the gastric phase
DESCRIPTION
The Gastric Phase. Storage Stomach stores food and controls its passage into the small intestine Digestion Stomach Chemical: Acid, enzymes, and signal molecules Mechanical Protection Stomach acid destroys many bacteria and other pathogens. Stomach protects itself w/thick mucus. - PowerPoint PPT PresentationTRANSCRIPT
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Gastric Phase
Storage Stomach stores food and controls its passage into the
small intestine
Digestion Stomach
Chemical: Acid, enzymes, and signal molecules
Mechanical
Protection Stomach acid destroys many bacteria and other
pathogens. Stomach protects itself w/thick mucus
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-25
The Gastric Phase
Activity of secretory cells of the gastric mucosa
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Gastric Phase
Integration of cephalic and gastric phase secretion in the stomach
Figure 21-26
Lumen ofstomach
Gastric mucosa
Entericplexus
Chiefcell
Gastrin
Somatostatin
Amino acidsor peptides
Input viavagus nerve
Entericsensoryneuron
Entericsensoryneuron
Enterochromaffin-likecell
G cell
D cell
H+
Food
Histamine
Pepsin Pepsinogen
Parietalcell
KEY
Stimulus
Integratingcenter
Receptor
Efferent pathway
Negative feedbackpathway
Food or cephalic reflexes initiate gastric secretion.
Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine.
Acid stimulates short reflexsecretion of pepsinogen.
Somatostatin release by H+
is the negative feedback signalthat modulates acid andpepsin release.
1
2
3
4
1
2
3
4
1
+
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, step 1
The Gastric Phase
Lumen ofstomach
Gastric mucosa
Entericplexus
Gastrin
Amino acidsor peptides
Input viavagus nerve
Entericsensoryneuron
G cell
Food
KEY
Stimulus
Integratingcenter
Receptor
Efferent pathway
Food or cephalic reflexes initiate gastric secretion.
11 1
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, steps 1–2
The Gastric Phase
Lumen ofstomach
Gastric mucosa
Entericplexus
Gastrin
Amino acidsor peptides
Input viavagus nerve
Entericsensoryneuron
ECLcell
G cell
H+
Food
Histamine
Parietalcell
KEY
Stimulus
Integratingcenter
Receptor
Efferent pathway
Food or cephalic reflexes initiate gastric secretion.
Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine.
1
2
1
2
1
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, steps 1–3
The Gastric Phase
Lumen ofstomach
Gastric mucosa
Entericplexus
Chiefcell
Gastrin
Amino acidsor peptides
Input viavagus nerve
Entericsensoryneuron
Entericsensoryneuron
ECLcell
G cell
H+
Food
Histamine
Pepsin Pepsinogen
Parietalcell
KEY
Stimulus
Integratingcenter
Receptor
Efferent pathway
Food or cephalic reflexes initiate gastric secretion.
Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine.
Acid stimulates short reflexsecretion of pepsinogen.
1
2
3
1
2
3
1
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26, steps 1–4
The Gastric Phase
Lumen ofstomach
Gastric mucosa
Entericplexus
Chiefcell
Gastrin
Somatostatin
Amino acidsor peptides
Input viavagus nerve
Entericsensoryneuron
Entericsensoryneuron
ECLcell
G cell
D cell
H+
Food
Histamine
Pepsin Pepsinogen
Parietalcell
KEY
Stimulus
Integratingcenter
Receptor
Efferent pathway
Negative feedbackpathway
Food or cephalic reflexes initiate gastric secretion.
Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine.
Acid stimulates short reflexsecretion of pepsinogen.
Somatostatin release by H+
is the negative feedback signalthat modulates acid andpepsin release.
1
2
3
4
1
2
3
4
1
+
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-27
The Gastric Phase
The mucus-bicarbonate barrier of the gastric mucosa
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-28
The Intestinal Phase
The effects of intestinal-phase events on gastric function
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Intestinal Phase
Bicarbonate neutralizes gastric acid
Goblet cells secrete mucus for protection and lubrication
Bile Fat digestion
Digestive enzymes Enteropeptidase
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-29
Activation of Pancreatic Zymogens
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-30
Hepatic Portal System
Most fluid is absorbed in the small intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Intestinal Phase
Most digestion occurs in small intestine
Large intestine concentrates waste for excretion
Motility in large intestine Mass movement triggers defecation
Defecation reflex
Digestion and absorption in large intestine
Diarrhea can cause dehydration
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31
Anatomy of the Large Intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31a
Anatomy of the Large Intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31b
Anatomy of the Large Intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-31c
Anatomy of the Large Intestine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Immune Function
M cells sample the contents of the gut Immune cells secrete cytokines
Cytokines trigger inflammatory response
Increase in Cl–, fluid, and mucus secretion
Vomiting is a protective reflex
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summary
Function and processes Digestion, absorption, motility, secretion, and GALT
Anatomy
Motility Tonic and phasic contractions
Slow wave potentials, interstitial cells of Cajal, migrating motor complex, peristaltic contractions, and segmental contractions
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summary
Secretion Parietal cells, CFTR chloride channel, mucous cells,
goblet cells, saliva, and bile salts
Regulation Short reflexes, ENS, long reflexes, intrinsic neurons,
gastrin family, secretin family, and other hormones
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summary
Digestion and absorption Amylase, disaccharidases, endopeptidases,
exopeptidases, lipase, colipase, micelles, chylomicrons, and intrinsic factor
The cephalic phase
The gastric phase Mucous cells, chief cells, D cells, ECL cells, and G
cells
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Summary
The intestinal phase Brush border, mass movement, and defecation reflex
Immune functions M cells and vomiting