DON W. FAWCETT / SCIENCE PHOTO LIBRARY DON W. FAWCETT / SCIENCE PHOTO LIBRARY
Photomicrograph of the specialized veins of the penis believed to be involved in the hemodynamics of erection. Shown here is a cross section through a circumflex vein at the distal end of the corpora cavernosa, showing thick muscular pollsters, indicated by arrows. Magnification 40x at approximately 4.5x3 inches.
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