© 2014 Pearson Education, Inc. Figure 22.17 Neural and hormonal mechanisms that regulate release of gastric juice. Stimulatory events Inhibitory events Cephalic phase Sight and thought of food 1 Cerebral cortex Lack of stimulatory impulses to parasym- pathetic center Cerebral cortex Loss of appetite, depression 1 Conditioned reflex Stimulation of taste and smell receptors 2 Hypothalamus and medulla oblongata Vagus nerve Stomach distension activates stretch receptors 1 Vagovagal reflexes Medulla Vagus nerve Gastrin secretion declines G cells Excessive acidity (pH < 2) in stomach 1 Gastric phase Local reflexes Overrides parasym- pathetic controls Sympathetic nervous system activation Emotional stress 2 Food chemicals (especially peptides and caffeine) and rising pH activate chemoreceptors 2 G cells Gastrin release to blood Stomach secretory activity Entero- gastric reflex Local reflexes Distension of duodenum; presence of fatty, acidic, or hypertonic chyme; and/or irritants in the duodenum 1 Presence of partially digested foods in duodenum or distension of the duodenum when stomach begins to empty 1 Intestinal (enteric) gastrin release to blood Vagal nuclei in medulla Brief effect Intestinal phase Pyloric sphincter Release of enterogastrones (secretin, cholecystokinin, vasoactive intestinal peptide) Distension; presence of fatty, acidic, partially digested food in the duodenum 2 Stimulate Inhibit © 2014 Pearson Education, Inc.

© 2014 Pearson Education, Inc. Figure 22.17 Neural and hormonal mechanisms that regulate release of gastric juice. Stimulatory events Inhibitory events Cephalic phase Sight and thought of food 1 Cerebral cortex Lack of stimulatory impulses to parasym- pathetic center Cerebral cortex Loss of appetite, depression 1 Conditioned reflex Stimulation of taste and smell receptors 2 Hypothalamus and medulla oblongata Vagus nerve Stomach distension activates stretch receptors 1 Vagovagal reflexes Medulla Vagus nerve Gastrin secretion declines G cells Excessive acidity (pH < 2) in stomach 1 Gastric phase Local reflexes Overrides parasym- pathetic controls Sympathetic nervous system activation Emotional stress 2 Food chemicals (especially peptides and caffeine) and rising pH activate chemoreceptors 2 G cells Gastrin release to blood Stomach secretory activity Entero- gastric reflex Local reflexes Distension of duodenum; presence of fatty, acidic, or hypertonic chyme; and/or irritants in the duodenum 1 Presence of partially digested foods in duodenum or distension of the duodenum when stomach begins to empty 1 Intestinal (enteric) gastrin release to blood Vagal nuclei in medulla Brief effect Intestinal phase Pyloric sphincter Release of enterogastrones (secretin, cholecystokinin, vasoactive intestinal peptide) Distension; presence of fatty, acidic, partially digested food in the duodenum 2 Stimulate Inhibit © 2014 Pearson Education, Inc.

Figure 22.15b Microscopic anatomy of the stomach. Gastric pits Surface epithelium (mucous cells) Gastric pit Mucous neck cells Parietal cell Gastric gland Chief cell Enteroendocrine cell Enlarged view of gastric pits and gastric glands © 2014 Pearson Education, Inc.

Figure 22.15c Microscopic anatomy of the stomach. Pepsinogen Pepsin HCI Mitochondria Parietal cell Chief cell Enteroendocrine cell Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland © 2014 Pearson Education, Inc.

Figure 22.18 Mechanism of HCl secretion by parietal cells. Gastric gland Blood capillary Chief cell Stomach lumen CO2 CO2 + H2O H+-K+ ATPase Carbonic anhydrase H2CO3 H+ H+ K+ K+ HCO3− HCI Alkaline tide Parietal cell HCO3− Cl− Cl− Cl− HCO3−- Cl− antiporter Interstitial fluid © 2014 Pearson Education, Inc.

Figure 22.15c Microscopic anatomy of the stomach. Pepsinogen Pepsin HCI Mitochondria Parietal cell Chief cell Enteroendocrine cell Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland © 2014 Pearson Education, Inc.

Bacteria Mucosa layer of stomach A gastric ulcer lesion Figure 22.16 Photographs of a gastric ulcer and the H. pylori bacteria that most commonly cause it. Bacteria Mucosa layer of stomach A gastric ulcer lesion H. pylori bacteria © 2014 Pearson Education, Inc.

© 2014 Pearson Education, Inc. Figure 22.17 Neural and hormonal mechanisms that regulate release of gastric juice. Stimulatory events Inhibitory events Cephalic phase Sight and thought of food 1 Cerebral cortex Lack of stimulatory impulses to parasym- pathetic center Cerebral cortex Loss of appetite, depression 1 Conditioned reflex Stimulation of taste and smell receptors 2 Hypothalamus and medulla oblongata Vagus nerve Stomach distension activates stretch receptors 1 Vagovagal reflexes Medulla Vagus nerve Gastrin secretion declines G cells Excessive acidity (pH < 2) in stomach 1 Gastric phase Local reflexes Overrides parasym- pathetic controls Sympathetic nervous system activation Emotional stress 2 Food chemicals (especially peptides and caffeine) and rising pH activate chemoreceptors 2 G cells Gastrin release to blood Stomach secretory activity Entero- gastric reflex Local reflexes Distension of duodenum; presence of fatty, acidic, or hypertonic chyme; and/or irritants in the duodenum 1 Presence of partially digested foods in duodenum or distension of the duodenum when stomach begins to empty 1 Intestinal (enteric) gastrin release to blood Vagal nuclei in medulla Brief effect Intestinal phase Pyloric sphincter Release of enterogastrones (secretin, cholecystokinin, vasoactive intestinal peptide) Distension; presence of fatty, acidic, partially digested food in the duodenum 2 Stimulate Inhibit © 2014 Pearson Education, Inc.

Figure 22.14a Anatomy of the stomach. Cardia Fundus Esophagus Muscularis externa Serosa Longitudinal layer Circular layer Oblique layer Body Lumen Lesser curvature Rugae of mucosa Greater curvature Pyloric sphincter (valve) at pylorus Pyloric canal Pyloric antrum Duodenum © 2014 Pearson Education, Inc.

Figure 22.19 Peristaltic waves in the stomach. Pyloric valve slightly opened Pyloric valve closed Pyloric valve closed Propulsion: Peristaltic waves move from the fundus toward the pylorus. 1 Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus. 2 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. 3 © 2014 Pearson Education, Inc.

Figure 22.30c Mesenteries of the abdominal digestive organs. Greater omentum Transverse colon Transverse mesocolon Descending colon Jejunum Mesentery Sigmoid mesocolon Sigmoid colon Ileum © 2014 Pearson Education, Inc.

Vein carrying blood to hepatic portal vessel Muscle layers Lumen Figure 22.22a Structural modifications of the small intestine that increase its surface area for digestion and absorption. Vein carrying blood to hepatic portal vessel Muscle layers Lumen Circular folds Villi © 2014 Pearson Education, Inc.

Microvilli (brush border) Absorptive cells Lacteal Villus Goblet cell Figure 22.22b Structural modifications of the small intestine that increase its surface area for digestion and absorption. Microvilli (brush border) Absorptive cells Lacteal Villus Goblet cell Blood capillaries Mucosa- associated lymphoid tissue Intestinal crypt Enteroendocrine cells Venule Muscularis mucosae Lymphatic vessel Duodenal gland Submucosa © 2014 Pearson Education, Inc.

Absorptive cells Goblet cells Villi Intestinal crypt Figure 22.22c Structural modifications of the small intestine that increase its surface area for digestion and absorption. Absorptive cells Goblet cells Villi © 2014 Pearson Education, Inc. Intestinal crypt

Figure 22.21 The duodenum of the small intestine, and related organs. Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Tail of pancreas Pancreas Gallbladder Jejunum Major duodenal papilla Main pancreatic duct and sphincter Hepatopancreatic ampulla and sphincter Duodenum Head of pancreas © 2014 Pearson Education, Inc.

Chyme enter -ing duodenum causes duodenal Figure 22.28 Mechanisms promoting secretion and release of bile and pancreatic juice. Chyme enter -ing duodenum causes duodenal enteroendocrine cells to release cholecystokinin (CCK) and secretin. 1 4 Bile salts and, to a lesser extent, secretin transported via bloodstream stimulate Liver to produce bile more rapidly. 5 CCK (via blood stream) causes gallbladder to contract and Hepatopancreatic Sphincter to relax. Bile Enters duodenum. CCK (red dots) and secretin (yellow dots) enter the bloodstream. 2 CCK induces secretion of enzyme-rich pancreatic juice. Secretin causes secretion of HCO3− -rich pancreatic juice. 3 During cephalic and gastric phases, vagal Nerve stimu- lates gallbladder to contract weakly. 6 CCK secretion Secretin secretion © 2014 Pearson Education, Inc.

Figure 22.29a Gross anatomy of the large intestine. Left colic (splenic) flexure Transverse mesocolon Right colic (hepatic) flexure Epiploic appendages Transverse colon Superior mesenteric artery Descending colon Haustrum Ascending colon IIeum Cut edge of mesentery IIeocecal valve Tenia coli Sigmoid colon Cecum Appendix Rectum Anal canal External anal sphincter © 2014 Pearson Education, Inc.

Figure 22.29b Gross anatomy of the large intestine. Rectal valve Rectum Hemorrhoidal veins Levator ani muscle Anal canal External anal sphincter Internal anal sphincter Anal columns Pectinate line Anal sinuses Anus © 2014 Pearson Education, Inc.

Figure 22.31 Defecation reflex. Impulses from cerebral cortex (conscious control) Sensory nerve fibers Feces move into and distend the rectum, stimulating stretch receptors there. The receptors transmit signals along afferent fibers to spinal cord neurons. 1 Voluntary motor nerve to external anal sphincter Sigmoid colon Stretch receptors in wall A spinal reflex is initiated in which parasympathetic motor (efferent) fibers stimulate contraction of the rectum and sigmoid colon, and relaxation of the internal anal sphincter. 2 Rectum External anal sphincter (skeletal muscle) Involuntary motor nerve (parasympathetic division) Internal anal sphincter (smooth muscle) If it is convenient to defecate, voluntary motor neurons are inhibited, allowing the external anal sphincter to relax so feces may pass. 3 © 2014 Pearson Education, Inc.