Septal Papillary Muscle
The papillary muscles are specialised structures in the ventricles which attach to the atrioventricular valves (tricuspid and mitral) via string-like extensions known as chordeae tendineae. They contract to prevent the atrioventricular valves from inverting and allowing blood to flow backwards into the atria.
In the ventricles there are muscular ridges known as trabeculae carneae. Papillary muscles are specialised trabeculae carneae which are attached at one end to the ventricle wall, and at the other to the chordae tendineae.
There are three papillary muscles in the right ventricle:
These attach to the tricuspid valve.
There are two papillary muscles in the left ventricle:
These attach to the mitral valve.