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Transcript of © 2014 Pearson Education, Inc. Figure 22.17 Neural and hormonal mechanisms that regulate release of...
© 2014 Pearson Education, Inc.
Figure 22.17 Neural and hormonal mechanisms that regulate release of gastric juice.
Lack ofstimulatoryimpulses toparasym-patheticcenter
Gastrinsecretiondeclines
Overridesparasym-patheticcontrols
Sympatheticnervoussystemactivation
Cerebralcortex
G cells
Emotionalstress
Excessiveacidity(pH < 2)in stomach
Loss ofappetite,depression
Entero-gastricreflex
Localreflexes
Pyloricsphincter
Vagalnucleiin medulla
Distensionof duodenum;presence offatty, acidic, orhypertonicchyme; and/orirritants inthe duodenum
Release ofenterogastrones(secretin, cholecystokinin,vasoactive intestinalpeptide)
Distension;presence offatty, acidic,partiallydigested foodin theduodenum
Intestinal(enteric)gastrinreleaseto blood
Briefeffect
Gastrinreleaseto blood
Vagusnerve
Vagusnerve
Conditioned reflex
Localreflexes
Vagovagalreflexes
G cells
Presence ofpartially digested foods in duodenumor distension of theduodenum when stomach begins to empty
Stimulate
Inhibit
Hypothalamusand medullaoblongata
Cerebral cortex
Medulla Stomachdistensionactivatesstretchreceptors
Food chemicals(especially peptides andcaffeine) and rising pHactivate chemoreceptors
Stimulation oftaste and smellreceptors
Sight and thoughtof food
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Stimulatory events Inhibitory events
Cephalicphase
Gastricphase
Intestinalphase
Stomachsecretoryactivity
© 2014 Pearson Education, Inc.
Figure 22.17 Neural and hormonal mechanisms that regulate release of gastric juice.
Lack ofstimulatoryimpulses toparasym-patheticcenter
Gastrinsecretiondeclines
Overridesparasym-patheticcontrols
Sympatheticnervoussystemactivation
Cerebralcortex
G cells
Emotionalstress
Excessiveacidity(pH < 2)in stomach
Loss ofappetite,depression
Entero-gastricreflex
Localreflexes
Pyloricsphincter
Vagalnucleiin medulla
Distensionof duodenum;presence offatty, acidic, orhypertonicchyme; and/orirritants inthe duodenum
Release ofenterogastrones(secretin, cholecystokinin,vasoactive intestinalpeptide)
Distension;presence offatty, acidic,partiallydigested foodin theduodenum
Intestinal(enteric)gastrinreleaseto blood
Briefeffect
Gastrinreleaseto blood
Vagusnerve
Vagusnerve
Conditioned reflex
Localreflexes
Vagovagalreflexes
G cells
Presence ofpartially digested foods in duodenumor distension of theduodenum when stomach begins to empty
Stimulate
Inhibit
Hypothalamusand medullaoblongata
Cerebral cortex
Medulla Stomachdistensionactivatesstretchreceptors
Food chemicals(especially peptides andcaffeine) and rising pHactivate chemoreceptors
Stimulation oftaste and smellreceptors
Sight and thoughtof food
1
1
2
1
2
1
2
1
2
1
Stimulatory events Inhibitory events
Cephalicphase
Gastricphase
Intestinalphase
Stomachsecretoryactivity
© 2014 Pearson Education, Inc.
Figure 22.15b Microscopic anatomy of the stomach.
Enteroendocrine cell
Enlarged view of gastric pits andgastric glands
Chief cell
Parietal cell
Mucous neck cells
Surface epithelium (mucous cells)
Gastric pits
Gastricpit
Gastricgland
© 2014 Pearson Education, Inc.
Figure 22.15c Microscopic anatomy of the stomach.
Mitochondria
Parietal cell
Chief cell
Enteroendocrine cell
Location of the HCl-producing parietal cellsand pepsin-secreting chief cells in a gastricgland
HCIPepsinPepsinogen
© 2014 Pearson Education, Inc.
Figure 22.18 Mechanism of HCl secretion by parietal cells.
HCIParietal cell
Interstitialfluid
HCO3−- Cl−
antiporter
Alkalinetide
H+-K+
ATPase
Stomach lumenChief cell
Gastric gland
H+
K+
CO2 CO2 H2O
H2CO3
+
HCO3−
H+
K+
Carbonicanhydrase
HCO3−
Bloodcapillary
Cl− Cl− Cl−
© 2014 Pearson Education, Inc.
Figure 22.15c Microscopic anatomy of the stomach.
Mitochondria
Parietal cell
Chief cell
Enteroendocrine cell
Location of the HCl-producing parietal cellsand pepsin-secreting chief cells in a gastricgland
HCIPepsinPepsinogen
© 2014 Pearson Education, Inc.
Figure 22.16 Photographs of a gastric ulcer and the H. pylori bacteria that most commonly cause it.
A gastric ulcer lesion H. pylori bacteria
Bacteria
Mucosalayer ofstomach
© 2014 Pearson Education, Inc.
Figure 22.17 Neural and hormonal mechanisms that regulate release of gastric juice.
Lack ofstimulatoryimpulses toparasym-patheticcenter
Gastrinsecretiondeclines
Overridesparasym-patheticcontrols
Sympatheticnervoussystemactivation
Cerebralcortex
G cells
Emotionalstress
Excessiveacidity(pH < 2)in stomach
Loss ofappetite,depression
Entero-gastricreflex
Localreflexes
Pyloricsphincter
Vagalnucleiin medulla
Distensionof duodenum;presence offatty, acidic, orhypertonicchyme; and/orirritants inthe duodenum
Release ofenterogastrones(secretin, cholecystokinin,vasoactive intestinalpeptide)
Distension;presence offatty, acidic,partiallydigested foodin theduodenum
Intestinal(enteric)gastrinreleaseto blood
Briefeffect
Gastrinreleaseto blood
Vagusnerve
Vagusnerve
Conditioned reflex
Localreflexes
Vagovagalreflexes
G cells
Presence ofpartially digested foods in duodenumor distension of theduodenum when stomach begins to empty
Stimulate
Inhibit
Hypothalamusand medullaoblongata
Cerebral cortex
Medulla Stomachdistensionactivatesstretchreceptors
Food chemicals(especially peptides andcaffeine) and rising pHactivate chemoreceptors
Stimulation oftaste and smellreceptors
Sight and thoughtof food
1
1
2
1
2
1
2
1
2
1
Stimulatory events Inhibitory events
Cephalicphase
Gastricphase
Intestinalphase
Stomachsecretoryactivity
© 2014 Pearson Education, Inc.
Figure 22.14a Anatomy of the stomach.Cardia
EsophagusMuscularisexterna
Lessercurvature
DuodenumPyloric sphincter(valve) at pylorus
Pyloriccanal
Pyloricantrum
Greatercurvature
Rugae ofmucosa
Lumen
Body
Serosa
Fundus
• Oblique layer• Circular layer• Longitudinal layer
© 2014 Pearson Education, Inc.
Figure 22.19 Peristaltic waves in the stomach.
Pyloricvalveclosed
Pyloricvalveslightlyopened
Pyloricvalveclosed
Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus.
Retropulsion: The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum, simultaneously forcing most of its contained material backward into the stomach.
2 Propulsion: Peristaltic waves move from the fundus toward the pylorus.
1 3
© 2014 Pearson Education, Inc.
Greater omentum
Transverse colon
Transversemesocolon
Descending colon
MesenterySigmoid mesocolon
Jejunum
Sigmoid colon
Ileum
Figure 22.30c Mesenteries of the abdominal digestive organs.
© 2014 Pearson Education, Inc.
Figure 22.22a Structural modifications of the small intestine that increase its surface area for digestion and absorption.
Vein carryingblood tohepatic portalvessel
Musclelayers
Circularfolds
Villi
Lumen
© 2014 Pearson Education, Inc.
Figure 22.22b Structural modifications of the small intestine that increase its surface area for digestion and absorption.Microvilli(brush border)
Absorptivecells
VillusLacteal
GobletcellBloodcapillariesMucosa-associatedlymphoidtissueIntestinalcryptMuscularismucosae
Duodenalgland
Enteroendocrinecells
VenuleLymphatic vessel
Submucosa
© 2014 Pearson Education, Inc.
Figure 22.22c Structural modifications of the small intestine that increase its surface area for digestion and absorption.
Gobletcells
Absorptive cells
Villi
Intestinal crypt
© 2014 Pearson Education, Inc.
Figure 22.21 The duodenum of the small intestine, and related organs.
Right and left hepatic ducts of liver
Common hepatic ductBile duct and sphincterAccessory pancreatic duct
Tail of pancreasPancreasJejunum
Main pancreatic duct and sphincter
Head of pancreasHepatopancreaticampulla and sphincter Duodenum
Mucosawith folds
Gallbladder
Major duodenalpapilla
Cystic duct
© 2014 Pearson Education, Inc.
Chyme enter-ing duodenum causes duodenalenteroendocrine cells to release cholecystokinin(CCK) and secretin.
CCK (red dots) andsecretin (yellow dots) enter the bloodstream.
CCK inducessecretion of enzyme-richpancreatic juice. Secretin causes secretion of HCO3
− -rich pancreatic juice.
Bile salts and, to a lesser extent, secretintransported viabloodstream stimulate Liver to produce bile more rapidly.
CCK (via blood stream) causes gallbladder to contract and HepatopancreaticSphincter to relax. Bile Enters duodenum.
During cephalicand gastric phases,vagal Nerve stimu-lates gallbladder tocontract weakly.
CCK secretion
Secretin secretion
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Figure 22.28 Mechanisms promoting secretion and release of bile and pancreatic juice.
© 2014 Pearson Education, Inc.
Figure 22.29a Gross anatomy of the large intestine.
Right colic(hepatic) flexure
Transverse colon
Superiormesenteric artery
Ascending colonIIeum
IIeocecal valve
Cecum
Appendix
Left colic(splenic) flexureTransversemesocolon
Epiploicappendages
Descending colon
Cut edge ofmesenteryTenia coli
Sigmoid colon
RectumAnal canal External anal sphincter
Haustrum
© 2014 Pearson Education, Inc.
Figure 22.29b Gross anatomy of the large intestine.
Rectal valveRectumHemorrhoidalveins
Levator ani muscle
Anal canal
External analsphincterInternal analsphincterAnal columnsPectinate lineAnal sinuses
Anus
© 2014 Pearson Education, Inc.
Figure 22.31 Defecation reflex.
Impulses fromcerebral cortex(consciouscontrol)
Voluntary motornerve to externalanal sphincter
External analsphincter(skeletal muscle)
Sensorynerve fibers
Sigmoidcolon
Stretch receptors in wall
Involuntary motor nerve (parasympathetic division)Internal anal sphincter (smooth muscle)
Feces move into anddistend the rectum,stimulating stretch receptorsthere. The receptors transmitsignals along afferent fibersto spinal cord neurons.
A spinal reflex is initiated in whichparasympathetic motor (efferent) fibersstimulate contraction of the rectum andsigmoid colon, and relaxation of theinternal anal sphincter.
If it is convenient to defecate,voluntary motor neurons are inhibited,allowing the external anal sphincter to relax so feces may pass.
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Rectum