1. The Human Digestive System

2. Digestion Phases Include Ingestion Mechanical and Chemical Digestion
Absorption
Elimination

3. Digestion
Types
Mechanical (physical): increase surface area to increase rate of enzyme action
Chew
Tear
Grind
Mash
Mix
Chemical: Enzymatic reactions to that change
Carbohydrates into simple sugars
Proteins into amino acids
Lipids into fatty acids and glycerol

4. Digestive System Organization
Gastrointestinal (Gl) tract
Tube within a tube
Direct link/path between organs
Structures
Mouth
Esophagus/Epiglottis
Stomach
Small intestine
Large Intestine
Rectum

5. Mouth
Teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch).
Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.

6. Esophagus Approximately 10” long Functions include: Secrete mucus
Moves food from the throat to the stomach using muscular contractions called peristalsis
If acid from the stomach gets in here that’s heartburn.
A good way to describe peristalsis is an ocean wave moving through the muscle.
These diagrams don’t separate the esophagus from the mouth functions, you might want to talk about what happens in the mouth too.

7. Stomach
J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces.
Mixes food with digestive juices that contain enzymes to break down proteins (protease.)
Hydrochloric Acid (HCl) in the stomach kills bacteria and dissolves bone.
Food found in the stomach is called chyme.
The stomach takes around 4 hours to do it’s job on the food, depending on what kinds of food are digested.

8. Small Intestine Small intestines are roughly 7 meters long
Digestion ends here (carbs, proteins, and lipids are all digested)
Accessory organs (liver, pancreas, gall bladder) secrete enzymes, etc. into small intestine to complete carb, protein, and lipid digestion)
Lining of intestine walls has finger-like projections called villi, to increase surface area for absorption into the bloodstream.

9. 9/14/2018

10. Small Intestine
Nutrients from the food pass into the bloodstream through the small intestine walls.
Absorbs:
80% ingested water
Vitamins
Minerals
Carbohydrates
Proteins
Lipids
(Bile, Tripeptidase, dipeptidase,
Lipase, pancreatic amylase)

11. Large Intestine About 5 feet long
Accepts what small intestines don’t absorb
Rectum (short term storage which holds feces before it is expelled).
Depending on the maturity of the group, you can talk about the feces leaving via the anus.
Mention the appendix at the bottom of the ascending colon and that it might have been used long ago but is not today
Mention the portions of the large intestine, ascending, transverse, descending, sigmoid, and rectum (last one if the audience is mature enough)

12. Large Intestine Functions
Bacterial digest some waste producing valuable vitamins
Absorbs more water
Concentrate (dehydrate) wastes

13. Accessory Organs
Not part of the path of food, but play a critical role in digestion .
Include: Liver, gall bladder, and pancreas

14. Liver Directly affects digestion by producing bile
Bile helps digest fat
Emulsifies fats into globules that can be digested by lipases
Detoxifies the blood by filtering out poisons like drugs and alcohol
Recycles dead or damaged red blood cells
Stores extra glucose as glycogen
Deamination of amino acids – body can’t store amino acids so the liver breaks them down into their component parts, creating the nitrogenous waste, urea
Livers can regenerate missing pieces if necessary. Is one of the largest organs in the body.

15. Gall Bladder
Stores bile from the liver, releases it into the small intestine.
Fatty diets can cause gallstones
Explain to students that removing the stones typically means removing the gallbladder, but that the body eventually adjusts to not having the bile stored.

16. Pancreas Digestive JOB: Regulatory JOB:
Produces digestive enzymes to digest fats (lipases), carbohydrates (pancreatic amylase) and proteins (tri- & di- peptidases)
Regulatory JOB:
Regulates blood sugar by producing insulin and glucagon
Explain the difference between the two types of diabetes. In type 1, the pancreas fails to produce enough insulin. In type 2, the body stops responding properly to the insulin it creates.

17. Fun Facts
HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long!
Food drying up and hanging out in the large intestine can last 18 hours to 2 days!
In your lifetime, your digestive system may handle about 50 tons!!

18. Now it's...
QUIZ TIME!

19. On a sheet of paper, write the name of each colored organ:
Green:
Red:
Pink:
Brown:
Purple:
Yellow:

20. How’d you do? Green: Esophagus Red: Stomach Pink: Small Intestine
Brown: Large Intestine
Purple: Liver
Green: Gall Bladder
Yellow: Pancreas
Great Job!

21. References and Links Your Digestive System and How It Works
Digestive system diagram comes from this site
The Real Deal on the Digestive System
Pancreas: Introduction and Index
Your Gross and Cool Body - Digestive System