Mechanical digestion refers to the physical breakdown of food, whereas chemical digestion pertains to the enzymatic breakdown of food substances.

Mechanical digestion primarily involves the physical fragmentation of food into smaller, more manageable pieces. This process enhances the surface area available for subsequent chemical digestion. It begins in the mouth, where teeth grind and mash the food. The process continues in the stomach, where muscular contractions churn the food and mix it with digestive juices. Additionally, mechanical digestion is facilitated in the small intestine, where peristaltic contractions further mix and propel the food along the digestive tract.

On the other hand, chemical digestion entails the enzymatic breakdown of food molecules into smaller, absorbable units. This process also initiates in the mouth, where the enzyme amylase begins to break down carbohydrates. In the stomach, hydrochloric acid and various enzymes contribute to the breakdown of proteins. The majority of chemical digestion occurs in the small intestine, where enzymes from both the pancreas and the intestinal lining act on carbohydrates, proteins, and fats to convert them into absorbable nutrients.

In summary, mechanical and chemical digestion work in tandem to decompose food and prepare it for absorption into the bloodstream. Mechanical digestion physically reduces food into smaller pieces, while chemical digestion employs enzymes to transform food molecules into nutrients that can be absorbed by the body.