How do arterial and venous blood differ?

• A. Arterial blood carries oxygen to tissues; venous blood returns deoxygenated blood to the heart
• B. Arterial blood carries deoxygenated blood to tissues
• C. Arterial blood is thicker than venous blood
• D. Arterial blood is found in veins

Answer: (A)

Arterial and venous blood differ mainly in oxygen content and the direction of flow relative to the heart. In systemic circulation, arterial blood is oxygen-rich and travels away from the heart to supply tissues with oxygen. Venous blood, after delivering oxygen and collecting waste products, returns to the heart and is deoxygenated. This opposite flow pattern is what sets them apart and explains why arterial blood is described as carrying oxygen to tissues while venous blood returns deoxygenated blood to the heart.

Note that on the pulmonary side, the pattern reverses: arteries carry less-oxygenated blood to the lungs and veins bring oxygenated blood back to the heart. The idea that arterial blood is thicker or that arterial blood would be found in veins isn’t accurate for normal anatomy; the key distinction is oxygen content and flow direction.