Spiral valve

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A spiral valve or scroll valve is the corkscrew-shaped lower portion of the intestine of some sharks, Acipenseriformes (sturgeon and paddlefish), rays, skates, bichirs, Lepisosteiformes (gars), and lungfishes. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine which increases nutrient absorption.^[1]