Questions: Cardiovascular System Overview

Question 1

The pulmonary artery carries blood from the right ventricle to the lungs. What type of blood does it carry?

• A. Oxygenated blood, because arteries always carry oxygenated blood
• B. Deoxygenated blood, because it is traveling to the lungs to pick up oxygen
• C. A mixture of oxygenated and deoxygenated blood
• D. Blood with no oxygen at all

Answer: (B)

The pulmonary artery carries deoxygenated blood from the right ventricle to the pulmonary capillaries, where CO₂ is offloaded and O₂ is picked up. The rule 'arteries carry oxygenated blood' applies to the systemic circuit but breaks down for the pulmonary circuit. Arteries are defined by direction of flow (away from the heart), not by oxygen content.

Question 2

Arteries typically carry oxygenated blood and veins usually carry deoxygenated blood.

• T. True
• F. False

Answer: False

This is the most common misconception about the cardiovascular system. In the pulmonary circuit, the pulmonary artery carries deoxygenated blood to the lungs, and the pulmonary veins return oxygenated blood to the heart. Arteries and veins are defined by direction relative to the heart (away vs. toward), not by oxygen content.

Question 3

Why does the body need a double circuit (pulmonary + systemic) rather than a single loop where blood passes through the lungs and body tissues in one continuous circuit?

Model answer: A double circuit allows the heart to repressurize blood after it passes through the low-resistance pulmonary capillaries before sending it through the high-resistance systemic circuit. Without re-pumping, pressure would be too low to perfuse body tissues effectively. It also allows the two circuits to operate at different pressures appropriate to their functions.

This tests functional understanding rather than just anatomical knowledge. The pulmonary circuit operates at low pressure to protect the delicate lung capillaries; the systemic circuit needs higher pressure to perfuse distant tissues. A single-circuit heart (as in fish) cannot maintain adequate pressure in both simultaneously.