Final answer:
A septum is a wall that divides the heart into chambers, with the main ones being the interatrial and interventricular septa.
Step-by-step explanation:
A septum refers to a wall or partition that divides the heart into chambers. These septa are an integral part of the heart's structure, ensuring that blood flows in the correct direction through the various chambers of the heart. The main septa are the interatrial septum, which separates the two atria, and the interventricular septum that divides the two ventricles.
In an adult heart, the interatrial septum features the fossa ovalis, a depression that is the remnant of the fetal foramen ovale, which allowed blood to bypass the pulmonary circuit in a fetus. Seconds after birth, the septum primum closes this opening, sealing off the foramen ovale and establishing the typical cardiac circulation. The cardiac chambers and valves, formed by these septa and muscular tissues like the myocardium, are vital in maintaining efficient cardiac function and circulation.