Growth in Muscle Layers Causes Wrinkling (image) Harvard University Caption The wrinkling of the inner gut, Harvard researchers found, is intimately linked to the stages of muscle layer differentiation, which produce a series of different physical stresses. Credit Courtesy of L. Mahadevan and Science/AAAS. Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.