The interatrial septum (Fig. 1) is the structure that divides the primary atrium into the right and left atrial chambers. Starting the fifth week of gestation, the septum primum begins to develop, growing toward the endocardial cushions.

What forms the interatrial septum?

Embryology. The atrial septum forms as a result of fusion of several structures. The muscular upper aspect of the atrial septum (septum secundum) is formed by invagination of the roof of the embryologic atrium. Its inferior free margin is marked by the limbus.

What is the function of the interatrial and interatrial septum?

cardiovascular system. …a partition known as the interatrial septum; the lower chambers, the ventricles, are separated by the interventricular septum. The atria receive blood from various parts of the body and pass it into the ventricles. The ventricles, in turn, pump blood to the lungs and to the remainder of the body ...