Named Blood Vessels in the Circulatory System

Explained

The named vessels, and how the names give away the answer

This looks like a long list to memorise, and it is not. Almost every vessel is named by joining an organ to a vessel type, so knowing the pattern lets you work out names you have never seen written down.

Renal means kidney. Hepatic means liver. Pulmonary means lung. Coronary means the heart's own muscle. Add artery or vein to any of those and you have the vessel.

Then apply the two rules that never change. An artery carries blood away from the heart. A vein carries blood towards the heart. So a renal artery carries blood from the heart to the kidney, and a renal vein carries it from the kidney back to the heart, without anything further needing to be learned.

The vessels serving the heart and lungs

The vena cava carries deoxygenated blood from the body into the right atrium.

The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.

The pulmonary vein carries oxygenated blood from the lungs to the left atrium.

The aorta carries oxygenated blood from the left ventricle to the body.

The coronary arteries branch off the aorta almost immediately and supply the heart muscle itself. The heart cannot absorb oxygen from the blood passing through its chambers, so it needs its own supply, and a blockage in a coronary artery is what causes a heart attack.

The pulmonary pair are the exception to the usual association of arteries with oxygen. Artery means away from the heart, and that is all it means. Because the pulmonary artery is heading to the lungs to collect oxygen, it must be carrying blood that has none.

The vessels serving the liver and kidneys

The renal arteries carry oxygenated blood from the aorta to the kidneys. The renal veins carry blood, now with the urea removed, back to the vena cava.

The hepatic artery carries oxygenated blood from the aorta to the liver. The hepatic vein carries blood from the liver back to the vena cava.

The hepatic portal vein is the one worth understanding rather than learning. It carries blood from the small intestine to the liver.

Why the hepatic portal vein is unusual

Almost all blood returns to the heart after leaving an organ. This one does not. It leaves the small intestine and goes straight to a second organ before the heart sees it at all.

The reason is that blood leaving the intestine has just absorbed everything from a meal, so it is loaded with glucose and amino acids in whatever quantities the meal happened to contain. Sending that directly round the body would swing the blood composition wildly after every meal.

The liver takes it first and regulates it, storing excess glucose as glycogen and deaminating surplus amino acids. What reaches the rest of the body is controlled rather than whatever was eaten.

It is also called a vein despite carrying blood towards an organ rather than the heart, which is worth noticing so the name does not look like a mistake. Portal describes a vessel running between two capillary beds, and this is the only one in the specification.

Tracing a route

Questions often ask you to describe the path from one place to another, and the reliable method is to go through the heart every time rather than looking for a shortcut.

From the small intestine to the kidney, for instance: small intestine, hepatic portal vein, liver, hepatic vein, vena cava, right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta, renal artery, kidney.

That looks long, and writing it out is what earns the marks. Blood cannot travel from one organ to another without returning to the heart, except in that single hepatic portal case.

Why the circulation is called double

Blood passes through the heart twice in one complete circuit of the body.

Once through the right side and the lungs, which is the pulmonary circuit, and once through the left side and the body, which is the systemic circuit.

The advantage is pressure. Blood loses pressure passing through the capillaries of the lungs, and returning it to the heart lets it be pumped again at full pressure to the body. A single circulation would deliver blood to the body at whatever pressure was left after the lungs, and it would circulate more slowly.