Individuals who want to donate whole blood or apheresis must be : At least 16 years old (donors under the age of 17 may only donate whole blood, and must have a signed parental/guardian consent form). At least 19 years old and weigh a minimum of 110 pounds.
Your heart handles blood in much the same way. The heart pumps about 2,000 gallons (7,571 liters) of blood a day through its chambers. Of Â­course, we're not big enough to hold that much liquid, so it just pumps the same blood over and over, and it doesn't benefit from a drop of it. At least, not initially.
The heart pumps blood in a two-step process. The atria pump blood into the ventricles and then the ventricles pump blood out of the heart. Chambers of the heart fill with blood during a relaxation phase (diastole) and eject blood during a contraction phase (systole). Atrial systole precedes ventricular systole.