Study Notes
The alimentary canal is a part of the digestive system responsible for processing food through various stages.
- Ingestion — Taking substances into the body through the mouth. Example: Eating an apple.
- Digestion — The breakdown of large insoluble food molecules into smaller water soluble molecules by mechanical and chemical means. Example: Chewing bread and mixing it with saliva.
- Absorption — The movement of digested food molecules from inside the small intestine through the wall of the small intestine and into the blood system. Example: Nutrients from digested food entering the bloodstream.
- Assimilation — When digested food molecules are actually used by the body or become a part of the body. Example: Glucose being used for respiration.
- Egestion — Passing out of food that has not been digested as faeces through the anus. Example: Excreting waste after digestion.
Exam Tips
Key Definitions to Remember
- Ingestion: Taking substances into the body through the mouth.
- Digestion: Breakdown of large insoluble food molecules into smaller water soluble molecules.
- Absorption: Movement of digested food molecules into the blood system.
- Assimilation: Use of digested food molecules by the body.
- Egestion: Passing out of undigested food as faeces.
Common Confusions
- Confusing absorption with assimilation.
- Thinking digestion only occurs in the stomach.
Typical Exam Questions
- What is the role of the small intestine in digestion? It absorbs nutrients into the bloodstream.
- How does mechanical digestion differ from chemical digestion? Mechanical digestion involves physical breakdown, while chemical digestion involves enzymes.
- What happens during egestion? Undigested food is expelled from the body as faeces.
What Examiners Usually Test
- Understanding of each stage of the digestive process.
- Differences between digestion, absorption, and assimilation.