The organ in the body primarily responsible for digestion is the stomach. This muscular organ plays a critical role in breaking down food into a semi-liquid form called chyme. The stomach secretes digestive enzymes and acids that help to further digest proteins and kill harmful bacteria. It also serves as a temporary storage space for food before it moves on to the small intestine, where most nutrient absorption occurs. The stomach's rhythmic contractions, known as peristalsis, mix food with digestive juices and facilitate its passage through the digestive tract.