Digestive System A&P Practice Test

The folds that let the stomach expand are called rugae. These are mucosal and submucosal folds that appear prominent when the stomach is empty. As you eat and the stomach fills, the rugae unfold and the stomach walls stretch, allowing a large volume to be accommodated without a rigid, fixed shape. The other terms refer to folds in other parts of the digestive tract or to microscopic structures: plicae are circular folds mainly in the small intestine that increase surface area; haustra are pouch-like segments of the colon; microvilli are tiny projections on epithelial cells to boost absorption. So the stomach’s ability to enlarge during food intake comes from the rugae.