structures connect the arteries and veins?
vessels transport blood away from the heart and have thick muscular walls?
vessels transport blood toward the heart and have valves?
part of the heart receives blood from the lungs?
the circulatory system important to humans?
carries the oxygen around the body
system that ensures all cells nutrients
hormones throughout the body
structures are included in the circulatory system?
capillaries small and thin?
blood cells can collect as much oxygen as possible when hey travel through them.
that enter or leave the bloodstream must diffuse through membrane. The thin
nature of these vessels ensures efficient diffusion.
parts of the heart. Why do you suppose the heart needs all these parts?
Right atriums, left + right ventricles
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