The transmitter for relaxation is therefore not acetylcholine. As the waves approach the pylorus they become deeper, so that the waves raise the pressure within the narrower parts of the pyloric antrum. However, because of the small diameter of the exit and because of incomplete occlusion of the lumen of the antrum, regurgitation occurs back into the wider part of the antrum. This produces good mixing and if there are large particles within the stomach, this activity can break them down. These factors have been extensively studied by swallowing foods of known composition and then sampling the contentsof the stomach at fixed times afterwards, using stomach tubes.
Fats also reduces the rate of emptying.
However, the greater the volume of food in the stomach, the faster is the rate of gastric emptying. Small Intestine . The properties and names of the small intestine vary along its length. The stomach leads into the duodenum which is followed by the jejunum and then by the ileum. Activity in the muscularis mucosae moves the villi which aids absorption by ensuring that the epithelial cells are frequently brought into contact with fresh material.