1. Digestive System
[Day 1]
Note: can do the crackers etc demo

2. Main Ideas
Mouth  stomach

3. 1. Mouth
Starting point!
Saliva – lubricates food & esophagus; moistens food
Mechanical Digestion – when teeth cut & grind food into smaller pieces
Chemical Digestion – salivary amalase begins to breakdown starch into maltose

4. 1. Mouth

5. Swallowing
Tongue rolls food into ball (“bolus”) – moves to back of pharynx
Soft palate closes off nasopharynx; epiglottis covers opening to
trachea
My Swallow Study(1).mp4
Swallowing (deglutition) from Anatomy _ Physiology Online.mp4

6. 2. Esophagus Once food enters, peristalsis begins
Muscle contractions, move bolus to stomach
“do the wave” 

7. 3. Stomach Esophagus  cardiac sphincter  stomach
Sphincter = muscular ring; valve
Prevents back flow!
Esophagus
Cardiac Sphincter
Duodenum
Stomach
Pyloric Sphincter

8. 3. Stomach

9. 3. Stomach Bolus mixes with gastric juices  “chyme”
Lining of stomach has gastric pits
Secrete gastric juices
Has pepsin, HCl, mucus
Pepsin: enzyme to breakdown proteins
HCl: kill pathogens; convert pepsinogen to pepsin
Mucus: protect stomach lining from chem. digestion
Pepsin = chemical digestion
HCl – kills bacteria/pathogens; converts pepsinogen to pepsin
Mucus – protects walls from acid and pepsin

10. 3. Stomach Gastrin Hormone Stimulates secretion of HCl
Triggered by high protein meals

11. Ulcers
Helicobacter pylori – helix shaped; literally screw itself into stomach lining to colonize
Infects mucosal linings – prevents mucus production
No mucus – hole!
REALLY common! [2/3 population has colony?]; only when populations increase enough do you have symptoms
may be asymptomatic for long time
becoming antibiotic resistance [b/c common treatment]
Spicy foods often increase uclers  reduces lining b/c more acidic  make H. pylori’s job easier

12. Ulcers Mucus normally is replaced every few days Helicobacter pylori
Bacteria, infects mucus lining of stomach
Thrives in highly acidic environment!
If no/low mucus  acid & pepsin start to break down stomach!

13. To Do’s Questions [next slide]
Provincial questions!! #5, 9, 17, 19, 20, 23, 25, 27, 28, 30, 44
Dictionary
Mechanical digestion; chemical digestion; bolus; chyme; peristalsis; sphincter; gastric juices; ulcer
Q’s?

14. Questions Why is saliva important?
Why do the epiglotis and nasopharynx need to close before swallowing?
Why are sphincters important?
Why is it important the esophagus is soft and flexible, unlike the trachea?
Where do we find bolus? Chyme? How are they different?