Although the axiom form follows function was originally coined by Louis Sullivan in 1896 to describe the functionality of tall buildings, it is also used in medicine but with less mathematic formulation. For instance, the anatomy of the tricuspid valve (TV) is highly variable and yet it functions perfectly well as long as the right ventricle is normal. However, because of the high variability of this anatomically complex valve, functional tricuspid regurgitation (TR) is a perplexing lesion. The development of the atrioventricular valves is one of the most complex events of cardiac morphogenesis. Lamers and colleagues summarized the morphogenesis of the TV in the following sentences. ‘‘Concurrent with the development of the right atrioventricular connection, a myocardial ridge forms at the boundary between the atrioventricular canal and the embryonic right ventricle. It grows to become a myocardial gully that funnels atrial blood beneath the lesser curvature of the initial heart tube toward the middle of the right ventricle. Fenestrations in the floor of the gully create an additional inferior opening in the funnel, transforming its initial anterior rim into the septomarginal trabeculation. The septum formed by the fusion of the endocardial ridges of the outflow tract becomes myocardialized in its inferior portion to form, in part, the outlet septum and, in part, the supraventricular crest. The smooth atrial surface of the tricuspid valvar leaflets develops from endocardial cushion tissue. The leaflets become freely movable, however, only after delamination of the tension apparatus within the myocardium. The inferior and septal leaflets derive from the gully and the ventricular septum, their delamination being a single, continuous process. The anterosuperior leaflet forms by delamination from the developing supraventricular crest.’’ Given the complexity of its embryologic development, it is no wonder that the final anatomy of the TV is highly variable. In classic anatomic studies, the TV is described as having 3 leaflets: the anterior, posterior, and septal. When viewed from its atrial side, the 3 leaflets are attached to the interventricular septum and right ventricular wall and the valve orifice is roughly triangular. Thus, the TV has 3 commissures: anteroseptal, anteroposterior, and posteroseptal. The base of the septal leaflet is attached largely to the interventricular septum, and a small part is attached to the posterior ventricular wall without a distinct annulus. The free margin of the septal leaflet is anchored mostly by chordae tendineae originating directly from the interventricular septum, and only a small part of this leaflet is anchored by chordae from the posterior papillary muscle or directly from the posterior wall trabeculae. The base of the anterior and posterior leaflets is attached to the right ventricular wall through a fibrous annulus. The free margins of the anterior and posterior leaflets are an-