Digestion: The breakdown of large, insoluble food molecules into small, soluble molecules that can be absorbed into the blood.
Mechanical digestion: Physical breakdown of food into smaller pieces without changing the chemical structure (e.g., chewing, churning in the stomach).
Chemical digestion: Breakdown of food molecules by enzymes into smaller molecules (e.g., amylase breaking starch into maltose).
Peristalsis: Wave-like contractions of circular and longitudinal muscles in the alimentary canal wall that push food along the digestive tract.
Bile: An alkaline fluid produced by the liver and stored in the gall bladder; emulsifies fats and neutralises stomach acid in the small intestine. It is not an enzyme.
Villi (singular: villus): Finger-like projections lining the small intestine wall; massively increase surface area for absorption of digested nutrients.
This definitions covers Key Definitions within The Human Digestive System for GCSE Biology. Structure and function of digestive organs, mechanical and chemical digestion, enzymes, absorption, and practical investigations It is section 9 of 15 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Practice questions for The Human Digestive System
Which organ produces hydrochloric acid to kill bacteria in food?
Explain the role of bile in the digestive system.
Quick recall flashcards
What are villi?
Villi are tiny finger-like projections on the wall of the small intestine that greatly increase the surface area for absorption of nutrients.
What is peristalsis?
Peristalsis is the wave-like contractions of smooth muscle that push food through the digestive system. Circular muscles contract behind food while longitudinal muscles relax in front.