What is the name of the depression in the septum of the atria that closes after birth?

The depression in the septum of the atria that closes after birth is known as the foramen ovale. During fetal development, this opening allows blood to bypass the non-functioning fetal lungs, enabling oxygenated blood from the placenta to flow directly from the right atrium to the left atrium. After birth, the significant increase in blood flow to the lungs and the resultant changes in pressure lead to the closure of this opening, which becomes the fossa ovalis. This transition is crucial for the normal adaptation of the cardiovascular system to life outside of the womb.

Understanding this concept is important, as it plays a critical role in the fetal circulation and the adaptation to neonatal circulation post-birth. Other terms like septal defect refer to abnormal openings, or atrial septum which is simply the wall separating the atria, but they do not specifically describe the closure of the foramen ovale after delivery.