Which blood vessels lack elastic tissue?

• A. Capillaries
• B. Arteries
• C. Arterioles
• D. Veins

Answer: (A)

Verified step by step guidance

1. Understand the structure of blood vessels: Blood vessels are composed of three layers - the tunica intima, tunica media, and tunica externa. The presence of elastic tissue varies among different types of blood vessels.
2. Identify the role of elastic tissue: Elastic tissue in blood vessels allows them to stretch and recoil, which is crucial for maintaining blood pressure and accommodating the surge of blood from the heart.
3. Examine the structure of capillaries: Capillaries are the smallest blood vessels and are primarily composed of a single layer of endothelial cells. They lack the tunica media and tunica externa, and therefore, do not contain elastic tissue.
4. Compare with other blood vessels: Arteries and arterioles have a significant amount of elastic tissue in their walls, especially in the tunica media, to withstand and regulate the high pressure of blood pumped from the heart. Veins have less elastic tissue compared to arteries but still contain some to help return blood to the heart.
5. Conclude which vessels lack elastic tissue: Based on the structural differences, capillaries are the blood vessels that lack elastic tissue, as they are designed for the exchange of nutrients and gases rather than withstanding high pressure.