Why Digestive System Is So Important to the Excretory System?


GRADE - 11

GOAL - The students will learn functions and structures of digestive system and excretory system.


  • Describe functions and structures of the two systems
  • Expain why excretory system is so important to the digestive system
  • Identify ways to keep these systems healthy

LEARNING TASKS - It's another interesting lesson where students get the chance to understand how body systems depend on one another. I will present this lesson in two groups. First - energy system and second - waste system.

Start off with DO NOW questions on the board. "How human's body are similar to the car's engine?" You may get different answers - but look for this one. The human's body uses food as energy to move and leave waste behind. The car's engine uses fuel to move and it leaves poisonous gases behind.

So - the digestive system is the energy system that turns food into fuel for your body. The excretory system is the waste system that removes waste from the body.

The digestive system - breaks down food so that it can enter your bloodstream and can be used.

Here is the simple steps of digestion -

  1. Digestion begins in your mouth when you chew food
  2. The saliva starts initial breaking down of the food
  3. Then - it moves down to the throat where epiglottis blocks food from going into trachea
  4. The muscles of esophagus contract and move the food down to the stomach
  5. In the stomach - food is mixing with the acid
  6. Then - mixed food moves into a small intestine where digestion takes place. Also - needed nutrients are absorbed here
  7. The food that cannot be absorbed enters the colon and becomes waste

Also - display picture to understand better. This picture can be displayed through overhead projector or Smartboard. You choose!

Digestive Process

Let's break the energy system down and see what organs belong here -

  • Salivary glands - they produce saliva and start initial digestion inside the mouth
  • Esophagus - is the tube that connects mouth to the stomach
  • Stomach - is the muscular organ that mixes food and produces digestive juices
  • Liver - is the gland that has many functions - one of them is to help digest fat
  • Gallbladder - it stores digestive juices
  • Pancreas - it produces digestive enzymes
  • Small intestine - the digestion takes place here
  • Colon - it collects waste

Another visual help. Display picture of organs either through overhead projector or Smartboard.

Digestive System

Now - let's talk about how your body takes care of the waste.

Without excretory system your bodies would be filled with waste and you would explode by it. But thankfully we have this system.

After digestion takes place in the small intestine - the rest of the food that didn't get absorbed goes into colon. When colon is full the nerve sends the message to the muscle to push the waste out. That is when you go to the restroom to take number two.

Another very important organs in your bodies are kidneys. Their job is to filter blood. Sometimes it removes water or salts. When it removes water or salt - it is being stored in the bladder as urine. When it's full - that's when you want to go to the restroom and take number one.

So - the connection between these two systems are obvious. The energy system digests food and turns into nutrients so that your body can use it. Whatever is not needed in your body is being taken care of by the waste system.

. Here are some healthy tips how to keep these networks strong and healthy -
  • Maintain a healthy diet
  • Be consistent with your meals
  • Chew food slowly
  • Drink plenty of water

Conclusion - What is energy system and what is its function? What is waste system and what is its function? Name three healthy ways to keep these systems healthy. Why the waste system is so importnat?


Here are the three worksheets:

Digestive and Excretory systems informational worksheet

Digestive and Excretory systems fill ins worksheet

Digestive system labelling and Digestive process labelling

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