The organ primarily responsible for digestion is the stomach. When food enters the stomach, it is mixed with gastric juices containing hydrochloric acid and enzymes, which help break down proteins and kill harmful bacteria. The stomach's muscular contractions aid in churning the food into a semi-liquid mixture called chyme. This process also prepares the food for further digestion and nutrient absorption in the small intestine. The stomach plays a crucial role in the digestive system, working alongside other organs such as the esophagus, small intestine, and pancreas to ensure that nutrients are effectively absorbed into the bloodstream.