Download Figure 21-16

Digestive Hormones
 Gastrin family
 Gastrin and CCK
 Secretin family
 Secretin, VIP, GIP, and GLP-1
 Others
 Motilin
PLAY Animation: Digestive System: Control of the Digestive System
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
THE DIGESTIVE HORMONES
Hormone
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
Somatostatin
Gastric
Inhibitory
Peptide (GIP)
Endocrine
cells in small
intestine
Beta cells of
endocrine
pancreas
None
Glucose, fatty
acids, and
amino acids in
small intestine
NA
Motilin
Endocrine
cells in small
intestine
Smooth muscle
of antrum and
duodenum
Stimulates migrating
motor complex
Fasting:
periodic release
every 1.5-2
hours by neural
stimulus
NA
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Digestion and Absorption
A villus and a crypt in the small intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-13
Carbohydrate Digestion: Breakdown to
monosaccharide, which can be absorbed
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-14
Carbohydrate Absorption in the Small Intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-15
Enzymes for Protein Digestion
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-16
Peptide Absorption
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-17
Digestion and Absorption
Triglycerides digest into monoglycerides and free fatty
acids
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-18
Digestion and Absorption of Fats
Large fat droplets
from stomach
Bile salts
from liver
1
Emulsion
Bile salts
recycled
Lipase
2
and colipase
Micelles
Lumen of
small intestine
3a
3b
1 Bile salts from liver coat
fat droplets.
2 Pancreatic lipase and
colipase break down
fats into monoglycerides
and fatty acids stored
in micelles.
3a Monoglycerides and
fatty acids move out of
micelles and enter cells
by diffusion.
Smooth
ER
4 Triglycerides + cholesterol + protein
Cells of
small
intestine
Chylomicron
Golgi
apparatus
4 Absorbed fats combine
with cholesterol
and proteins in the
intestinal cells to form
chylomicrons.
5
Interstitial
fluid
Capillary
3b Cholesterol is
transported into cells
by a membrane
transporter.
Lacteal
Lymph
to
vena
cava
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
5 Chylomicrons are
released into the
lymphatic system.
Figure 21-19
Digestion and Absorption
The role of bile salts in emulsions and micelles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-20
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
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Digestion and Absorption
NaCl reabsorption in the small intestine and colon
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-21
Digestion and Absorption
Summary of motility, secretion, digestion, and
absorption in different regions of the digestive system
PLAY Animation: Digestive System: Digestion and Absorption
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-22
3 PHASES OF FOOD PROCESSING
1. Cephalic Phase
2. Gastric Phase
3. Intestinal Phase
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Swallowing Reflex
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-24, step 1
Swallowing Reflex
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-24, step 2
Swallowing Reflex
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-24, step 3
Swallowing Reflex
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-24