Blood vessels of the heart

Four main vessels connect the heart to the body and the lungs. To identify a vessel, follow its connection and determine whether blood enters or leaves the heart through it.

Vessels entering the heart

• The vena cava brings blood from the body into the right atrium.
• The pulmonary vein brings blood from the lungs into the left atrium.

Vessels leaving the heart

• The aorta carries blood from the left ventricle to the body.
• The pulmonary artery carries blood from the right ventricle to the lungs.

Identifying the vessels on a heart diagram

Trace each vessel to the chamber it connects to: the vena cava and pulmonary vein enter atria, while the aorta and pulmonary artery leave ventricles. The heart’s right and left are the person’s right and left; on a diagram viewed from the front, the right side of the heart usually appears on the left of the page.

A diagram may show more than one vena cava or pulmonary vein. Follow each vessel’s connection to the heart and its route to or from the body or lungs.

Blood vessels of the lungs

The lungs are connected to the heart by blood vessels that carry blood in opposite directions:

• The pulmonary artery carries blood from the heart to the lungs. It arrives at the lungs.
• The pulmonary vein carries blood from the lungs back to the heart. It leaves the lungs.

When identifying these vessels in a diagram, follow the direction of blood flow in relation to the lungs. A vessel carrying blood towards the lungs is the pulmonary artery; one carrying blood away from the lungs towards the heart is the pulmonary vein.

Blood vessels of the kidney

Blood reaches the kidney through one main vessel and leaves through another. These vessels are named according to the direction in which they carry blood:

• The renal artery carries blood to the kidney from the arterial system.
• The renal vein carries blood away from the kidney to the venous system.

In a diagram or image, locate the vessels connected to the kidney. The vessel entering from the arterial system is the renal artery; the vessel leaving to join the venous system is the renal vein. If arrows show blood flow, use their direction to distinguish the blood input from the blood output.

Blood vessels of the liver

Three main blood vessels connect the liver to the circulation. Two carry blood into the liver, while one carries blood away from it.

• The hepatic artery carries blood to the liver from the arterial circulation.
• The hepatic portal vein carries blood to the liver from the digestive organs.
• The hepatic vein carries blood away from the liver.

In a diagram, identify each vessel by the direction in which it carries blood relative to the liver. The hepatic artery and hepatic portal vein enter the liver; the hepatic vein leaves it. Despite its name, the hepatic portal vein carries blood towards the liver, not away from it.