The easiest way to imagine how cylinders have different surface area for a given volume, is imagine how closely a shape matches a sphere, it should have a lower surface area.

Imagine a soda can with the width of one water molecule. The cross section of that can would be on the order of four aluminum atoms for that hair thin can. Then imagine a can that’s nearly a cube or a sphere and how all the liquid can be hiding behind other liquid atoms: hence fewer can atoms per liquid volume.

Blood vessels have high surface area. A pint of blood has low.