Common Misconceptions

Misconception: "Arteries always carry oxygenated blood and veins always carry deoxygenated blood."

Reality: Arteries carry blood away from the heart and veins carry blood to the heart — this is the correct definition. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs, and the pulmonary veins carry oxygenated blood from the lungs back to the left atrium. This is the most commonly tested exception in exams.

Misconception: "The heart is on the left side of the chest."

Reality: The heart is positioned roughly in the centre of the chest, behind the sternum (breastbone), between the lungs. It is tilted very slightly to the left, which is why the heartbeat can be felt more strongly on the left side. In diagrams of the heart, left and right are always shown from the patient's perspective, not the viewer's — so the right side of the heart appears on the left of the diagram.

Misconception: "Deoxygenated blood is blue in the body."

Reality: Blood is always red. Oxygenated blood (carrying oxygen bound to haemoglobin) is bright red. Deoxygenated blood is a darker, dusky red — not blue. The blue colour used in diagrams is just a convention to distinguish the two types visually. Veins appear bluish-green through the skin because of how light penetrates tissue, not because the blood itself is blue.