Transcript The Gut Wall - A level biology

The Gut Wall
Frehana Ali
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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
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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
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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.
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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.
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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 Brunner’s 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.
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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.
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