Correct Option
The correct option isArteries have thick elastic walls, whereas veins have thin walls.
Explanation
The circulatory system comprises blood vessels that transport blood throughout the body. The structural differences between arteries and veins are dictated by their specific functions regarding blood pressure management and the direction of blood flow relative to the heart.
Option Analysis
- Arteries possess valves, whereas veins do not. is Incorrect: Arteries do not possess valves because blood flows through them under high pressure, which naturally prevents backflow. Veins possess valves to prevent the backflow of blood, as they carry blood under much lower pressure against gravity.
- Arteries carry blood towards the heart, whereas veins carry it away. is Incorrect: The definition of these vessels is based on flow direction. Arteries carry blood away from the heart to various body parts. Veins carry blood towards the heart from various body parts.
- Arteries have thick elastic walls, whereas veins have thin walls. is Correct: Arteries have thick, elastic, and muscular walls to withstand the high pressure of blood pumped directly by the heart. In contrast, veins have thinner walls and a wider lumen because the blood flowing through them is under significantly lower pressure.
- Arteries always carry deoxygenated blood, whereas veins always carry oxygenated blood. is Incorrect: While systemic arteries generally carry oxygenated blood and systemic veins carry deoxygenated blood, there are crucial exceptions. The Pulmonary Artery carries deoxygenated blood from the heart to the lungs, and the Pulmonary Vein carries oxygenated blood from the lungs to the heart. Therefore, the use of "always" makes this statement factually wrong.
Key Takeaway: Arteries are thick-walled, high-pressure vessels that transport blood away from the heart, whereas veins are thin-walled, valved vessels that return blood to the heart.