The<unk> , or heart strings, are cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart.
When the right ventricle of the heart contracts, the blood pressure pushes the tricuspid valve which closes and prevents a backflow of blood into the right atrium. The<unk>  prevents the flaps from being everted into the right atrium. Similarly, these cord-like tendons hold in position other flaps like the bicuspid or mitral valve.<unk>  are approximately 80% collagen, while the remaining 20% is made up of elastin and endothelial cells.
Chordae tendineae
Tunica externa 
Tunica intima
Fibrous pericardium
Interatrial septum
Transverse intermuscular septum
Anterior crural intermuscular septum
Interventricular septum