Spiral valve 1005971 180595298 2007-12-28T11:55:50Z SmackBot 433328 Standard headings &/or gen fixes. using [[Project:AutoWikiBrowser|AWB]] A '''spiral valve''' is the lower portion of the [[gastrointestinal tract|intestine]] of some [[shark]]s, [[batoidea|ray]]s, [[skate]]s and [[bichir]]s. A modification of the [[ileum]], the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption. The intestines of a shark are much shorter those of mammals. Sharks have compensated for this problem by having a spiral valve, or a scroll valve, inside the intestine to increase the absorbent surface of the intestine. By keeping [[digest|digestible]] material in the ileum for an extended period of time maximum nutrient absorption is ensured. For this reason, many sharks and related [[fish]] feed very infrequently. The food passes into the comparatively short [[colon]] of the shark almost fully digested, and then out the [[cloaca]] and [[vent]]. {{sharksportal}} ==See also== * [[Small Intestine]] * [[Physical characteristics of sharks]] [[Category:Animal anatomy]] [[Category:Sharks]] {{Shark-stub}}