Ashwini Mudra is done by contracting the anal sphincter muscles in a rhythmic manner. (yogicwayoflife.com)
Ranging from the size of pea to the size of a hazelnut, the anal sacs are embedded between the internal and external anal sphincter muscles on each side of the anus. (dogcare.dailypuppy.com)
Sometimes called the rest and digest system, the parasympathetic system conserves energy as it slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in the gastrointestinal tract. (sciencedaily.com)