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Award in
Nutrition for Healthy Living
Lesson 1: Structure and Function
of the Digestive System
Unit 1
Food Groups and Digestion
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Lesson 1 Learning Objectives
• Understand the structure and functions of the
digestive system
• Outline the roles of the digestive organs
• Describe movement through the digestive
system
• Describe the role of digestive enzymes
• Describe digestion of carbohydrates, fats and
proteins
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Functions of Digestive System
• Breakdown of foods
• Extraction of nutrients for use around the body
• Extraction of water for use around the body
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Structure of Digestive System
• Mouth
• Oesophagus
• Stomach
• Duodenum
• Small intestine
• Large intestine (including
colon and rectum)
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Role of Digestive Organs - Mouth
•
•
•
•
Teeth and saliva work to breakdown food
Saliva contains the ENZYME SALIVARY AMYLASE
Breaks starch in to sugars
Passes easier along the oesophagus
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Role of Digestive Organs –
Oesophagus
STRUCTURE
• Muscular tube
• Leads the pharynx to the stomach
• First key organ in the digestion process
FUNCTION
• Carry food to stomach
• Moves via muscular contraction
• Known as peristalsis
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Role of Digestive Organs – Stomach
STRUCTURE
• Rounded and hollow
• Innermost layer (mucosa – mucous membrane)
• Elastic – expanding and relaxing
• Sphincters at top and bottom prevent back flow
and ensure control
• Food enters from oesophagus and leaves into the
duodenum (1st part of the small intestine)
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Role of Digestive Organs – Stomach
FUNCTION
• Digests proteins and fats through enzymatic
reactions
• Gastric juices breaks down food further
• Absorbs alcohol
• When food is partly digested, the mass is known
as chyme
• Chyme moves from stomach to small intestine
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Role of Digestive Organs – Small
Intestine
STRUCTURE
• 7 metres long
• 3 sections (duodenum, jejunum and ileum)
• Inner wall covered in villi, tiny finger like projections
which increase area for absorption
FUNCTION
• Completes the chemical digestion process
• Absorption of nutrients take place here
• Absorbed through the villi into blood
• Site for water absorption too
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Role of Digestive Organs - Pancreas
STRUCTURE & FUNCTION
• Behind the stomach
• Works with digestive and endocrine system to
produce enzymes
• Pancreatic enzymes break down CHO, protein
and fat
• Break down food, stores insulin and glucagon
(glycogen back to glucose)
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Role of Digestive Organs – Gall
Bladder
STRUCTURE
• Pear shaped
• Stores bile made from the liver
• Bile used to digest food
• Bile emulsifies fat and allows for absorption of
fats
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Role of Digestive Organs –
Duodenum
• Monitors content of chyme via sensors
• Proteins and fats cause hormone to released bile
from gall bladder
• Bile reaches duodenum where is breaks fats
down by enzyme pancreatic lipase
• Absorption of vitamins, minerals and nutrients
takes place here
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Role of Digestive Organs – Jejunum
• Section where the villi line the walls
• The majority of absorption is carried out in this
section
• Simple sugars, water soluble vitamins and amino
acids
Role of Digestive Organs – Ileum
• Final stages of absorption occur
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Role of Digestive Organs
Duodenum
Jejunum
Ileum
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Role of Digestive Organs – Large
Intestine
STRUCTURE
• 1.5m long
• Four sections: caecum, appendix, colon and rectum
• Deals with waste
FUNCTIONS
• Formation of Vit B and K
• Reabsorb remaining water
• Eliminate waste and undigested foods
• Results in faeces – passed to colon
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Peristalsis
• Term used for the movement of food through
digestive system
• A series of smooth muscular contractions
Contraction
Muscular Wall
Chyme
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Digestive Enzymes
Organ
Secretion
Action
Mouth
Salivary Glands
Salivary amylase
Converts starch into sugars
Pancreas and
Duodenum
Lipase
Stomach
Pepsin
Coverts fats into fatty acids
Digestion of proteins
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Summary Video
External Video available in Resources Section
https://www.youtube.com/watch?v=b20VRR9C37Q
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Summary
• Identified the structure of the digestive system
• Determined the route which food takes in order
to be digested
• Identified that the small intestine has 3 sections
and each are important for the absorption of
nutrients
• Highlighted the key enzymes responsible for
digestion
• Described the process of digestion of
carbohydrates, proteins and fats.
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ANY QUESTIONS?
If you need any support please do not
hesitate to get in contact with your
mentor.
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Activities
• Complete the Quiz
‘Quiz Yourself from Lesson 1’
• Label the blank Digestive System
Diagram
• Download/Print any resources you
need for Lesson 2
• Take a 15 minute break
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End of Lesson 1
Complete your quiz…
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