Veins Carry Blood Back Toward the HeartĪfter the capillaries release oxygen and other substances from blood into body tissues, they feed the blood back toward the veins. This structure allows arteries to dilate as blood pumps through them. The walls of arteries are thicker than the walls of veins, with more smooth muscle and elastic tissue. The arterioles branch into the capillary networks that supply tissues with oxygen and nutrients. From there, blood passes through major arteries, which branch into muscular arteries and then microscopic arterioles. The left ventricle of the heart pumps oxygenated blood into the aorta. Oxygenated Blood Flows Away from the Heart Through Arteries These layers surround the lumen, the hollow interior through which blood flows. The walls of most blood vessels have three distinct layers: the tunica externa, the tunica media, and the tunica intima. The capillaries also connect the branches of arteries and to the branches of veins. Capillaries surround body cells and tissues to deliver and absorb oxygen, nutrients, and other substances. Veins return blood back toward the heart. Arteries transport blood away from the heart. The Three Major Types of Blood Vessels: Arteries, Veins, and Capillariesīlood vessels flow blood throughout the body. That’s enough to circle the earth almost three times! 1. If you were to lay out all the blood vessels of the body in a line, they would stretch for nearly 60,000 miles.
These arteries, veins, and capillaries make for a vast network of pipes. The journey might begin and end with the heart, but the blood vessels reach every vital spot along the way. Blood flowing through the circulatory system transports nutrients, oxygen, and water to cells throughout the body.
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