PROFF. P. MOTTA / G. MACCHIARELLI / UNIVERSITY "LA SAPIENZA", ROME / SCIENCE PHOTO LIBRARY PROFF. P. MOTTA / G. MACCHIARELLI / UNIVERSITY "LA SAPIENZA", ROME / SCIENCE PHOTO LIBRARY
Heart valve. False-colour scanning electron micrograph of the aortic valve (bottom centre). It lies between the left ventricle of the heart and the aortic arch and consists of a fibrous annulus (ring) which has three semilunar pockets attached to it. In the diastole phase the aortic valve is closed maintaining the aortic column of blood at a roughly constant pressure. In ventricular sistole the blood pressure in the left ventricle rises rapidly and when it is higher than the aortic pressure the aortic valve opens. At top left some papillary muscles of the right atrium are visible. Magnification: x93 at 6x7cm size.
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