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.

Diarrhea (Dysentery)

Diarrhea is a change in normal bowel habits characterized by frequent passage of loose, fluid stools. This is common with most gastrointestinal disturbances. Acute diarrhea is marked by a sudden onset. Often, mild to moderate diarrhea is associated with antibiotics when the antibiotics destroy normal flora in the gastrointestinal tract. Diarrhea can also be caused by emotional stress, laxatives (factitious, or self-induced), hormonal abnormalities from such disorders as carcinoid syndrome or certain types of pancreative adenomas, or E.coli, usually experienced by travelers.