When blood vessel length increases, what happens to the surface area?

When blood vessel length increases, what happens to the surface area?

• A. It decreases
• B. It remains unchanged
• C. It increases
• D. It doubles immediately

Answer: (C)

Think of a blood vessel as a cylinder. Its surface area is mainly the side area, which equals 2π r L (radius times length, times a constant). If the length increases while the radius stays the same, that side area grows in direct proportion to the length. So the total surface area increases as the vessel gets longer. It’s not an instantaneous doubling; the change is linear with how much you lengthen the vessel. The other options don’t fit because a longer cylinder simply has more wall surface, not less or unchanged, and it doesn’t jump to a doubled value unless length changes by a specific factor.

Think of a blood vessel as a cylinder. Its surface area is mainly the side area, which equals 2π r L (radius times length, times a constant). If the length increases while the radius stays the same, that side area grows in direct proportion to the length. So the total surface area increases as the vessel gets longer. It’s not an instantaneous doubling; the change is linear with how much you lengthen the vessel. The other options don’t fit because a longer cylinder simply has more wall surface, not less or unchanged, and it doesn’t jump to a doubled value unless length changes by a specific factor.