Digestion and the Digestive System Enzymes
The first stage of digestion takes place in the mouth. Salivary glands located under the tongue, and in the back of the mouth, produce saliva in the mouth. Enzymes in the saliva start the chemical digestion of food. Amylase starts the breakdown of carbohydrates, while salivary lipase begins the breakdown of fats.
Once the food arrives at the stomach, gastric glands secrete pepsinogen and hydrochloric acid. Pepsinogen helps with the digestion of protein. Hydrochloric acid kills bacteria in the food, and creates the optimal pH balance for gastric enzymes to function. This process turns the food stuffs into chyme.
The chyme then enters the small intestine where digestive enzymes from the pancreas assist in the further breakdown of fats, proteins, and carbohydrates. Digestive enzymes in the small intestine include: trypsin for breaking down protein; pancreatic lipase to break down fat; and, pancreatic amylase to break down carbohydrates. Bile from the gallbladder also aids in the digestion and absorption of fats in the small intestine.
The small intestine is responsible for most chemical digestion of food, and absorption of nutrients including proteins, fats, and carbohydrates. Once the small intestine has extracted the nutrients, the remaining waste proceeds to the large intestine. Here water and salts are removed before the waste is expelled from the body.