circulatory system
The human circulatory system functions to transport blood and oxygen from the lungs to the various tissues of the body
arteries carry blood away from the heart
veins are blood cells that bring blood back to the heart and drain blood from organs and limbs
capillaries have one layer of cells where diffusion and exchange of materials occur
blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. As the atrium contracts, blood flows from your right atrium into your right ventricle through the open tricuspid valve
some disorders of the circulatory are heart attacks and strokes when the heart works to much and starts to fail