Blood, defence and circulation
Red cells carry oxygen, white cells fight pathogens, and cardiac output is stroke volume multiplied by heart rate.
A worked example
A heart beating 62 times a minute at 80 mL per beat has a cardiac output of 62 x 80 = 4 960 mL/min, about 5.0 L/min.
The mistake people actually make
Antibodies bind to a specific antigen and mark the pathogen for destruction; they do not destroy it themselves. Smoking, saturated fat and high blood pressure raise cardiovascular risk, while exercise lowers it.