PATHOLOGY

Detailed explanation-1: -The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of the heart.

Detailed explanation-2: -The sinuatrial node, which is responsible for regulating the automaticity of the myocardium, is located in the posterior wall of the right atrium. More specifically, it is inferolateral to the opening of the superior vena cava, along the superior part of the crista terminalis.

Detailed explanation-3: -The upper two chambers are the atria, and the lower two are the ventricles (Figure A). The chambers are separated by a wall of tissue called the septum. Blood is pumped through the chambers, aided by four heart valves.