Final answer:
The strong strands of connective tissue that attach each flap of the heart's valve to the papillary muscles are known as the chordae tendineae, or heart strings. These structures, mainly comprised of collagen, prevent the inversion of the valves during the heart's contractions and backflow of blood.
Step-by-step explanation:
Each flap of the valve in the heart is attached to strong strands of connective tissue, the chordae tendineae, which are sometimes referred to as "heart strings." These chordae tendineae consist mainly of collagenous fibers, along with some elastic fibers and endothelium. They serve the critical function of connecting the valve flaps to the papillary muscles, which arise from the inferior ventricular surface within the heart's ventricles. Particularly, the right ventricle features three papillary muscles known as the anterior, posterior, and septal muscles, that mirror the three sections of the tricuspid valve. During ventricular contraction, the papillary muscles contract, exerting tension on the chordae tendineae, which prevents the valvular flaps from inverting into the atria and thus avoids the backflow of blood.