Stomach

The stomach is a muscular, hollow, dilated part of the digestion system which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects (mid-gut), and molluscs. It is involved in the second phase of digestion, following mastication (chewing).
The stomach is located between the esophagus and the small intestine. It secretes protein-digesting enzymes and strong acids to aid in food digestion, (sent to it via oesophageal peristalsis) through smooth muscular contortions (called segmentation) before sending partially digested food (chyme) to the small intestines.

Worms

Intestinal worms or stomach worms are mostly found in the gastro-intestinal tract of a person, primarily on the intestinal wall. Intestinal worms mostly strike during the rainy season. Stomach worms can be tapeworms, threadworms, hookworms, pinworms or roundworms. Stomach worms are quite common in children. Stomach worms can cause pain in the stomach as well as during motions. Eating contaminated food or eating food with dirty fingers can lead to intestinal worms. Not washing your hands frequently is also a possible cause for intestinal worms.