Blood cells 1 - ghghg PDF

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First step: The heart The left ventricle contracts, pushing the blood cells into the aorta, which is the body's largest artery. From here on, the blood cells move into increasingly smaller arteries until it reaches the capillaries. The capillaries is the junction between the arteries and veins; here the oxygen molecules detach from the red blood cells and slip across the capillary wall into body tissue. Now de-oxygenated, blood begins its return to the heart. It passes through increasingly larger veins to eventually reach the right atrium. It enters the right ventricle, which pumps it through the pulmonary arteries into the lungs, to pick up more oxygen. Next step: The body If we start from the heart, red blood cells first make their way through a large artery called the pulmonary artery toward the lungs where they pick up all the oxygen they're going to need for their long journey through the body. They then come back to the heart where they're pumped into a super-large blood vessel called the aorta. From there, many branches called arteries take the blood to all the different locations in the body, like your arms, legs, stomach, intestines and so on. When they get to those places, the arteries become smaller and smaller until they become what we call capillaries. There, the blood cells start marching single file and give all their oxygen away to those organs. They then head home on little veins which grow larger as they head toward the heart. Before they get all the way back, however, they pass through our liver and our spleen. The spleen gets rid of all the old red blood cells that aren't working so well anymore, and the liver does so too, but to a lesser extent. Finally, they head back into the heart through large veins called the vena cava. They then do the whole thing all over again...