What happens to a turkey sandwich after it enters your mouth?
A turkey sandwich is made up of bread, lettuce, mayo, turkey, and cheese. The bread is rich in carbohydrates but also includes other nutrients like proteins, fiber, vitamins and some minerals. Lettuce is rich in fiber and turkey provides proteins along with some other nutrients. Mayonnaise provides fat and cheese provides fat and vitamins. These nutrients need to be absorbed by the body and for this to happen, they must first be digested by the body.
Like all other food, the digestion of a turkey sandwich starts in the mouth. The teeth break down the food in to small pieces. The saliva from the salivary glands contains the enzyme amylase which breaks down carbohydrates to some extent and it also eases the passage of food through the esophagus, the tube which takes the food down to the stomach.
In the stomach, the food is churned in the presence of pepsin which breaks down proteins. Then the food is pushed to the duodenum, where all the enzymes and digestive fluids from the pancreas and the liver are mixed with churned food thus helping to break it down. The small intestine then absorbs the nutrients and sends the nutrient-free food to the large intestine. In the large intestine, the water is absorbed and the solid waste is eliminated from the body through the rectum.
Thus we see that the process of digestion is very long and complicated and that the food we eat goes down several steps before we get energy from it. The process of digestion breaks carbohydrates down to glucose, proteins down to amino acids, fats down to fatty acids and glycerol, thus releasing ATP. Vitamins and minerals are utilized for the growth and repair of the body. We start chemical and mechanical digestion as soon as the food enters the mouth. But who thinks of all this while taking the juicy bite of that turkey sandwich with mayonnaise dripping from its sides?