SUSUMU NISHINAGA / SCIENCE PHOTO LIBRARY SUSUMU NISHINAGA / SCIENCE PHOTO LIBRARY
Heart valve and strings, coloured scanning electron micrograph (SEM). This is the mitral valve (upper right), controlling the blood flow between two of the heart's chambers, the left atrium (not seen) and the left ventricle (seen here). The heart strings (thread-like structures) are known as the chordae tendineae, and are controlled by the papilliary muscles (one at lower right). The structures at centre, known as trabeculae carneae, are muscular, columnar protrusions found on the internal surface of the ventricles.
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