Left fibrous ring

The left fibrous ring of the heart is a component of the cardiac fibrous skeleton that forms the annulus of the mitral valve,.

It provides structural support and anchoring the mitral valve leaflets between the left atrium and left ventricle. The left fibrous ring is not a discrete, perfectly circular ring but rather a band-like fibrous tissue that is part of a larger connective tissue system, which includes the left and right fibrous trigones and is directly connected to the membranous septum and the aortic root attachment to the left ventricular muscle. The majority of the mitral annulus is fibrous, distinguishing it from the tricuspid annulus, which is only partially fibrous.

The fibrous skeleton, including the left fibrous ring, serves to electrically insulate the atria from the ventricles (except at the atrioventricular node), maintain the integrity of the valvular orifices, and provide attachment points for the cardiac valves and myocardium.