1. The Digestive System
Ms. Marcos
Moving into human body systems!

2. What does your digestive system look like?
The tube starts here:
And although there are a few twists and turns along the way…
Anything that goes in the top hole (mouth) does not become part of the body until it is broken down then absorbed though a series of specialized structures.
It comes out here:

3. What does the digestive system do?
DIGESTION:
Mechanical vs. Chemical
ABSORPTION:
Food molecules enter the blood or lymph
Helps you make… ATP!
ELIMINATION:
Wastes / undigested food leave
Large pieces of food to smaller pieces
Enzymes break apart a molecule of food

4. The parts of the digestive system…
Mouth
Tongue
Salivary glands
Oral cavity
Pharynx
Esophagus
Stomach
Pyloric sphincter
Liver
Gall-bladder
Pancreas
Small intestine
Large intestine
Anus
Rectum

5. Many parts work together and are coordinated by hormones.

6. A Tour of the Digestive System
Mouth
Tongue, teeth, salivary glands, pharynx
Enzymes
Esophagus
Epiglottis and choking
Peristalsis
Stomach
Cardiac and pyloric sphincters and stomach cell types
Enzymes and gastric secretions
Pancreas
Digestion enzymes, pH balance and maintenance of blood sugar
Liver / Gall bladder
Roles in digestion and other body processes
Small intestine
Specialization – structure and function three sections and of the villi
Enzyme action
Large intestine
Functions and anaerobic bacteria within
Rectum and Anus
Expulsion of wastes

7. A Tour of the Digestive System

8. The Mouth – Where digestion begins
Hard palate
Soft palate
uvula
Stops liquid or food from coming out your nose when you swallow
Tongue
moves around the food
forms a bolus (a ball of food)

9. Types of teeth
There are different types of teeth for different functions:
Cutting and tearing food
Grinding and mashing food
Crushing and grinding food
Cutting and chopping food

10. What’s in saliva and what does it do?
Water
Makes food soft
Mucus
Helps food slide down the esophagus
Bicarbonate ions
neutralize acid produced by bacteria (helps prevent tooth decay)
Salivary amylase
breaks down starch in the presence of water
Starch  maltose (a disaccharide of glucose)
How much saliva do you produce in a day?
About 1-2 litres!

11. A Tour of the Digestive System

12. A Tour of the Digestive System
Mouth
Tongue, teeth, salivary glands, pharynx
Enzymes
Esophagus
Epiglottis and choking
Peristalsis
Stomach
Cardiac and pyloric sphincters and stomach cell types
Enzymes and gastric secretions
Pancreas
Digestion enzymes, pH balance and maintenance of blood sugar
Liver / Gall bladder
Roles in digestion and other body processes
Small intestine
Specialization – structure and function three sections and of the villi
Enzyme action
Large intestine
Functions and anaerobic bacteria within
Rectum and Anus
Expulsion of wastes

13. Traveling to the stomach…
Esophagus
Tube from pharynx to stomach
Mucus membranes
Helps the food slide down
Muscle
Pushes the food down the tube
Food moves down by peristalsis

14. Peristalsis (and reverse peristalsis)
How long does peristalsis take?
About 9 seconds from pharynx to stomach (rate of 2-4cm/s)
Swallowing Animation

15. Swallowing… Uvula moves back to cover openings to nose
Trachea moves up
Epiglottis covers the trachea
Food goes down by peristalsis

16. Reaching the stomach… Cardiac sphincter
Closes the top of the stomach
Made of muscle
What is heartburn and what causes it?
Opening of the cardiac sphincter allowing food (soaked in stomach acid) to enter the esophagus.

17. A Tour of the Digestive System

18. The Stomach How big is your stomach?
About 1.5 to 2L in an adult human (300L in a cow!)
This is a rabbit stomach

19. The Stomach PEPSIN J-shaped organ Three layers of muscle
Mix up and break up the food
Gastric glands make gastric juice
Gastric juice has:
Pepsinogen + Hydrochloric acid  Pepsin
PEPSIN
an enzyme: proteins  peptides
(small protein sections)

20. Within the walls of the stomach…
Pepsinogen
Pepsin
(Activates more
Pepsinogen)
HCl
Gastric
gland
Mucus cell (shown in red)
Parietal Cell
Peptic cell

21. 3 types of cells in the stomach:
Mucus cells
Mucus protects the stomach
Parietal cells
Secrete acid (HCl at pH 3)
kills bacteria and helps break food down
Peptic cells
Secrete pepsinogen to make pepsin

22. Why doesn’t the stomach digest itself?
HCl could eat through the stomach
Stopped by the mucus layer
Pepsin could digest protein in the stomach cells
Pepsin is only made when pepsinogen mixes with HCl

23. When things go wrong… Bacterial infections Cells can’t make mucus
Can cause ulcers and stomach cancer

24. How long does food stay in your stomach?
2 - 6 hours
Chyme = liquid food that leaves your stomach
Enters the small intestine
controlled by the Pyloric Sphincter
muscle at the bottom of the stomach

25. Digestion Questions #1:
Explain the step by step process that occurs when
someone chokes on a piece of food. What goes wrong? (1)
you are drinking water and accidentally laugh, causing the water to come out of your nose. What goes wrong? (1)
Explain all the types of digestion that occur in the mouth. (2)
What possible problem could lead to an esophageal ulcer? Explain what would happen to cause this. (2)
Explain all the types of digestion that occur in the stomach. (2)
If someone had a severe ulcer, would it be possible to remove his or her stomach and replace it with a bag? What properties would this bag need to have in order to function? How would that person’s diet need to change? (3)