1. Unit 2: Cells and Systems
Topic 3: The Digestive System

2. Different Systems Interact!

3. Digestive System Remember the main factors of life?
All organisms require energy to survive
Obtain energy from:
Carbohydrates (sugars and starches)

4. Digestive System Remember the main factors of life?
All organisms require energy to survive
Obtain energy from
Carbohydrates (sugars and starches)
Lipids (fats and oils)

5. Digestive System Remember the main factors of life?
All organisms require energy to survive
Obtain energy from
Carbohydrates (sugars and starches)
Lipids (fats and oils)
Proteins (Steak, burgers)

6. Types of Digestion Mechanical Digestion
The physical breakdown of food into small pieces

7. Types of Digestion Mechanical Digestion Chemical Digestion
The physical breakdown of food into small pieces
Chemical Digestion
Large particles are broken down by a objects called Enzymes*
*molecules created by cells whose job it is to break down objects. Similar to how an acid can dissolve something!

8. Types of Digestion Place the Soda Cracker in your mouth and chew it.
You are breaking it down into smaller pieces
That is Mechanical digestion
Place a new Soda Cracker in your mouth and leave it there, DO NOT CHEW.
Perhaps you notice it getting softer, breaking down and perhaps starting to taste a little sweeter?
The enzyme Amylase in your saliva is breaking down the starch molecules in the Soda Cracker into smaller Sugar molecules
This is Chemical digestion

9. Journey Through the Digestive System
Lets follow the journey of our favourite couple Mr. and Mrs. Potato head, and his journey of DESTRUCTION…….I mean safe passage…..through the digestive tract.

10. Journey Through the Digestive System
We begin at the mouth
Food is mechanically broken down by chewing
Salivary glands in the mouth produce saliva to soften the food for safe passage through the digestive system

11. Journey Through the Digestive System
We begin at the mouth
Food is mechanically broken down by chewing
Salivary glands in the mouth produce saliva to soften the food for safe passage through the digestive system
Saliva contains the enzyme amylase! It can digest starch molecules!
Hey look honey, it is amylase, surely as STARCH potatoes we will be just fine!

12. Journey Through the Digestive System
Humans have three salivary glands!

13. Journey Through the Digestive System
Next, your tongue pushes the food….I mean Mr. and Mrs. Potato head to the back of your mouth.
The epiglottis (a flap of skin) covers your windpipe and directs Mr. and Mrs. Potato head down your esophagus.
They travel down through a process called Peristalsis
This means muscles contract to squeeze an object down. Similar to how you get the last bit of toothpaste out!

14. Journey Through the Digestive System
Next, your tongue pushes the food….I mean Mr. and Mrs. Potato head to the back of your mouth.
The epiglottis (a flap of skin) covers your windpipe and directs Mr. and Mrs. Potato head down your esophagus.
They travel down through a process called Peristalsis
This means muscles contract to squeeze an object down. Similar to how you get the last bit of toothpaste out!
Wow, I feel pretty slimy and I taste pretty sweet right now. Something seems odd about this trip!
And the Esophagus slide is squeezing me down so tight and uncomfortably.

15. Epiglottis

16. Swallowing

17. Journey Through the Digestive System
As the Food (Mr. and Mrs. Potato head) travel to the stomach, they are a Stimulus.
The stomach responds and mixes the food with Gastric Juice.
Gastric Juice is made of mucus, hydrochloric acid and enzymes which work together to break down food
Mucus protects the stomach from digesting itself!
The entrance and exit of a Stomach is gated with a Sphincter, basically a door in or out.

18. Sphincter

19. Journey Through the Digestive System
As the Food (Mr. and Mrs. Potato head) travel to the stomach, they are a Stimulus.
The stomach responds and mixes the food with Gastric Juice.
Gastric Juice is made of mucus, hydrochloric acid and enzymes which work together to break down food
Mucus protects the stomach from digesting itself!
OMG OMG OMG we are dissolving!!!!!!! What kind of a trip is this!!!!!!???????

20. Journey Through the Digestive System
The food from the stomach is now liquid and passes into the small intestine.
Chemical digestion happens here too!
The Liver now plays a role
A small compartment called the Gall Bladder releases Bile into the intestines to further digest lipids.

21. Journey Through the Digestive System
The small intestine has Villi
Tiny hair like structures everywhere
They increase surface area and absorb nutrients into the body
If the villi was stretched out with your intestine, it would have enough surface area to cover the whole floor in the classroom!
If villi wasn’t enough for you, there are microvilli on the villi!

22. Journey Through the Digestive System

23. Journey Through the Digestive System
Wow Honey, you look really different, I feel so squishy…… that was one heck of a ride!
Uh ohhhh, I feel rumbling, maybe this is the exit????
Now we enter the Large Intestine.
The Large intestine most importantly absorbs water here back into your body
The large intestine absorbs the remaining vitamins and minerals not absorbed by the small intestine.
What is left is feces! Something monkeys really like to toss at each other!

24. The End of the Journey

25. Cool Science Fact
Some guy named Alexis St. Martin had hole in his left side that led directly to his stomach.
So naturally Dr. William Beaumont wanted to stick stuff in the hole and see what happened.
He dangled food to see how the stomach would digest it!

26. Cool Science Fact
Scientists estimate that Gut Bacteria ranges in number from the same about of cells you have in your body, up to ten times that!
It has a pretty science name: GUT FLORA