Gastric juice is comprised of water, digestive enzymes, mucus, electrolytes, intrinsic factor and hydrochloric acid. Enzymes in gastric juice include pepsinogen, gastric lipase and amylase.
Each component of gastric juice has a important role. Hydrochloric acid lowers the pH of the stomach, breaks down nutrients and kills bacteria. Pepsinogen helps break down proteins, gastric lipase breaks down fats and amylase breaks down carbohydrates. Intrinsic factor helps the body absorb vitamin B-12. Mucus is secreted by the neck cells and coats the stomach lining to protect it from all the acids.
The stomach muscles squeeze and churn to combine the chewed food with the gastric juices to create a mixture called chyme. After a period of time, the stomach squeezes the chyme into the small intestine, which further digests and absorbs the food.