Physical Digestion

Physical digestion, also known as mechanical digestion, is the process of breaking down food into smaller pieces without altering the chemical composition of the food molecules. It occurs primarily in the mouth and stomach through the action of mechanical forces, such as chewing and stomach churning.

Chewing 

• The process of chewing food in the mouth is the first step of physical digestion.

 As food enters the mouth, the teeth grind and crush it into smaller pieces. The tongue helps mix the food with saliva, forming a soft mass called bolus. Chewing, also known as Mastication not only reduces the food’s size but also increases its surface area, making it easier for enzymes to access the food particles during chemical digestion.

Stomach Churning 

• Once the bolus is formed, it is swallowed and passes through the esophagus into the stomach. 

In the stomach, the muscular walls contract and relax in a rhythmic motion, churning and mixing the food with gastric juices. This process further breaks down the bolus into smaller fragments and mixes it with the stomach’s acidic environment.

By breaking the food into smaller pieces, it increases the food’s surface area, facilitating the action of enzymes during chemical digestion. The increased surface area allows the enzymes to come into contact with the food molecules more efficiently, speeding up the overall digestion process.

Chemical Digestion and Enzymes

After the food is broken down into smaller pieces through physical digestion, it moves to the stomach and then to the small intestine for chemical digestion. Chemical digestion involves the action of enzymes, which are specialized proteins that break down large food molecules into smaller nutrients that the body can absorb and use.

Enzymes work like tiny “chemical scissors” that cut large food molecules into smaller pieces. 

Each type of enzyme is designed to break down a specific type of nutrient. For example, 

• Amylase breaks down starch into smaller sugar molecules

• Lipase breaks down fats into fatty acids and glycerol.

Effect of Increased Surface Area

When the food is already in smaller pieces due to physical digestion, enzymes have more places to attach and work on the food molecules. The increased surface area allows the enzymes to have greater contact with the food particles. As a result, the chemical digestion process becomes more efficient and faster.

Without physical digestion increasing the food’s surface area, the chemical digestion process would be less effective, leading to inadequate nutrient absorption and potential health problems.