ZEPHYR / SCIENCE PHOTO LIBRARY ZEPHYR / SCIENCE PHOTO LIBRARY
Heartbeat. Coloured magnetic resonance imaging (MRI) scans of transverse (top) and vertical (bottom) sections through a 45-year-old's chest showing a healthy heart. The two ventricles (lower chambers, orange) of the heart are shown. The width of the left ventricle has been measured. At left the heart is in ventricular diastole, a period of relaxation. As the muscles relax the pressure in the left ventricle decreases and oxygenated blood enters it from the left atrium (upper chamber). At right the heart is in systole. The left ventricle is contracting, pushing the blood into the aorta, the body's main artery.
Model release not required. Property release not required.