Cardiac Pathology Flashcards
What is oedema? Explain how it is caused.
Oedema is an accumulation of fluid in the interstitial space. It can be caused by: (1) alterations in Starling’s forces - either an increase in the capillary hydrostatic pressure or a decrease in the plasma oncotic pressure; (2) an obstruction to lymphatic drainage or (3) an increase in vascular permeability.
What are hyperaemia and congestion?
In both hyperaemia and congestion, there is an increased amount of blood in the vessels of an organ/tissue. In hyperaemia, this is an active process = it is accompanied by an increase in blood flow. In congestion, I this is a passive process = it is caused by an obstruction to the outflow of blood.
What is Virchow’s Triad?
Virchow’s triad explains the 3 major abnormalities that cause thrombosis. These are: (1) endothelial injury; (2) hypercoagulability of the blood; (3) abnormal blood flow - either stasis or turbulence.
What are the macroscopic and microscopic features of a thrombus?
Macroscopic: there is solid or semi-solid material present in the vessel lumen; material is red-brown and friable; it extends along the vessel in the direction of blood flow.
Microscopic features: platelet aggregation with the deposition of fibrin (platelets are dominant in arteries and fibrin is dominant in veins); there may be alternating layers called ‘lines of Zahn’.
What are the 4 fates of a thrombus?
(1) Propagation –> with progressive occlusion of the vessel.
(2) Detachment –> with embolization.
(3) Dissolution –> by the action of fibrinolytic enzymes.
(4) Organisation and recanalization –> new channels form through the thrombus.
What is an embolus?
An embolus is a detached intravascular solid, liquid or gaseous mass that is carried by the blood from its point of origin to a distant site.