impact on infarction
- Neurons = 3-4 mins
- Myocardial cells = 20-30 mins
- Fibroblasts = Hours
Give the consequences of an infarction
- Death
- Insufficient heart & lung supply/function
- Survival
- Reactive inflammation
- Repair
- Organisatio - Connective tissue
