Arteries Have Thickest Walls Due to High Pressure

Steps:

• Identify blood vessel types: arteries, veins, capillaries, and smaller vessels like arterioles.
• Recall arteries carry oxygenated blood from the heart under high pressure.
• Note arteries require thick walls of muscle and elastic tissue to withstand and regulate this pressure.
• Compare: veins return low-pressure blood with thinner walls; capillaries are thinnest for diffusion.

Why A is correct:

• Arteries possess the thickest walls, defined by layers of smooth muscle and elastin to endure systolic pressure up to 120 mmHg without rupturing.

Why the others are wrong:

• B (vein): Thinner walls with valves suffice for low-pressure return flow.
• C (capillary): Single endothelial layer enables nutrient exchange, not structural strength.
• D (arteriole): Narrower and less muscular than large arteries, aiding local blood distribution.

Final answer: A