THE ARTERIES AND VEINS

Your arteries and veins are essential for carrying the blood pumped by the heart to and from all parts of the body. The arteries carry blood away from the heart, and the veins bring blood back to the heart from the tissues in the body.

The arteries can be thought of as a "tree" in which a trunk branches into smaller and smaller branches and twigs (arterioles) until they finally become capillaries. Capillaries are only slightly wider than a single blood cell. Thus, they allow only a single-file column of blood cells to travel through at a time. It is through the thin wall of the capillaries that oxygen, carbon dioxide, nutrients, and waste products are exchanged (see Figures 7 and 9, page A3).

After the blood flows through the capillaries, it enters small veins (venules) that merge into larger and larger branches (veins) that go back to the atria.

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Cardio & Blood