1. The Digestive System

2. The gastrointestinal tract (GI) is also called the alimentary canal.

3. 8 Major Activities
1. Ingestion - The intake of food into the digestive tract through the mouth.
2. Mechanical processing – Chewing and mixing of food along the digestive tract.

4. 8 Major Activities
3. Digestion – Chemical breakdown of food into its building blocks.
4. Secretion – release of water, acids, enzymes, and buffers by digestive cells.

5. 8 Major Activities
Absorption – movement of small organic molecules into bloodstream.
Defecation – formation and removal of feces (waste)

6. 8 Major Activities Defense – high acidity, enzymes & macrophages.
Peristalsis – the involuntary, sequential contractions of smooth muscle tissue that moves food along the tract.

7. Organs of the digestive system

8. Anatomy of the Oral Cavity: Mouth
Figure 23.7a

9. Oral Cavity and Pharynx: Anterior View
Figure 23.7b

10. The lingual frenulum holds the tongue to the floor of the mouth.
Children born with extremely short lingual frenulums are often referred to as tongue-tied because of speech distortions that occur.

11. Usually 32 permanent teeth, but sometimes wisdom teeth never erupt.

12. Salivary Glands
Figure 23.9a

13. Peristalsis is the involuntary movement of food through the digestive system.
Figure 14.3A
Slide 14.4
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

14. Motility: Segmentation
Figure 14.3B
Slide 14.5
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

15. Stomach
Figure 23.14a

16. Liver The largest gland in the body
Superficially has four lobes – right, left, caudate, and quadrate
The falciform ligament:
Separates the right and left lobes anteriorly
Suspends the liver from the diaphragm and anterior abdominal wall

17. Liver Functions
Production of bile, which is stored in the gall bladder
Storage of fat-soluble vitamins and glycogen, which can be changed into sugar if our blood sugar levels fall
Detoxification

18. Composition of Bile
A yellow-green, alkaline solution containing bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes
Bile salts are cholesterol derivatives that:
Emulsify fat
Facilitate fat and cholesterol absorption
Help solubilize cholesterol
The chief bile pigment is bilirubin, a waste product of heme

19. Gallbladder and Associated Ducts
Figure 23.20

20. Gall Bladder Removal
When the gall bladder is removed, the duct from the liver is directly connected to the small intestine.
The bile is then less concentrated.

21. Gall Stones
When a person eats a lot of fat, cholesterol can form on calcium crystals in the gall bladder, creating stones – sometimes in the hundreds!!

22. Gall Stones

23. Painless unless they block a duct.
A stone trapped in the neck of the gall bladder causes acute cholecystitis.
In severe cases, the gall bladder explodes from pressure of the blockage.

24. The small intestine is the major absorptive site.

28. Large Intestine
Figure 14.12
Slide 14.13A