Which vessels lack elastic tissue?

Which vessels lack elastic tissue?

• A. Arterioles and capillaries
• B. Arteries and arterioles
• C. Veins and venules
• D. Capillaries and venules

Answer: (A)

Elastic tissue is prominent in the walls of large arteries to allow stretch and recoil with each heartbeat. As vessels get smaller, that elastic component drops away. Arterioles and capillaries fit this pattern: arterioles have walls dominated by smooth muscle with little to no elastic fibers, and capillaries consist of a single endothelial layer with no tunica media or elastic tissue. So these vessels lack elastic tissue. Other vessels contain some elastic fibers, especially arteries, so they don’t fit as lacking elastic tissue.

Elastic tissue is prominent in the walls of large arteries to allow stretch and recoil with each heartbeat. As vessels get smaller, that elastic component drops away. Arterioles and capillaries fit this pattern: arterioles have walls dominated by smooth muscle with little to no elastic fibers, and capillaries consist of a single endothelial layer with no tunica media or elastic tissue. So these vessels lack elastic tissue. Other vessels contain some elastic fibers, especially arteries, so they don’t fit as lacking elastic tissue.