Why is stomach shaped like sac?

The stomach is shaped like a sac to accommodate the varying amounts of food and liquid it needs to digest. This flexible, expandable structure allows it to stretch when filled, facilitating the mixing of food with digestive juices. The sac-like shape also aids in the mechanical breakdown of food through muscular contractions, known as peristalsis, which helps propel the contents toward the small intestine for further digestion and nutrient absorption.