Acland's Video Atlas of Human Anatomy

To look at the inside of the right atrium, we'll remove this part of its wall. Here's the opening of the superior vena cava above, and of the inferior vena cava below. Here's the opening of the coronary sinus. This is the part of the atrial wall that's shared with the left atrium, the inter-atrial septum. This thin oval patch in the septum is the fossa ovale: the remnant of the foramen ovale that connected the two atria in intrauterine life.