PATHOLOGY

Detailed explanation-1: -Oxygen-rich blood flows from the lungs back into the left atrium (LA), or the left upper chamber of the heart, through four pulmonary veins. Oxygen-rich blood then flows through the mitral valve (MV) into the left ventricle (LV), or the left lower chamber.

Detailed explanation-2: -There are 4 total pulmonary veins-with 2 pulmonary veins coming from each lung, left and right-that empty into the left atrium of the heart. Two pulmonary veins emerge from the hilus of each lung, and each pulmonary vein receives blood from 3-4 bronchial veins apiece before draining into the left atrium.