Common Misconceptions

Misconception: "White blood cells eat germs."

Reality: The correct term is phagocytosis — phagocytes extend their membrane around the pathogen and engulf it, forming an internal vesicle. The pathogen is then digested by enzymes. This is a precise biological process, not casual eating.

Misconception: "Platelets are cells."

Reality: Platelets are cell fragments, not whole cells. They are produced when large cells in bone marrow (megakaryocytes) break apart. Platelets have no nucleus and cannot divide or carry out protein synthesis.

Misconception: "Blood is blue when it is deoxygenated, because veins look blue."

Reality: Blood is never blue. Deoxygenated blood is dark red, not blue. Veins appear blue through the skin because different wavelengths of light penetrate tissue to different depths — blue light reflects back more readily than red light. If you have ever had a blood test, the blood drawn from a vein is visibly dark red.

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

Reality: Arteries carry blood away from the heart; veins carry blood towards the heart. The pulmonary artery carries deoxygenated blood to the lungs, and the pulmonary vein carries oxygenated blood back to the heart — the opposite of the general rule.