How Do Pulmonary Arteries and Veins Differ From Others

The difference between pulmonary and systemic vessels is the **type of blood they carry (oxygenated vs. deoxygenated)**. This is the major exception to the general rule of circulation.

The "rule" for all vessels is based on the direction of flow relative to the heart:

• Arteries carry blood AWAY from the heart.
• Veins carry blood TOWARD the heart.

Here is the comparison:

• Systemic Arteries (e.g., Aorta): Carry oxygenated bloodaway from the heart (left ventricle) to the rest of the body.
• Systemic Veins (e.g., Vena Cava): Carry deoxygenated bloodtoward the heart (right atrium) from the body.

The pulmonary circuit is the opposite in terms of oxygen content:

• Pulmonary Artery: The only artery that carries deoxygenated blood. It carries this blood away from the heart's right ventricle and to the lungs to get oxygen.
• Pulmonary Veins: The only veins that carry oxygenated blood. They carry this freshly oxygenated blood from the lungs toward the heart's left atrium to be pumped out to the body.