Which of the following structures carry oxygen-poor blood?

• A. Aorta
• B. Pulmonary veins
• C. Pulmonary arteries
• D. Left atrium

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the function of each structure mentioned in the problem. The aorta carries oxygen-rich blood from the left ventricle to the rest of the body. Pulmonary veins carry oxygen-rich blood from the lungs to the left atrium. Pulmonary arteries carry oxygen-poor blood from the right ventricle to the lungs for oxygenation. The left atrium receives oxygen-rich blood from the pulmonary veins.
2. Step 2: Recall the distinction between oxygen-rich and oxygen-poor blood. Oxygen-poor blood is blood that has a lower concentration of oxygen and a higher concentration of carbon dioxide, typically carried by veins (except pulmonary veins) and certain arteries like pulmonary arteries.
3. Step 3: Focus on the pulmonary arteries. These are unique because they are the only arteries in the body that carry oxygen-poor blood. They transport blood from the right ventricle to the lungs for gas exchange.
4. Step 4: Eliminate the other options based on their roles. The aorta and pulmonary veins carry oxygen-rich blood, and the left atrium receives oxygen-rich blood from the pulmonary veins. None of these structures carry oxygen-poor blood.
5. Step 5: Conclude that the pulmonary arteries are the correct answer because they are the only structures listed that carry oxygen-poor blood to the lungs for oxygenation.