There are four major components of the cadiovascular, or circulatory system: Heart Arteries Veins Capillaries Two major circuits or pathways of blood flow: Systemic - carries oxygenated blood to the body Pulmonary - carries deoxygenated blood to the lungs, and returns oxygenated blood to the heart Different Pump Systems: FISH: Blood flows from ventricle, to gills, then directly to rest of the body before coming back to the heart --&gt; simple loop system AMPHIBIANS: Blood leaving ventricle is split between going to respiratory surfaces (pulmonary) and to the body (systemic) * First development of a double circulatory system: Amphibian system is inefficient: Ridges in ventricle reduces mixing of blood REPTILES: Little mixing of oxygen rich and oxygen poor blood --&gt; increased efficiency --&gt; supports more active lifestyle MAMMALS and BIRDS: Complete separation of pulmonary and systemic blood flow: - more oxygen available for delivery to the body ** Mammals : right side of heart --&gt; left side of heart --&gt; Birds : right side of heart --&gt; left side 
(Systemic; carries; oxygenated blood) (Blood; leaving; ventricle) (Amphibian system; is; inefficient) Context(Amphibian system is,List([633, 652))):(returns; oxygenated; blood) (Pulmonary; carries; deoxygenated blood)
Amphibian system is,List([633, 652))
Systemic Blood Amphibian system returns Pulmonary
carries leaving is oxygenated carries
oxygenated blood
ventricle
inefficient
blood
deoxygenated blood