A. Chordae tendinae: The structure pointed to by the line is the chordae tendineae. The chordae tendineae are strong, fibrous collagen cords that connect the atrioventricular valve leaflets (mitral and tricuspid valves) to the papillary muscles within the ventricles. They prevent valve prolapse during ventricular systole. When the ventricles contract, papillary muscles also contract, maintaining tension on the chordae tendineae to keep the valves closed and prevent backflow into the atria. B. Papillary Muscles: Papillary muscles are cone-shaped projections from the ventricular walls that anchor chordae tendineae. During ventricular contraction, they prevent valve prolapse by maintaining tension on valve leaflets, ensuring unidirectional blood flow C. Septal leaflet: The septal leaflet is part of the tricuspid valve attached to the interventricular septum. Chordae tendineae connect it to papillary muscles, stabilizing the valve during systole and preventing backflow into the right atrium. D: Pulmonary vein: Pulmonary veins are vessels transporting oxygenated blood from the lungs to the left atrium. They are not directly connected to chordae tendineae but are adjacent to atrial structures influencing left atrial filling and valve dynamics.