1. The Human Digestive System
What do you already know?
Complete the Digestive System Handout to the best of your ability without looking in any text or your notes.
You may work in groups.
Do not complete the bottom overview.

2. The Human Digestive System
Video Overview

3. Why do we need a Digestive System?
When you eat foods such as bread, meat, and vegetables, they are not in a form that the body can use. Food and drink consumed must be broken down into smaller molecules so that they can be absorbed into the body.

4. Components of the Digestive System?
The Digestive Tract is a series of hollow organs joined in a long, twisted tube from the mouth to the anus.
Organs involved:
Mouth
Esophagus
Stomach
Liver
Pancreas
Small Intestine
Large Intestine
Rectum
Oral Cavity (mouth)
Esophagus
Small Intestine

5. Components of the Digestive System?
The entire length of the digestive tract is lined with epithelial tissue.
Contains lots of goblet cells which secrete mucus. The mucus does two things
Protects tract from digestive enzymes
Moves materials along the tube

6. Digestive Enzymes
Digestive Enzymes help to break food into smaller pieces so that it is easier to digest
Digestive Enzymes Video

7. The Mouth
Digestion begins in the oral cavity (mouth) where 2 types of digestion take place:
Mechanical Digestion
Chemical Digestion

8. Mechanical Digestion
Chewing breaks up large pieces of food into smaller ones

9. Chemical Digestion
The Human Body releases 1 – 1.5L of saliva per day from glands in your cheeks (salivary glands)
Saliva converts Carbohydrates into simple sugars like Glucose.
Glucose

10. Chemical Digestion
Saliva also contains mucus and water which makes food easier to swallow.

11. Digestion Activity
Obtain: 2 Saltine Crackers
1 Napkin

12. Digestion Activity – Part 1
Copy, complete and answer the following.
Put 1 regular cracker into your mouth and chew slowly.
What was the texture like?
How did it feel while you were chewing it?
What did it taste like?
Sweet? Plain? Record your observations.

13. Digestion Activity Part 2 – Record your observations
Place a cracker in your mouth and let it sit for 1.5 min. before chewing
What it feels like initially in your mouth
- Is it sweet/bland?
What is feels like after 1 min. in your mouth
What it feels like after 1.5 min. in your mouth
What it feels like when you chew it after 1.5 min.

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These digital clock timers countdown from either 2 minutes, 1 min 30secs or 1 minute. The timings of these cannot be easily changed, although the colour can be by simply selecting the entire ‘pile’ of shapes that makes them up, and then formatting the colours.
There is a bell timer at the end of the countdown, if this is not desired then enter the animation settings, and delete the animation that ends .wav from the animation listing.

15. Chewing Crackers Discussion
What was the main texture (feeling) difference in your mouth between chewing right away and waiting 1.5 minutes before chowing down?
What does your saliva do to the cracker?
When the cracker is in your mouth your saliva starts to break it down  get’s softer

16. Grab a ruler and have a look
Esophagus
Food enters the esophagus which is a narrow, muscular tube about 25 centimeters long.
Food is swallowed by voluntary action (you control) of the tongue.
Grab a ruler and have a look

17. Esophagus
The Trachea (Wind Pipe) and Esophagus are connected: – Why does food not go into lungs?
There is a small flap consisting of connective tissue which prevents food from entering the trachea when swallowing (Epiglottis).
Trachea

18. Esophagus
The wall of the esophagus is made up of two layers of smooth muscles which push the food down into the stomach
If a person were to swallow while being upside down you could see the muscles in action.

19. Demo Place your hand over your throat then swallow - What do you feel?
2) Turn to someone next to you.
Have your partner tilt their head up
Watch their neck as they swallow – reverse roles

20. Stomach
The stomach acts as a storage place for food as well as a place
of digestion.
It is also described as an elastic “bag” made
of muscle which expands.
- It can hold up to 4 L of food!!

21. Stomach Chemical Digestion:
Stomach cells produce acid (HCl) which helps break down proteins
The stomach cells also secrete mucus to protect its lining from the acid.
Sometimes this acid exits the stomach and enter the esophagus
Can lead to heart burn - Video

22. Stomach
Mechanical Digestion: The muscles of the stomach wall contract and expand to churn food and move it towards the small intestine.
The growling sound you sometimes here is your stomach moving.
This is smooth muscle

23. Bread in bag experiment:
Step 1:
Get ½ slice of bread and a small sandwich bag from the front of the room.

24. Bread in bag experiment:
Step 2:
Tear your ½ slice of bread into smaller pieces and place it into your sandwich bag
(What does this represent?)

25. Bread in bag experiment:
Step 3:
Raise your hand once step 2 is completed and your teacher will come around now and pour a small amount of liquid into the bag.

26. Bread in bag experiment:
Step 4:
Close your bag (make sure it is sealed well) and squish/knead the bread with your fingers until all of the pieces are really small
(What does this represent?)

27. Bread in bag experiment:
Step 5: Over the trash can cut the corner off of the bottom of the bag and let the contents run out into the garbage. (What does this represent?)

28. Small Intestine
The small intestine further splits food into smaller pieces. Most of the nutrients we take in are absorbed in the small intestine.
Blood
Small Intestine Video

29. Small Intestine
Receives many digestive enzymes from the pancreas and liver to help break down food
Moves food using smooth muscle cell contraction
The lining of the intestine secretes protective mucus to protect it from the enzymes
Is about 7 m (22 feet 6 inches) long, 2.5 cm (1 inch) in diameter and has a surface area of 250 square meters (2,700 square feet) – the size of a tennis court!

30. Large Intestine Sometimes called the Colon.
Its function is to absorb water and vitamins from the remaining food.
Also stores the remains of the food that cannot be absorbed (wastes) before they are flushed from the body.
About 1.5 m (5 feet) long and 6.5 cm (2.5 inches) in diameter
Called the large intestine because it has a much larger diameter than the small intestine

31. Rectum
The rectum acts as a temporary storage facility for feces before it is excreted from the body.
Uranus

32. Accessory Organs
The Liver, Pancreas, and Gall Bladder all help with the digestion by supplying digestive enzymes.
The Liver also produces bile which helps digest fats
These substances are delivered into the Small Intestine

33. Liver Produces bile which is stored in the gall bladder.
Bile is then sent to the small intestine to break down fats.
Gall Bladder

34. Pancreas
Is involved in supplying enzymes required for digestion directly into the small intestine.
Secretes a hormone called insulin directly into the blood stream.
Insulin causes most of the body's cells to take up circulating glucose (cell food) from the blood.
If insulin is not used effectively, diabetes can result.
Insulin Video

35. Review and Revisit Name that Digestive System Organ 1) Liver
2) Esophagus
3) Stomach
4) Pancreas
5) Small Intestine
6) Large Intestine
7) Rectum 1 2 3 4 5 6 7

36. The Human Digestive System Handout Revisited
What do you already know?
Complete the Digestive System Handout to the best of your ability without looking in any text or your notes.
Complete the bottom section using information from this Power Point

37. Excellent Digestive System Interactive Activities – Please Click to Visit