1. Digestive Hormones Gastrin family Secretin family Others
Gastrin and CCK
Secretin family
Secretin, VIP, GIP, and GLP-1
Others
Motilin
PLAY
Animation: Digestive System: Control of the Digestive System

2. THE DIGESTIVE HORMONES
Secreted By
Target
Effects on Motility
Stimulus for Release
Release Inhibited by
Gastrin
G cells in stomach
parietal cells
None
Peptides and amino acids in lumen; gastrin releasing peptide and Ach in nervous reflexes
pH<1.5; somatostatin
CCK
Endocrine cells of small intestine; neurons of brain and gut
Gallbladder, pancreas, gastric smooth muscle
Stimulates gallbladder contraction for bile release; inhibits gastric emptying; promotes intestinal motility
Fatty acids and some amino acids
Somatostatin
Secretin
Endocrine cells in small intestine
Pancreas, stomach
Inhibits gastric emptying
Acid in small intestine
Gastric Inhibitory Peptide (GIP)
Beta cells of endocrine pancreas
Glucose, fatty acids, and amino acids in small intestine NA
Motilin
Smooth muscle of antrum and duodenum
Stimulates migrating motor complex
Fasting: periodic release every hours by neural stimulus

3. Digestion and Absorption
A villus and a crypt in the small intestine
Figure 21-13

4. Carbohydrate Digestion: Breakdown to monosaccharide, which can be absorbed
Figure 21-14

5. Carbohydrate Absorption in the Small Intestine
Figure 21-15

6. Enzymes for Protein Digestion
Figure 21-16

7. Peptide Absorption
Figure 21-17

8. Digestion and Absorption
Triglycerides digest into monoglycerides and free fatty acids
Figure 21-18

9. Digestion and Absorption of Fats
Capillary
Cells of
small
intestine
Interstitial
fluid
Triglycerides + cholesterol + protein
Lymph to
vena
cava
Lacteal
Golgi
apparatus
Smooth ER
Chylomicron
Lumen of
small intestine
Large fat droplets
from stomach
Lipase
and colipase
Emulsion
Bile salts
recycled
Micelles
from liver
Monoglycerides and
fatty acids move out of
micelles and enter cells
by diffusion.
Pancreatic lipase and
colipase break down
fats into monoglycerides
and fatty acids stored
in micelles.
Chylomicrons are
released into the
lymphatic system.
Absorbed fats combine
with cholesterol
and proteins in the
intestinal cells to form
chylomicrons.
Bile salts from liver coat
fat droplets.
Cholesterol is
transported into cells
by a membrane
transporter. 1 2 3a 3b 4 5
Figure 21-19

10. Digestion and Absorption
The role of bile salts in emulsions and micelles
Figure 21-20

11. Digestion and Absorption
Nucleic acids are digested into nitrogenous bases and monosaccharides
Intestine absorbs vitamins and minerals
Fat-soluble vitamins (A, D, E, K) absorbed with fats in small intestines
Water-soluble vitamins (C, B vitamins) absorbed by mediated transport
Exception: Vitamin B12 when complexed to intrinsic factor, secreted in the stomach, and absorbed in ileum
Minerals absorbed by active transport

12. Digestion and Absorption
NaCl reabsorption in the small intestine and colon
Figure 21-21

13. Digestion and Absorption
Summary of motility, secretion, digestion, and absorption in different regions of the digestive system
PLAY
Animation: Digestive System: Digestion and Absorption
Figure 21-22

14. 3 PHASES OF FOOD PROCESSING
Cephalic Phase
Gastric Phase
Intestinal Phase

15. The Cephalic Phase
Chemical and mechanical digestion begins in the mouth
Salivary secretion under autonomic control
Softens and lubricates food
Chemical digestion: Salivary amylase and some lipase
Saliva is protection as well
Chewing: mastication

16. Swallowing Reflex
Figure 21-24, step 1

17. Swallowing Reflex
Figure 21-24, step 2

18. Swallowing Reflex
Figure 21-24, step 3

19. Swallowing Reflex
Figure 21-24