Gastric juice is a digestive fluid produced by the lining of the stomach. It primarily consists of water, hydrochloric acid, enzymes, and mucus. The hydrochloric acid helps break down food and creates an acidic environment that activates digestive enzymes, such as pepsin, which further aids in protein digestion. This fluid plays a crucial role in the digestive process by breaking down food into a semi-liquid form called chyme. Additionally, gastric juice helps kill harmful bacteria that may enter the stomach with food, protecting the body from infections and ensuring proper digestion.