How Would You Explain The Route Of Pulmonary Circulation?

The unoxygenated blood returns to the heart via our superior and inferior vena cava to the right atrium of the heart passing the coronary sinuses. Once the blood enters the atrium, it flows to the right ventricle of the heart passing the tricuspid valve, then it flows to the pulmonary trunk passing the pulmonary or semilunar valve then it continues to flow into the lungs, where the gas exchange occurs. The unoxygenated blood is being oxygenated and continues to flow to the left atrium of the heart then past the bicuspid valve then enters the left ventricle then blood is being ejected to the systemic circulation.

After systemic circulation is completed and the blood is put into the right atrium by the inferior and superior vena cava, this blood then passes into the right ventricle which contracts and pumps it into the pulmonary artery.  This divides to carry blood to the right and left lungs.  The lungs offer very little resistance to the blood in the vessels flowing through them.  In the lungs each artery breaks up into numerous smaller arteries, then into arterioles and finally into pulmonary capillaries which surround the alveoli in the lung tissue where the blood takes up oxygen and gives off carbon dioxide.

The pulmonary capillaries then unite until veins are formed and the blood is returned to the heart by four pulmonary veins which empty into the left atrium.  The blood then passes into the left ventricle which contracts and pumps it into the aorta to begin the systemic circulation again.  

Pulmonary edema accompanies failure of the left side of the heart.  Tissue fluid collects into the lungs, whose function is impaired.  Pulmonary edema can also occur if a patient who is ill is over hydrated; his/ her lungs become water logged and it is possible that he/ she may drown in his/ her own pulmonary edema.