1. The Digestive System
The Physiology

2. Function of the Digestive System
6 processes
Ingestion:
Propulsion
Digestion
Mechanical digestion
Chemical digestion
Absorption
Defecation
These processes occur more or less in order from start to finish (lucky for you!), although the different organs can carry out more than one of these functions

3. Ingestion
Food must be placed in the mouth

4. Propulsion Moving food from one digestive organ to the next Swallowing
Peristalsis
Wave-like contraction and relaxation to move food through a tube

5. Digestion: Mechanical
Mixing of food in the mouth
Tongue and teeth!
Mixing of food in the stomach
Stomach churning
Mixing of food in the small intestine
Segmentation: moving of foodstuff back and forth across the organ walls

6. Digestion: Chemical Enzymes break down foodstuff
Carbohydrates  simple sugars (monosaccharides)
Proteins  amino acids
Fats  fatty acids and glycerides

7. Absorption Digested foods must enter the blood or lymph vessels
Active transport
Passive transport

8. Defecation Elimination of indigestible substances from the body
Feces (poo)

9. Here’s how we are going to play…
From here on out, we are going to go through the passage of food, from mouth to anus, and will connect the functions back to those 6 processes on the previous slide
Get ready!

10. The Mouth Predict: The mouth would perform which of the 6 functions?
Ingestion
That is the food’s first stop!
Propulsion (aka peristalsis)
We have to swallow to move the food to the next organ
Wait….what is the next organ?
The esophagus! 
Mechanical digestion
We masticate our food
Means that we chew it and mix it with saliva using our tongue and teeth
“I was distracted by the half-masticated cow rolling around in your wide-open trap!”
--Miss Congeniality

11. The Mouth Once the food is masticated, it is called a bolus
Chemical digestion
Carbohydrates are broken down
Saliva
Saliva is secreted by salivary glands
Contains an enzyme called salivary amylase
Once the food is masticated, it is called a bolus

12. Esophagus Predict: What functions would the esophagus perform?
Peristalsis
There are layers of smooth muscle to help deliver the bolus to the stomach

13. Stomach Predict the functions Functions
Peristalsis
Has to get the food to the SI
Mechanical digestion
Your stomach churns to further break up the food
Chemical digestion
There are many enzymes that can help break down food
Once the stomach has churned the food, it is called chyme

14. Small Intestine Predict the functions Functions Peristalsis
Mechanical Digestion
Segmentation: mixing food back and forth
Predict the functions
Functions
Peristalsis
Move the food along!
Chemical digestion
Break the macromolecues down further
With the help of:
Pancreas
Digestive enzymes
Liver/gall bladder
Liver produces bile
Bile is stored in the gall bladder
Bile helps to break down fat
Absorption
Nutrients are absorbed so the body can use them
Carbs, proteins, and fats are absorbed

15. Large Intestine Predict the functions Functions Chemical digestion
There are no digestive enzymes in the LI, only bacteria
Absorption
Mostly absorb water
Propulsion
Moving it along!!
Defecation
Poo!

16. Interesting
The bacteria in our large intestines are vital to our survival
Symbiotic relationship (mutualism)
If we ingest too many antibiotics from misuse or a prolonged infection, we can decrease the amount of good bacteria in our colon and can lead to an increase in the bad bacteria
Can lead to colitis (inflammation of colon), constipation, irritable bowel syndrome
Treatment?
Fecal bacteriotherapy
This means that feces from a healthy person is transplanted into the patient
This will transfer that good bacteria into your system
YUM!

17. Let’s make a table ingestion propulsion Mechanical digestion
Chemical digestion
absorption
defecation
Mouth
mouth
Color code the different organs within our GI tract and list them under the correct function. The mouth has been done for you.