Smooth part of left atrium

The smooth part of the left atrium refers to the main body of the chamber, excluding the left atrial appendage and the pectinate muscles. This region is primarily formed embryologically by the incorporation of the pulmonary veins into the atrial wall, resulting in a smooth-walled posterior and superior surface. The smooth part receives the four pulmonary veins at its posterosuperior aspect, forming a prominent atrial dome. The anterior portion of the left atrium, surrounding the mitral valve orifice, is known as the vestibule of left atrioventricular valve.