1. Frehana Ali1 The Gut Wall

2. 2 The Gut Wall The gut wall is divided into 3 main layers: An outer muscle layer, protected by a thin coating of fibres A middle layer, called the submucosa An inner layer, called the mucosa

3. 3 The structure of the gut wall is not the same all along the gut. The layers have special features in different regions that allow that part of the gut to carry out specific functions. The different regions are: Oesophagus Stomach Duodenum Ileum

4. 4 Oesophagus Main function - To push food to the stomach. Muscle layer – Two thick layers force solid food along by peristalsis. Submucosa – Elastic to allow expansion as food passes. Glands secrete mucus to lubricate passage of food. Mucosa – Lining has several layers of flattened cells; outer layers can be rubbed off as food passes without causing damage to cells underneath. Folds allow expansion as food passes.

5. 5 Stomach Main function – Temporary food store. Muscular churning mixes and breaks up food. Hydrochloric acid produced kills micro organisms in food. Some digestion. Muscle layer – Three layers run in different directions. As the layers contract and relax, this creates an effective churning action Submucosa – Separates muscular and glandular layers. Mucosa – Layer is thick with deep pits. These contain many glands that secrete mucus, enzyme and acid.

6. 6 Doudenum (first 25cm of small intestine) Main function – Neutralisation of stomach acid. Point of entry for Pancreatic juice and bile. Digestion and some absorption. Muscle layer – Two layers for peristalsis. Submucosa – Contains Brunners glands that secrete alkaline mucus. This helps to neutralise stomach acid. Mucosa – Contains many glands that secrete mucus and enzymes. Folded into numerous projections called villi. These increase the surface area for absorption of digested food.

7. 7 Ileum (lower part of small intestine) Main function – Completion of digestion. Absorption of products of digestion. Muscle layer – Two layers peristalsis. Submucosa – Contains many blood and lymph vessels that take up absorbed food and transport them around the body. Mucosa – Similar to Duodenum, but fewer glands. Patches of cells called Paneth cells, at base of glands, which help defend against bacterial infection. Some enzyme production.