Digestive System

Summary

The digestive system is responsible for breaking down food into nutrients, which the body uses for energy, growth, and cell repair. It involves a series of organs that convert food into absorbable nutrients and expel waste.

• Alimentary Canal — a long tube running from the mouth to the anus, part of the digestive system. Example: The journey of food through the alimentary canal involves ingestion, digestion, absorption, assimilation, and egestion.
• Peristalsis — muscular contractions that move food through the digestive tract. Example: Peristalsis pushes food down the oesophagus to the stomach.
• Physical Digestion — the mechanical breakdown of food into smaller pieces. Example: Teeth grinding food in the mouth.
• Chemical Digestion — the breakdown of food using enzymes. Example: Salivary amylase in saliva breaking down starch into maltose.
• Stomach — a muscular organ where food is mixed with gastric juices for digestion. Example: Pepsin in the stomach breaks down proteins into peptides.
• Small Intestine — the site where most nutrient absorption occurs. Example: Villi in the small intestine absorb nutrients into the bloodstream.
• Large Intestine — absorbs water and forms faeces. Example: The colon absorbs remaining water from indigestible food matter.

Exam Tips

Key Definitions to Remember

• Alimentary Canal: The long tube from mouth to anus involved in digestion.
• Peristalsis: Muscular contractions moving food through the digestive tract.
• Physical Digestion: Mechanical breakdown of food.
• Chemical Digestion: Breakdown of food using enzymes.

Common Confusions

• Confusing physical digestion with chemical digestion.
• Misunderstanding the role of the stomach versus the small intestine in digestion.

Typical Exam Questions

• What is the role of the stomach in digestion? The stomach mixes food with gastric juices and begins protein digestion.
• How does peristalsis aid digestion? Peristalsis moves food through the digestive tract by muscular contractions.
• Where does most nutrient absorption occur? In the small intestine.

What Examiners Usually Test

• Understanding the sequence of digestion: ingestion, digestion, absorption, assimilation, egestion.
• The role of enzymes in chemical digestion.
• Differences between physical and chemical digestion.