Oblique vein of left atrium

In carnivores, the oblique vein of the left atrium (Vena obliqua atrii sinistri: Marshall's vein in humans) is a small, often delicate and sometimes variable vessel that drains the caudal wall of the left atrium. It runs obliquely across the posterior surface of the left atrium from dorsal to ventral, typically converging into the coronary sinus near its origin. This vein represents a remnant of the embryonic left common cardinal vein (duct of Cuvier) and contributes minimally to overall cardiac venous return compared with larger vessels such as the great cardiac vein. Despite its small size, it is anatomically significant due to its consistent relationship with the coronary sinus and left atrial wall.