1. Digestive System

2. Functions 1. Breaks down the food so that the body can use it
2. Molecules are absorbed in the blood and carried throughout the body
3. Solid wastes are eliminated from the body

4. An overview of the process

5. Digestive Process
Begins

6. 4 Processes of Digestion
Ingestion: Getting food into our bodies
Digestion: Breaking down food into smaller nutrients
Absorption: Getting those nutrients into our bloodstream, so that our cells can use them
Elimination: Getting rid of solid waste products
Eat it!
Break it Down!
Soak It Up!
Go to the Bathroom!

7. 2 Types of Digestion
Digestion means breaking down food into smaller particles, called nutrients
There are 2 kinds of digestion
Mechanical: Food is broken down by physical processes (chewing, grinding, moving etc.)
AND
Chemical: Food is broken down by chemicals (saliva and acids)

8. What are nutrients?
Nutrients are things that our bodies need to survive:
Water = H2O
Proteins
Carbohydrates
Fats
Vitamins
Minerals

9. Mouth
Functions:
Mechanically breaks down food by chewing
Wets the food with saliva
Chemically breaks down food with enzymes in saliva

10. Saliva Saliva-fluid that is released to help break down food
chemical digestion- enzymes in saliva mechanical digestion- soften the bolus for easier swallowing

11. Teeth
Digestion starts here. The job of the teeth is to start tearing and crushing the food down into small enough pieces so that it can fit down our throats.

12. Epiglottis
Epiglottis- A flap called the epiglottis closes over the top of the trachea (windpipe) when swallowing, so that food does not enter the respiratory tract
Mucus helps food go down easier

13. Esophagus
Functions:
Involuntary smooth muscles contract and push food toward the stomach

14. Peristalsis
The walls of the digestive tract from the esophagus to the anus are muscular, and contract rhythmically to move food. The muscular contractions are called peristalsis

15. Stomach
Functions:
The lining releases digestive juice, which contains:
Pepsin- Enzyme that breaks down protein
Hydrochloric Acid (HCl) - Strong Acid to kill any bacteria you may have ingested
Thick stomach muscles create a churning motion to mechanically digest food
What type of internal stimulus causes vomiting?

16. What’s that sound?
Stomach growling occurs when the stomach receives signals from your brain to begin digestion but the stomach is empty.
Your brain might sense you're running low on energy or even seeing or smelling something you want to eat can get things going.
The motion of the stomach muscles begins, but the organ is hollow.
The movement of the muscles mixing the acids of the stomach in the hollow space of the stomach produces vibrations we hear as growling, or rumbling, or gurgling.
Picture from:
* Dogs eat grass when they feel nauseated. They want to throw up, because they have learned that they feel better afterwards.
*See slide note

17. Pancreas Attached near the first part of the small intestine
Produces enzymes that help breaks down starches, fat and proteins that goes into the small intestines
Does not break down fiber

18. Liver and Gallbladder LIVER:
Breaks down medicines, other substances and helps break down nitrogen
Produces Bile- breaks up fat particles into small droplets
Gallbladder-stores the bile
After you eat the bile passes through a tube from the gallbladder into the small intestine.

19. Small Intestine Functions:
Peristalsis (contraction and relaxation of muscles) to push the food through
Chemical Digestion through enzymes
Absorption of nutrients to the blood

20. Blood
Functions:
Blood Vessels are found within the villi of the small intestine, here they absorb nutrients and deliver to the entire body

21. Drying Out and Exiting the Body
By the time the food that was eaten leaves the small intestine, most of the usable nutrients have been digested and absorbed.
The remaining undigested material moves into the large intestine where large amounts of water are removed and the final undigested wastes exit the body through the rectum (stored waste material) and anus (comes out).
The large intestines also contain large amounts of bacteria (some sources say over 700 types!) that digest some of the remaining material and produce certain vitamins.
These bacteria also produce GAS as a by product!
Rectum
Anus
Large Intestine
Appendix
Picture of girl from:
Digestive system images from Servier Medical Art:
So that’s where it comes from!

22. Fun Digestive Facts:
On average, the stomach produces liters of Hydrochloric Acid daily.
After you eat, it takes usually between 24 and 72 hours in healthy adults for the complete process of digestion to occur.
In the mouth, food is either cooled or warmed to a more suitable temperature.
Food stays in your stomach for 2 to 3 hours.
The average male will eat about 50 tons of food during his lifetime in order to sustain a weight of 150 pounds.

23. More Fun Digestive Facts
The liver is the largest and heaviest internal organ of the body and weighs about 1.6 kilos.
The Liver is the only organ of the body, which has the capacity to regenerate itself completely even after being removed almost completely.
Scientists estimate that the average adult releases between 12 and 122 cubic inches of intestinal gas each day. Most of that gas is made up of hydrogen and methane produced by the bacteria as they ferment the fiber that was not digested in the stomach or small intestine.