Final answer:
Deoxygenated blood is returned to the right side of the heart via the superior and inferior vena cava, enters the right atrium, passes through the tricuspid valve, and fills the right ventricle.
Step-by-step explanation:
After being used by the major organs of the body, deoxygenated blood is transported back to the right side of the heart by two large veins known as the superior and inferior vena cava, and enters the right atrium, quickly passing by the open tricuspid valve, where blood then enters and fills the right ventricle chamber.
The superior vena cava drains blood from the upper part of the body, while the inferior vena cava collects blood from the lower parts, including the legs. Blood in the right atrium then moves through the tricuspid valve to the right ventricle.
From there, the deoxygenated blood is pumped to the lungs for oxygenation in the pulmonary circuit. This process is crucial as it ensures that the body has a continuous supply of oxygenated blood, which is essential for maintaining life and function.