Inter Articulam Septum

The interatrial septum is the thin, muscular wall separating the right and left atria (the upper chambers) of the heart. During fetal development, it features the foramen ovale, a flap-like opening that allows blood to bypass the lungs and flow directly from the right to the left atrium. After birth, the foramen ovale closes and fuses with the septum, forming the fossa ovalis, a central depression in the adult interatrial septum. In adults, the septum prevents blood mixing between the atria, maintaining separate oxygenated and deoxygenated blood.