1. Chapter 17 Digestive System
Functions of Digestive System
ingestion
mechanical digestion
chemical digestion
propulsion
absorption
defecation
17-2

2. Major Organs
17-3

3. Alimentary Canal
17-4

4. Alimentary Canal Wall
17-5

5. Movements of the Tube
mixing movements
peristalsis
17-6

6. 1. Mouth ingestion mechanical digestion
prepares food for chemical digestion
17-8

7. Palate
roof of oral cavity
17-10

8. Primary Teeth
8 incisors
4 cuspids
8 molars
17-11

9. Secondary Teeth
17-12

10. 2. Salivary Glands
17-14

11. Secretions of Salivary Glands
Parotid glands
clear
water, serous fluid
rich in amylase
Sublingual glands
primarily mucus
most viscous
Submandibular glands
primarily serous fluid
some mucus
17-15

12. Swallowing Mechanism soft palate and uvula raise
hyoid bone and larynx elevate
epiglottis closes off top of trachea
longitudinal muscles of pharynx contract
inferior constrictor muscles relax and esophagus opens
peristaltic waves push food through pharynx
17-17

13. 3. Esophagus
17-19

14. 4. Stomach
17-20

15. Lining of Stomach
17-22

16. Gastric Secretions pepsinogen from chief cells inactive form of pepsin
mucus
from goblet cells and mucous glands
protective to stomach wall
pepsin
from pepsinogen in presence of HCl
protein splitting enzyme
intrinsic factor
from parietal cells
required for vitamin B12 absorption
hydrochloric acid
from parietal cells
needed to convert pepsinogen to pepsin
17-23

17. Phases of Gastric Secretion
Cephalic phase
triggered by smell, taste, sight, or thought of food
parasympathetic impulses trigger gastric juice secretion
Gastric phase
triggered by presence of food in stomach
gastrin released
gastric juice secreted
Intestinal phase
triggered by movement of food into small intestine
intestinal cells release intestinal gastrin
secretion of gastric juice
17-24

18. Gastric Absorption some water certain salts
certain lipid-soluble drugs
alcohol
17-26

19. Mixing and Emptying Actions
17-27

20. 5. Three Parts of Small Intestine
17-39

21. Mesentery
suspends portions of the small intestine from the posterior abdominal wall
17-40

22. Intestinal Villus
17-41

23. Wall of Small Intestine
17-43

24. Secretions of Small Intestine
peptidase – breaks down peptides into amino acids
sucrase, maltase, lactase – break down disaccharides into monosaccharides
lipase – breaks down fats into fatty acids and glycerol
enterokinase – converts trypsinogen to trypsin
somatostatin – hormone that inhibits acid secretion by stomach
cholecystokinin – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, stimulates gallbladder to release bile
secretin – stimulates pancreas to release bicarbonate ions in pancreatic juice
17-44

25. Regulation of Small Intestinal Secretions
mucus secretion stimulated by presence of chyme in small intestine
distension of intestinal wall activates nerve plexuses in wall of small intestine
parasympathetics trigger release of intestinal enzymes
17-45

26. Absorption in the Small Intestine
monosaccharides and amino acids
through facilitated diffusion and active transport
absorbed into blood
electrolytes and water
through diffusion, osmosis, and active transport
absorbed into blood
17-46

27. Absorption in the Small Intestine
fatty acids and glycerol
several steps
absorbed into lymph and blood
17-47

28. Movements of the Small Intestine
mixing movements
peristalsis – pushing movements
segmentation – ringlike contractions
overdistended wall triggers peristaltic rush resulting in diarrhea
17-48

29. 6. Large Intestine
17-49

30. Functions of Large Intestine
little or no digestive function
absorbs water and electrolytes
secretes mucus
houses intestinal flora
forms feces
carries out defecation
17-51

31. Movements of Large Intestine
slower and less frequent than those of small intestine
mixing movements
peristalsis
mass movements usually follow meals
17-52

32. Feces water electrolytes mucus bacteria
bile pigments altered by bacteria provide color
smell produced by bacterial compounds
17-53