The Digestive System

To successfully navigate the L2 Gym Instructing qualification, you will need an understanding of ‘The Digestive System’.

We have developed a simple cheat sheet, that will help you.


What you will learn

  • What is the digestive system
  • The basic structure of the digestive system
  • The four stages of Digestion
  • The journey through Alimentary Canal



What is the Digestive System?

The digestive system is responsible for the intake, breakdown, use and removal of food and drink.
It tells us we’re hungry, full & thirsty.
It does all of this through the Autonomic Nervous System (ANS).

Four stages of Digestion

There are four stages of the digestive system:

  1. Ingestion – Food is chewed in the mouth
  2. Digestion – Breakdown of food, through mechanical and smooth process… basically the release of enzymes
  3. Absorption – Passing of food/nutrients to the bloodstream, which will then be used by the body
  4. Elimination – Removal of waste

Journey through Alimentary Canal

The alimentary canal is also known as the digestive tract, the gastro tact or the gut.
When food makes its journey through the alimentary canal, it can take up to 24 hours.
The whole of the alimentary canal can cover a distance of nine metres, from ingestion at the mouth to excretion at the anus.
Let’s take a look at the journey that food makes as it goes through the Alimentary Canal.
The mouth is the point where food enters the body.
Once there, our teeth rip and grind it into smaller pieces.
Saliva moistens the food and saturates it with enzymes, this is where the breakdown of food starts.
The tongue then pushes the food down the throat, to swallow.
The Esophagus is a thick-walled muscular tube, that carries the broken food from the mouth to our stomachs.
The saliva that moistens the food in the mouth, helps to transport the food through the Esophagus with a mucus membrane.
Gravity does most of the work, a series of wave-like contractions (Peristalsis) does the rest.
From the Esophagus, the food enters the stomach.
The stomach is a J shaped, muscular bag, located on the left side of the upper abdomen
Whilst most nutrients can be absorbed in the small intestine, the stomach can also absorb some nutrients.
The food is churned up and mixed with a liquid called ‘Chyme’
The Chyme then goes through another ring-like muscle (pyloric sphincter), and enters the small intestine.
This process is quite slow, it can take between 1-4 hours for the stomach to empty depending on what we have eaten.
Carbs empty first, then protein.
Whereas fats and fibre move through the slowest.
Small intestine
The small intestine is a small, tightly folded tube, that receives the Chyme from the stomach.
It’s the major site of digestion within the alimentary canal.
The role of the small intestine is to absorb nutrients into the bloodstream, to pass to the body tissues, to be used as energy.
Peristalsis moves things through the small intestine very slowly, it can take between 4-8 hours for the Chyme to travel through the small intestine.
This slow pace is a good thing, as it allows the small intestine time to absorb most of the nutrients eaten.
Large intestine
The large intestine is the final part of the digestive system.
It absorbs water and vitamins from food residue.
It then forms and stores faeces, ready for excretion.
The large intestine is made up of the colon and rectum, which is basically the passageway for faeces.
Which then leads to the anus, a valve-like exit at the end of the alimentary canal.
Food can stay in the large Intestine for between 12-25 more hours, moving along at only 5cm per hour before being excreted as waste.

To wrap things up

To successfully complete the Level 2 Gym Instructing qualification, you will need a basic understanding of the digestive system.

Practice presenting the following slide.

If you can do this without looking at any course materials, you have all the knowledge you need to successfully complete this part of the course






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