What is the fibrous tissue called that separates the atrium and ventricle of the same side in the human heart?

Step-by-step solution

Our heart has four chambers, two relatively small upper chambers called atria and two larger lower chambers called ventricles. A thin, muscular wall called the interatrial septum separates the right and the left atria, whereas a thick-walled, the inter-ventricular septum, separates the left and the right ventricles . The atrium and the ventricle of the same side are also separated by a thick fibrous tissue called the atrio-ventricular septum . However, each of these septa are provided with an opening through which