1. Transport oxygen to tissue
2. Transport carbon dioxide away from tissue
1. Fight infection via neutrophils
2. Fight infection via immune system: (lymphocytes, monocytes, basophils, and eosinophils)
3. Fight parasitic infection via eosinophils
1. Plug leaks in the vascular system
2. Initiates clotting mechanism
3. Nourishes the endothelial cells