the circulatory system is made up of the heart and a network of _,_,_,_,_,that distribute _,_,_,_,_,to the body in the form of blood containing dissolved _,_,_,_, _,_,_,_,_,_,carbon dioxide and_,_,_,_,_,_,_,_,_,_, Blood flows into the heartthrough the _,_,_,_,_, and out of the heart through the _,_,_,_,_.the flow of the heart, creating a force against the arterial walls. for this reason, the walls of the arteries are thick and _,_,_,_,_,_,_. in order to absorb the blood _,_,_,_,_,_,_,_.the vain and other hand, have thinner wall in as much as most of the pressure is lost in the capilaries.instead they are equiped with _,_,_,_,_,_,_,_,_,__,_, to prevent the backflow of blood . Arteries and veins are connected by microscope luber called _,_,_,_,_,_,_,_,_,_,_,. It is here where dissolvec flood and gasses are exchanged between the blood ad the _,_,_,_,_.

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