A turkey is made from meat which is high in protein. Protein is mostly digested in the stomach.
The sandwich made by wheat bread which was high in carbohydrate. Carbohydrate can be digested by saliva and the enzyme secreted in the small intestine.
Mayonnaise is oily and has high-fat content. Fat will be broken down using bile acid and enzyme in the small intestine.
Lettuce is mostly fiber which will not be digested and absorbed by the human. But it could be fermented by some o the gut bacteria.
