1. The Digestive System
SNC2D

2. Phases of Digestion Mechanical (physical) Phases Include Chemical
Chew
Tear
Grind
Mash
Mix
Chemical
Enzymatic reactions to improve digestion of
Carbohydrates
Proteins
Lipids
Phases Include
Ingestion
Movement
Mechanical and Chemical Digestion
Absorption
Elimination

3. The Digestive Tract The Digestive tract is…
a series of hollow organs which may be thought of as a long twisting tube connecting the mouth to the anus, and other organs that produce or store chemicals that help break down or absorb food.

4. The Mouth
Digestion begins in the mouth where an enzyme (a chemical that speeds up other chemical reactions) in the saliva produced by the salivary glands start to break down those carbohydrates known as starches. This enzyme is called amylase.

5. The Mouth Cont’d
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 muscle movement 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. Peristalsis
Once the food is swallowed, it is moved through the digestive tract by peristalsis, involuntary muscle contractions triggered by the nervous system.

8. To The Stomach
Food travels down the esophagus to the stomach. Between the esophagus and the stomach there is a muscle called the lower esophageal sphincter, which opens to let food pass through. If it opens when it shouldn't’t, you get acid reflux (heartburn).

9. In the Stomach
Glands in the stomach lining produce stomach acid and an enzyme to break down proteins. A thick layer of mucus helps protect the lining of the stomach from its own acids.
Bacterial infections can thin the mucus so that the stomach eats away at its own lining: this is an ulcer.

10. 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 and lipids.
Acid in the stomach kills bacteria.
Food found in the stomach is called chyme.
Muscle action of the stomach mixes the food with the digestive juices, and this mixture is then emptied into the small intestine through the pyloric sphincter.
The stomach takes around 4 hours to do it’s job on the food, depending on what kinds of food are digested.

11. The Small Intestine
The first part of the small intestine, where the chemicals produced by the other organs enter the digestive process, is called the duodenum. Nutrients from the food pass into the blood stream through the small intestine walls. Absorbs : - 80 % of ingested water - Vitamins - Minerals - Carbs - Proteins - Lipids

12. The Small Intestine
The small intestine is roughly 7 meters long, folded into fingerlike projections called villi. This folding increases the surface area of the small intestine through which food molecules are absorbed into the bloodstream. Villi are covered in microvilli which further increases surface area for absorption!

13. The Large Intestine (colon)
Is about 5 ft long, accepts what small intestine don’t absorb
Functions include
- bacterial digestion (fermenting carbohydrates and protein breakdown )
Absorption of water
Concentrating Wastes

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

15. Liver Directly affects digestion by producing bile
Bile helps digest fat
filters out toxins and waste including drugs and alcohol
Livers can regenerate missing pieces if necessary. Is one of the largest organs in the body.

16. 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.

17. Pancreas
Produces digestive enzymes to digest fats, carbohydrates and proteins
Regulates blood sugar by producing insulin
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.

18. The Body’s Defences
The digestive system’s first defence against contaminants is vomiting, which can forcibly remove contents from the middle of the small intestine and up.
Really, you don’t want any images here.

19. 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!!