The blood comes from the body's reservoirs:
spleen (mostly erythrocytes) 
veins (probably the most important blood resevoir as they contain 50-60 % of the volume) 
In pathological situations, if hypovolemia occurs, blood can also come from:
splachnic vascular bed 
But what attracts the blood into the muscle? The phenomenon is called ...
How does extra blood come from to fill your muscles during exercise?
Blood pumps (blood) and sucks (lymph).
There are many pumps in our body
which work together to provide the blood to the peripheral circulation.
These pumps provide us Pulse, Vasomotor tone and Respiratory waves which when act together ...
If you stand up too quickly, you get a head rush. One way to counteract the symptoms of the head rush is to contract your leg muscles really intensely. This forces blood out of your legs and into the rest of your circulation, including your head. This is actually a tip my family doctor told me that I've always remembered.
As mentioned in the links below ...
I think CVC lead to Pulmonary congestion and edema.
They produce heavy, wet lungs.
Pulmonary changes include
perivascular and interstitial edema, particularly in the interlobular septa;
progessive edematous widening of alveolar septa; and
accumulation of edema fluid in alveolar spaces which contain Hemosiderin and microhemorrhages
Now, the progression ...