A biology teacher might define “peristalsis” as waves of contraction along a hollow muscular structure (such as a rectum) that squeeze the contents onward. With five eye-popping, ass-expanding scenes that expose pretty girls’ buttholes consuming, hiding and then squeezing out wild-ass foreign objects (and one big, black cock), director Jay Sin’s “Anal Acrobats 5” might be defined as a graphic look at peristalsis, with surreal and cartoonish flourishes. Jay has assembled his usual, stunning array of fun loving, flexible vixens, and his vivid camera work captures their anally acrobatic exploits. Over and over he presents crystal close-ups of that breathtaking moment when a big ball or toy stretches the anus to maximum wideness, perched precariously in the pink threshold, about to be either sucked back into the warm, wet confines or expelled with a pop, leaving the asshole to gape open or wink closed.