1. Digestive System Anatomy and Function Functions
Convert food into smaller molecules that can be absorbed by cells
Remove solid waste
B. 2 Major components
1. The Alimentary Canal (your food tube)
2. Digestive glands
How does digestion relate to cellular respiration?

2. Digestive System II. The Alimentary Canal
Mouth – Two types of digestion
Mechanical digestion – Tear & crush food (chewing)
Chemical digestion
Saliva – produced by salivary glands, moisten food making it easier to chew
Contains amylase (breaks down carbs) and lysozyme (kills bacteria)
Release of saliva is triggered by the nervous system by the scent of food. Amylase breaks the chemical bonds in starches and releases sugar, which is why if you eat a cracker long enough, it will start to taste sweet. Lysozymes fight infection by digesting the cell wall of many bacteria.

3. Digestive System Pharynx (throat) Connects mouth to esophagus
Swallow chewed up food ball called a bolus
Epiglottis covers the trachea – Why?
Epiglottis

4. Digestive System Esophagus
Moves food to the stomach by peristalsis (Fig )
Cardiac Sphincter
Thick ring of muscle that closes the esophagus after food enters the stomach.
Why is this important?
Heartburn
What causes it?
Gravity is not the cause for food traveling to stomach; wave of contraction push food down

5. Digestive System Stomach
Food mixes with hydrochloric acid (HCl) and pepsin to form chyme.
Stomach can hold up to 2 L of food or liquid. HCl kills bacteria and disrupts the extracelliular matrix that binds cells in meat and plants.

6. Digestive System HCl activates pepsin
Pepsin breaks down large protein molecules into small chains of ????
Stomach can hold up to 2 L of food or liquid. HCl kills bacteria and disrupts the extracelliular matrix that binds cells in meat and plants.
What protects the stomach from pepsin and HCl?

7. What is pyloric stenosis?
Digestive System
After 1-2 hours, pyloric valve opens and chyme flows into the small intestine.
What is pyloric stenosis?

8. Digestive System F. Small Intestine Duodenum (~ 1 foot long)
This is where most of your food is digested and absorbed
3 Sections:
Duodenum (~ 1 foot long)
Digestive enzymes from the pancreas and the liver are added to the food.
The gall bladder adds bile
The pancreas adds sodium bicarbonate is also added…WHY?
10 feet long

9. Digestive System Jejunum (~ 3 feet) and Ileum (~ 6 feet)
The inside of the intestine is not smooth but has many small folds called villi and the villi have many microscopic folds called microvilli.
Why all of the folds?
Once absorbed, how do nutrients get to cells?
Villi
Microvilli

10. Where is your appendix?
Appendix

11. Digestive System Large Intestine (Colon)
Reabsorbs water from undigested material
What happens when too much water is absorbed? Too little?
Bacteria in colon produce Vitamin K and live off undigested organic material (e.g. E. coli)
Bacteria generate gases (methane and hydrogen sulfide) as a by-product of their metabolism 
Remaining undigested material (feces) is excreted through the rectum and anus
5 feet long. Vit K controls blood clotting

12. Large Intestine (Colon)

13. Alimentary Canal (Gastrointestinal “GI” Tract)
1. Mouth
2. Pharynx
3. Esophagus
4. Stomach
6. Large Intestine
5. Small Intestine
7. Rectum

14. Accessory Organs Glands 10. Liver 9. Pancreas (behind stomach)
8. Salivary
Glands
10. Liver
9. Pancreas (behind stomach)
11. Gall Bladder

15. III. Digestive Glands Liver Detoxifies the blood
Stores vitamins and minerals
Converts foodstuffs from one form to another
Produces bile
Bile contains no digestive enzymes, but it has salts which help digest fats. Bile also contains pigments that are by products of RBC destruction in the liver.

16. III. Digestive Glands (cont)
Gall Bladder
1. Stores and releases bile
2. Bile emulsifies fats
Pancreas
Produces ???? And ????
Digestion Recap…