Overview of Systemic and Pulmonary Circulation

The right ventricle pumps deoxygenated blood into the pulmonary trunk, which divides into the left and right pulmonary arteries. These arteries deliver blood to the lungs for oxygenation. This is the first step in pulmonary circulation, where blood exchanges carbon dioxide for oxygen before returning to the heart via pulmonary veins.

Oxygenated blood leaves the lungs via the pulmonary veins and enters the left atrium. From there, blood moves to the left ventricle, which marks the beginning of systemic circulation. This pathway completes the pulmonary circuit and prepares oxygenated blood for distribution throughout the body.

Blood exits the left ventricle into the ascending aorta, passes through the aortic arch, and continues through the descending aorta. These major vessels distribute oxygenated blood to all tissues and organs throughout the body during systemic circulation. The aorta is the primary vessel delivering blood to peripheral tissues.

The superior vena cava carries blood from regions above the diaphragm, the inferior vena cava from regions below the diaphragm, and the coronary sinus from the myocardium. These three systemic veins collect deoxygenated blood and return it to the right atrium to restart pulmonary circulation.

As blood circulates through systemic tissues, it exchanges oxygen and nutrients with surrounding cells and picks up carbon dioxide and metabolic waste. This gas and nutrient exchange transforms oxygenated blood into deoxygenated blood, which then returns to the heart via systemic veins for reoxygenation.

Pulmonary circulation oxygenates blood in the lungs, then systemic circulation delivers that oxygenated blood throughout the body. After tissues extract oxygen and nutrients, deoxygenated blood returns to the right atrium, restarting the pulmonary circuit. This sequential cycle maintains continuous blood flow and gas exchange.

The right ventricle contracts to pump deoxygenated blood to the lungs via the pulmonary trunk, while the left ventricle contracts to distribute oxygenated blood throughout the body via the aorta. This coordinated pumping action between the chambers maintains continuous circulation between the heart, lungs, and tissues.