The two types of digestion that occur in the alimentary canal are mechanical digestion and chemical digestion.
Mechanical Digestion
Mechanical digestion involves the physical breakdown of food into smaller pieces. This process increases the surface area of the food, allowing enzymes to act more efficiently during chemical digestion. Examples of mechanical digestion include:
- Chewing: The teeth break down food into smaller particles.
- Churning: The stomach muscles contract to mix food with gastric juices.
- Segmentation: Localized contractions mix chyme (partially digested food) with digestive juices in the small intestine.
- Peristalsis: Rhythmic, wave-like contractions that propel food along the alimentary canal.
Chemical Digestion
Chemical digestion involves the breakdown of food molecules into smaller, simpler molecules by enzymes. This process breaks down complex carbohydrates, proteins, and fats into absorbable units. Examples of chemical digestion include:
- Salivary amylase: Enzyme in saliva that begins the breakdown of carbohydrates in the mouth.
- Pepsin: Enzyme in the stomach that breaks down proteins.
- Pancreatic enzymes: Enzymes secreted by the pancreas into the small intestine, including amylase (carbohydrates), lipase (fats), and proteases (proteins).
- Bile: Produced by the liver and stored in the gallbladder; emulsifies fats, increasing the surface area for lipase to act on.
In summary, mechanical digestion prepares food for chemical digestion by increasing its surface area, while chemical digestion breaks down complex molecules into smaller, absorbable units. Both processes are essential for nutrient absorption in the alimentary canal.
