The purpose of the cardiovascular system is to provide the body's
cells with oxygen and nutrients and remove waste. Its components
are the heart, arteries, arterioles, capillaries, veins and venules.
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Elaboration — More on Arteries, Arterioles and Capillaries
Arteries are vessels that carry
blood away from the heart. They branch out and become
smaller as they reach out into the body. Arteries
have thicker walls than veins.
Arterioles are the small terminal
branches of an artery that connect with a capillary.
Capillaries are vessels with many
branches. Slow blood flow and thin walls make capillaries
effective in exchanging water, food and wastes.
Veins are vessels that carry
the blood to the heart. Large veins, such as those
in the abdomen, contain smooth muscle that can contract
to propel blood toward the heart. A small amount
of cardiac muscle is present in the vena cava and
pulmonary veins as they join the heart.
Small and medium sized veins have valves to prevent
backflow. Veins with valves are prevalent in the
extremities where contraction of skeletal muscle
helps to propel the blood toward the heart.
Venules are small veins that
connect capillaries to larger veins.
