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Digestive 
Systems

Multicellular organisms contain systems of organs that carry out specialised functions that enable them to survive and reproduce.

The Human Digestive System

Outline the role of the digestive system in supporting life processes.
 

The digestive system plays a crucial role in supporting various life processes by facilitating the breakdown of food into nutrients that can be absorbed and utilized by the body. Here is an outline of the key roles of the digestive system:
 

Ingestion: Takes in food through the mouth to start the digestion process.
 

Digestion: The breaking down of food into smaller pieces and simpler units. 

 

Absorption: Moves nutrients from the digestive tract to the bloodstream for energy and bodily functions.
 

Transportation: Moves ingested food along the digestive system for optimal digestion.
 

Elimination: Expels indigestible materials to maintain a healthy internal environment.

ACTIVITY 1: Colour, Symbol Image​

CSI: Circulatory System - Visible Thinking Routine
(Printable Template)

By the end of this section, you should be able to:
 

Digestive Organs

Identify the organs of the digestive system and briefly outline their function.

The digestive system processes food, extracts nutrients, and eliminates waste through a network of organs. Key components and their functions include:
 

Mouth: Starts digestion by chewing and enzyme action.
 

Esophagus: Muscular tube that moves chewed food to the stomach through peristalsis.
 

Stomach: Muscular organ for mechanical and chemical digestion with gastric juices.
 

Small Intestine: Main site for digestion and nutrient absorption, divided into three segments. Enzymes and bile aid in breakdown, and nutrients are absorbed into the bloodstream.
 

Liver: Produces bile for fat digestion, detoxifies chemicals, and metabolizes nutrients.
 

Gallbladder: Stores and releases bile to aid fat digestion.
 

Pancreas: Secretes digestive enzymes and regulates blood sugar.
 

Large Intestine (Colon): Absorbs water and electrolytes, forms feces, houses bacteria aiding fermentation.
 

Rectum: Stores feces until elimination.
 

Anus: Opening for feces expulsion during defecation.

BIO [LS]_Digestive System (Diagram).png

ACTIVITY 2: Digestive System - Play Doh Model

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Familarise yourself with the organs of the digestive system by building a Play Doh model. 

BIO [LS]_Digestive Play Doh (PA).jpg

Digestive System Play Doh
(Printable Template)

ACTIVITY 3: Digestive Anatomy - Labelling Game
 

Test your knowledge
of digestive anatomy
using this online
labelling interactive. 

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Digestive Anatomy

(Online Simulation)

Physical & Chemical Digestion

Compare physical (mechanical) digestion and chemical digestion.​

ACTIVITY 4: White Bread Digestion

​

1. Chew some white bread in your mouth. This chewing is physical digestion. 

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2. Hold the chewed bread in your mouth for about a minute (don't swallow yet). Do you notice any changes to the taste?

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3. Propose a reason why the bread starts to taste different. 

BIO [LS]_White Bread Digestion (IMAGE).png
BIO [LS]_Types of Digestion (IMAGE).PNG

FORMATIVE ASSESSMENT 1: Types of Digestion

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Types of Digestion

(Formative Assessment)

Types of Digestion

(Answer Key)

Physical (mechanical) digestion and chemical digestion are two distinct processes involved in breaking down food into smaller, absorbable components in the digestive system. They work in concert to prepare nutrients for absorption and utilization by the body. Here's a comparison between the two:

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Physical (Mechanical) Digestion:

  • What it does: Breaks down food into smaller pieces.

  • How it works: Involves chewing, grinding, churning, and emulsifying (by bile).

  • Where it happens: Mainly in the mouth (chewing), stomach (churning), and small intestines (emulsification by bile).

  • Why it's important: Makes food smaller and mixes it with digestive juices.
     

Chemical Digestion:

  • What it does: Breaks down food into simpler substances.

  • How it works: Involves enzymes causing chemical reactions.

  • Where it happens: Starts in the mouth (carbohydrates), continues in the stomach (proteins) and small intestine (all nutrients).

  • Why it's important: Changes food into their simplest units (sugars, amino acids, and fatty acids) for the body to use.

Digestive Enzymes

Describe what an enzyme is and its role in digestion.

ACTIVITY 5: Observing Enzyme Action
 

Conduct an investigation to observe how enzymes breakdown food.

BIO [LS]_Pineapple Investigation (IMAGE).PNG

Observing Enzymes

(Worksheet)

Observing Enzymes

(Model Answers)

Observing Enzymes

(Projectable instructions)

Enzymes are like tiny helpers in our body that make it easier to turn big pieces of food into small pieces our body can use. In digestion, they chop up food into tiny parts so our body can absorb the nutrients and get energy from them. There are over 700 enzymes in the human body and each one is specific to one particular chemical reaction.

 

Here are some examples:

  • Lipase is the name we call enzymes that breakdown fats (lipids). 

  • Amylase is the name we call enzymes that breakdown carbohydrates.

  • Protease is the name we call enzymes that breakdown proteins. 

​

BIO [LS]_Digestive Enzymes (CARTOON).PNG
BIO [LS]_Process of Digestion (DIAGRAM).jpg

Journey Through the Digestive Tract

Describe the path food takes through the digestive tract and outline the digestive processes that take place along the way.

The organs of the digestive system ​can be divided into two groups:
 

The digestive tract​:

  • Other names: the alimentary canal or ​gastrointestinal tract (G.I. tract)

  • Role: The digestive tract is the pathway by which food enters the body and solid wastes are expelled. ​

  • Organs: 

    • Mouth (oral/buccal cavity)​

    • Pharynx (throat)​

    • Oesophagus​

    • Stomach​

    • Small intestine​

    • Large intestine​

    • Rectum & anus
       

Accessory organs:

  • Role: The digestive system has accessory organs that are not a part of the digestive tract but aid in the digestive process. 

  • Organs: ​

    • Tongue​

    • Salivary glands​

    • Liver​

    • Pancreas​

    • Gall bladder

ACTIVITY 6: 
Complexity Scale

Complexity Scale - Visible Thinking Routine
(Printable Template)

Absorption in the Small Intestine

Explain how high surface area in the small intestine aids in nutrient absorption.

The small intestine has a high surface area, mainly due to its specialized structure, which includes finger-like projections called villi and microvilli. This increased surface area is crucial for efficient nutrient absorption. 


Villi and Microvilli: The inner lining of the small intestine is covered with tiny finger-like projections called villi. Each villus, in turn, has even smaller projections known as microvilli. These structures significantly increase the surface area available for absorption.
 

Increased Contact with Nutrients: As food is digested and moves through the small intestine, it comes into contact with the numerous villi and microvilli. The extensive surface area allows for more contact between the digested nutrients and the absorptive cells of the small intestine.​

ACTIVITY 7: Investigating Villi Action

​

Conduct an experiment simulating absorption by villi.  

BIO [LS]_Villi Absorption (IMAGE)_edited

Investigating Villi Action

(Science Inquiry Skills)

BIO [LS]_Villi & Micro Villi (DIAGRAM).png

FORMATIVE ASSESSMENT 2: The Digestive System

​

The Digestive System

(Formative Assessment)

The Digestive System

(Answer Key)

FORMATIVE ASSESSMENT 3: The Digestive System

​

The Digestive System

(Formative Assessment)

The Digestive System

(Answer Key)

Other Digestive Systems

Compare the digestive system of humans (omnivores) with organisms that have different diets.

Complete these activities as an introduction to the content.

ACTIVITY 7: Comparing Digestive Systems

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STEP 1: Observe the digestive anatomy of a lion and a koala. Discuss and differences you observe. 

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STEP 2: Construct a Venn diagram summarizing the differences in herbivore and carnivore digestive systems. The overlapping section of the Venn diagram should represent omnivores. 

STEP 3: Add information you already know about each digestive system, based on prior knowledge or from discussions relating to the "Spot the Difference" thinking exercise. 
 

STEP 4: Draw on resources (such as the internet) to add information and images to your Venn diagram. 

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STEP 5: Swap idea's with peers to add even more ideas to your Venn diagram. 

Spot the Difference

(Thinking Exercise)

Venn Diagram

(Graphic Organiser)

Omnivore, Carnivore & Herbivore Digestive Systems

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The digestive systems of organisms are adapted to their specific diets, and they vary significantly based on whether an organism is an herbivore, carnivore, omnivore, or other specialized feeder. Let's compare the digestive system of humans (omnivores) with those of herbivores and carnivores.

FORMATIVE ASSESSMENT 4: Other Digestive Systems

​

Other Digestive Systems

(Formative Assessment)

Other Digestive Systems

(Answer Key)

Review & Consolidation

Reflect on your achievement of the learning goals. 

 

  • LG1 - Outline the role of the digestive system in supporting life processes.
    ​

  • LG2 - Identify the organs of the digestive system and briefly outline their function.
     

  • LG3 - Compare physical (mechanical) digestion and chemical digestion.
    ​

  • LG4 - Describe what an enzyme is and its role in digestion.
     

  • LG5 - Describe the path food takes through the digestive tract and outline the digestive processes that take place along the way.
     

  • LG6 - Describe how exchange of nutrients occurs between the villi & microvilli of the small intestine with the blood.
     

  • LG7 - Explain how high surface area in the small intestine aids in nutrient absorption.
     

  • LG8 - Compare the digestive system of humans (omnivores) with organisms that have different diets.

ACTIVITY 8: Journey of a Cheese Sandwich​

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Journey of a Cheese Sandwich (Creative Consolidation Task)

Check out these amazing student examples!

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