atrial septum (anatomy)

Last reviewed 01/2018

The interatrial septum of the heart is the wall of the dividing right and left atria; due to its obliquity, right atrium mainly lies anterior to left atrium . Its development is considered in the submenu.

In the right atrium, it forms the posterior wall in the region superior to the coronary sinus. Within this region are the:

• fossa ovalis
• limbus fossae ovalis
• torus aorticus
• tendon of Todaro
• triangular area and underlying septal portion of atrioventricular node

In the left atrium, the septum lies obliquely, running posteriorly from right to left. Within this region may be an oval depression indicative of the ostium secundum of development.

The interatrial septum is the site of persistent foramen ovale.