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.