GCSE & KS3 Biology - The Digestive System

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** WHAT'S COVERED **
1. The two main roles of the digestive system:
Digestion: The breakdown of large food molecules (carbohydrates, proteins, lipids) into smaller, soluble molecules.
Absorption: The movement of these small molecules from the digestive tract into the bloodstream.
2. The journey of food through the digestive organs and their functions:
Mouth: Role of teeth and salivary glands (producing amylase).
Oesophagus (Gullet).
Stomach: Role of muscular walls, pepsin (protease enzyme), and hydrochloric acid.
Small Intestine: Where most digestion and absorption occurs, involving enzymes like carbohydrase, protease, and lipase.
Pancreas: Production of pancreatic juices containing digestive enzymes.
Liver and Gallbladder: Production of bile by the liver and its storage/release by the gallbladder to neutralise stomach acid and emulsify lipids.
Large Intestine: Absorption of excess water.
Rectum and Anus: Storage and egestion of faeces.
3. Adaptations of the small intestine for efficient absorption:
Large surface area due to villi and microvilli.
Thin walls (single layer of surface cells) for a short diffusion path.
Good blood supply to maintain a steep concentration gradient.

** CHAPTERS **
0:00 Introduction
0:19 Role of the Digestive System
1:20 Organs of the Digestive System
1:51 Mouth
2:52 Oesophagus and Stomach
3:34 Small Intestine, Pancreas & Gallbladder
3:55 Pancreas Function
4:00 Gallbladder & Bile Function
5:14 Small Intestine Function
6:15 Adaptations of the Small Intestine
7:10 Large Intestine, Rectum & Anus

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