Final answer:
The right atrium is the chamber of the heart that receives deoxygenated blood from the cranial vena cava, caudal vena cava, and the coronary sinus, which are collectively responsible for returning systemic circulation to the heart.
Step-by-step explanation:
The chamber of the heart that receives deoxygenated blood from the cranial vena cava, caudal vena cava, and the coronary sinus is the right atrium. The right atrium serves as the receiving chamber for systemic circulation, with blood from above the diaphragm arriving via the superior vena cava and blood from below the diaphragm arriving through the inferior vena cava. Blood from the heart's own muscle tissue, which arrives through the coronary sinus, also empties into the right atrium. This oxygen-poor blood from the body is then transferred to the right ventricle, which pumps it to the lungs for oxygenation.