Compare and contrast stenosis and regurgitation (insufficiency) in terms of the functional abnormality associated with the valve leaflets and their effects on hemodynamic parameters such as stroke volume.
stenosis means thats it difficult to open the valve to allow a full ejection of blood. regurgitation is caused by an insufficient valve, in which the valve does not close all the way, and thus allows blood to flow backwards. For instance, the two AV valves (mitral on the left, tricuspid on the right), are prevented from prolapsing by chordae tendonae, which are connective tissue fibers attached to pieces of cardiac muscle (papillary muscles) on one end, and the edge of the valve on the other. If these chordae tendonae break, this may cause blood to flow back into the respective atria during ventricular systole. Valvular insufficiency and prolapse will cause diminished stroke volume. Valvular stenosis, on the other hand, is typically caused by a buildup of material on a valve which inhibits its movement. This buildup could be many different things, to name a few: valve calcification due to hypercalcemia, bacterial adhesion and growth due to sepsis, plaque (cholesterol bound with free radicals) buildup on the valve, a fibroma, etc... If the valve's opening is inhibited, and it does not open all the way, there will be a diminished blood flow into whatever chamber is next in the sequence. If an AV valve is stenotic, the ventricles may not fill properly, and preload will be low, which will lower ejection volume. If the semilunar valves are stenotic, then the ventricles will likely hypertrophy because they will need to work harder to force as much blood out, because blood entering the ventricle must equal blood leaving the ventricle with each heartbeat (starlings law of the heart).
