Pyloric sphincter, pill camera view. This sphincter is a ring of muscle that controls the passage of food from the stomach to the duodenum of the small intestine. The sphincter is closed here. The stomach is responsible for chemically and mechanically breaking down food before passing it to the small intestine, where nutrients are absorbed. The sphincter remains closed until the food is sufficiently broken down. The lining (mucosa) of the stomach is highly folded. This allows for expansion to accommodate food, and increases the surface area from which mucus and stomach acid can be released. A pill camera is a pill-sized camera that is swallowed to image the digestive tract.