Septum primum

Definition

The septum primum is a thin, crescent-shaped membrane in the developing heart of a fetus that initially forms the partial separation between the right and left atria. It plays a critical role in the development of the heart's structure, eventually contributing to the formation of the atrial septum, which separates these two chambers completely after birth.

Related terms

Atrial Septum: The final structure formed by the fusion of the septum primum with other cardiac components that fully separates the left and right atria.

Foramen Ovale: A fetal opening in the interatrial septum allowing blood to bypass pulmonary circulation by flowing directly from the right to left atrium, which closes soon after birth.

Endocardial Cushions: Structures that contribute to heart septation and valve formation, playing a critical role in dividing the heart into four chambers