In a normal heart, all deoxygenated blood collects and returns to the heart through the vena cava. The vena cava is composed of a superior part (through which blood from above the heart returns) and an inferior part (through which blood from below the heart returns). The blood from these two branches of the vena cava converges and the deoxygenated blood flows into the right atrium. From there, again, normally, the blood flows into the right ventricle, passing through the tricuspid valve which regulates the flow and prevents back flow. The right ventricle pumps the deoxygenated blood through the pulmonary artery to the lungs to get reoxygenated. (Even though the pulmonary artery carries deoxygenated blood, it is called an artery because it carries blood away from the heart.) After reoxygenation in the lungs, the blood is returned to the left side of the heart where the left atrium and then ventricle pump it out to supply the body.
Heart function and circulation medical expert witness specialties include cardiology, interventional cardiology, pathology, heart failure cardiology, internal medicine, pediatrics, family medicine, hospitalist medicine, and pediatric hospitalist medicine.