This topic summary covers Knowledge Organiser 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 13 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 13 of 15
Practice
19 questions
Recall
24 flashcards
Knowledge Organiser
Key Terms
- Digestion: Breakdown of large insoluble molecules to small soluble ones
- Peristalsis: Wave-like muscle contractions that move food along
- Bile: Alkaline fluid that emulsifies fats (NOT an enzyme)
- Villi: Finger-like projections that increase absorption surface area
- Emulsification: Breaking large fat droplets into smaller ones
- Chyme: Acidic liquid mixture leaving the stomach
Must-Know Facts
- Small intestine surface area ~200 m² (tennis court) due to villi and microvilli
- Bile is produced by the liver, stored in the gall bladder
- Pancreas produces amylase, lipase, and protease enzymes
- Large intestine absorbs water only — no nutrients
- Fats are absorbed into lacteals (lymph vessels), not blood capillaries
- Stomach produces hydrochloric acid (pH 1.5–3.5) and pepsin
- Peristalsis allows food to travel upwards — gravity is not needed
- Hepatic portal vein carries absorbed nutrients from intestine to liver