Mechanical and Chemical Digestion

Mechanical Digestion

Mechanical digestion begins in the mouth where the teeth grind food into smaller pieces. This increases the surface area of the food, making it easier for enzymes to break down.
The tongue moves the food around the mouth for thorough mixing with saliva, which moistens the food for easier swallowing.
Swallowing, or deglutition, is a complex muscle movement that pushes the food from the mouth into the oesophagus.
In the oesophagus, waves of muscle contractions called peristalsis move the food down into the stomach.
The stomach acts like a muscular mixer, churning and kneading the food while gastric juices break it down further. This forms a semi-liquid mass called chyme.

Chemical Digestion

Chemical digestion also starts in the mouth, where the enzyme amylase in saliva begins to break down carbohydrates into simpler sugars.
Once the food reaches the stomach, it comes into contact with acidic gastric juice, which contains hydrochloric acid and the enzyme pepsin. Pepsin begins the process of breaking down proteins.
The highly acidic environment in the stomach denatures proteins, making them more accessible for enzyme activity.
The chyme then moves into the small intestine, where it is combined with bile from the gallbladder, and digestive enzymes from the pancreas. Bile aids fat digestion, whilst pancreatic enzymes continue to break down proteins, carbohydrates, and fats.
Final hydrolysis of these molecules occurs in the small intestine with the help of various enzymes secreted by its walls. These include maltase, sucrase and lactase for carbohydrates; trypsin and chymotrypsin for proteins; and lipase for fats.

Understanding the process of digestion is essential for comprehending how our body uses food to generate energy. It also informs our knowledge of disorders related to digestion and how diet can influence health. Nutrients are effectively extracted by efficient digestion and is the reason why we should maintain a balanced diet.