pathophysiology of congestion and oedema Flashcards
down what gradient does water (and all fluid in the body) flow?
pressure
what does Darcy’s law state and what does it mean phyiologically?
Q= change in pressure/resisitance
any changes in pressure or resistance of the cardiovascular system will result in a change in blood flow
what is congestion?
relative excess of blood in vessels of tissues or organ
does congestion involve active hyperaemia?
no
give an example of local acute congestion?
deep venous thrombosis
give an example of local chronic congestion?
hepatic cirrhosis
give an example of generalised acute congestion?
congestive cardiac failure
describe the pathophysiology of DVT causing infarction and ischaemia?
1.bloood backs up in the veins, venules and capillaries
2. decreased outflow of blood
3, local, acute congestion
4. decrease in pressure gradient
5. decrease in flow as a result of this
6. no O2 supply so ischaemia and infarction
what does hepatic cirrhosis result from?
serious liver damage from hepatitis B virus or alcohol
what is the pathophysiology of hepatic cirrhosis?
1, serious liver damage
- regenerating liver forms nodules of hepatocytes with intervening fibrosis
- this alters hepatic blood flow
- so causes congestion in portal vein and branches.
- increased portal venous pressure
- and there is an increase in collateral circulation
what are some consequences of portal-system hypertension?
blood is shunted to areas causing features like oesophageal varices and caput medisae
what is dangerous about oesophageal varices?
they only have a thin lining over them so can easily be ruptured, causing haemorrhage
what is congestive cardiac failure?
the heart is unable to clear blood from the right and left ventricles (the heart is an ineffective pump)
what is the pathophysiology of congestive cardiac disease?
- decrease in cardiac output
- decrease in renal glomerular filtration rate
- this causes the activation of the renin-angiotensin-aldosterone system
- this causes sodium and water retention
- therefore there is an increase in the amount of fluid in the body
- there is a fluid overload in the veins
what is the pathophysiology of pulmonary oedema caused by left ventricular failure?
- increase in left atrial pressure
- passive retrograde flwo to pulmonary veins, capillaries and arteries
- increase in vascular pressure
- increase in pulmonary blood volume
- increased hydrostatic pressure leads to increased filtration