BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY
Artery and vein. Light micrograph of a transverse- section through an artery (at left) and a vein (at right) in a tissue sample. The wall of the artery is thick (yellow) made up of smooth muscle with elastic fibres. This enables the artery to expand and withstand sudden pulses of blood. Blood is seen in the inner lumen of the artery. The vein has thin walls and a wider lumen; two clusters of blood are visible. Veins transport blood at low pressure and hence need a less contractile wall and a wider lumen. Arteries carry oxygenated blood pumped from the heart to the body's tissues, while veins return "used" deoxygenated blood to the heart and lungs. Magnification: unknown.
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