Heart valve and strings, coloured scanning electron micrograph (SEM). This is the tricuspid valve, seen from the right ventricle of the heart. The heart strings (thread-like structures) are known as the chordae tendineae, and connect the valves to the papilliary muscle used to control their opening and closing. The tricuspid valve lies between the right atrium and the right ventricle, helping to control the flow of blood between these two chambers of the heart.