Ischaemia and infarction

Question 1

Definition of ischaemia

Answer 1

Impaired blood supply to an organ resulting in hypoxic damage( impaired oxygen delivery~~failed energy production~~functional changes~~morphological changes) to susceptible cells

Question 2

Discuss in detail: the functional changes associated with ischaemia on a cellular level

Answer 2

1. Mitochondrial phosphorylation ceases due to oxygen lack, which leads to depletion of creatine phosphate and ATP.
2. Anaerobic glycolysis commences
3. Substrate stores of glycogen and glucose are used up because of disturbed blood supply
4. Anaerobic glycolysis ceases- Inhibited by low levels of ATP.
5. Na and K pump failure- Na ions enter cells followed by H2O

Question 3

Discuss in detail the morphological changes associated with ischaemia

Answer 3

1.Mitochondrial swelling
2.Intracellular oedema
3. Cell Necrosis
4. Inflammatory response

Question 4

Discusss types of ischaemia with examples

Answer 4

2 Types Generalised, temporary and Local, Chronic

Generalised , Temporary
.this is due to shock, myocardinal arrest or fibrillation, effect of this are felt in organs which are most susceptible to O2 tension i.e. the brain and the heart.

Local, chronic
.) Cardiac
Causes:
incomplete occlusion of the coronary vessels due to atheroma
spasm of vessel (thromboxane A2)
arteritis
Clinical effects: angina pectoris
Macroscopy: smaller involuted organ
b) Limb ischaemia
Causes:
atheroma
Buerger’s disease
Clinical effects: Intermittent claudication (pain in limb on exercise, relieved by rest).
c) Bedsores
Mechanical compression of blood vessels  compromised flow over bony prominences

Question 5

Define infarction

Answer 5

A localized area of ischaemic necrosis in an organ or tissue resulting from either arterial or venous occlusion.

Question 6

Outline the pathogenesis of infarction

Answer 6

We have three pathogenesis for infarction. namely arterial occlusion, arterial narrowing and venous occlusion.
Arterial occlusion- this may be caused by thrombosis or embolism, but the effect is dependent on the anatomic pattern of arterial supply.
Arterial narrrowing- this may be caused by endarteritis obliterans and atheromatous deposition in the wall. thyis might lead to frank infaction or ischaemic effect.
Venous occlusion- this leads to a decrease in the outflow of blood causing an increase in pressure.

Question 7

Classify types of infarction

Answer 7

We have three types of infarcts, White/pale infarcts, red/haemorrhagic infacts and septic infarcts.

White/pale infarcts -are observed when there is a complete occlusion of arterial supply in organs with an end arterial supply(meaning that the arteries that have been occluded are the only one who were providing supply of blood to that organ)

red/haemorrhagic infarcts- Marked by swollen necrotic tissue which is red due to numerous blood cells

Septic Infarcts- Bacterial contamination of an infarcts.

Question 8

Describe possible macroscopic and microscopic appearance of infarcts

Answer 8

Macroscopic
.Wedge-shaped
.Early infarct- Dark and firmer than surrounding
.Later lesions-either white/pale infarcts or red/haemorrhagic infarcts

Microscopic appearance

Question 9

List factors which can modify the effects of vascular occlusion

Answer 9

General status of blood and CVS
Anatomic pattern of arterial supply
Rate of occlusion
Vulnerability of tissue