This is how our body reacts when we get nervous I Macro view

There are a lot of tiny lines on fingertips and palm called epidermal ridges. The ducts of sweat glands is open on tops of the ridges causing prints that are left on a surface.
when we get nervous in this situation our body release sweat mostly from the palms, this video will take you in a macro zoom view of a palm showing how our palm release sweat from pores of the fingerprints.