1. Pharynx From the mouth, the oro- and laryngopharynx allow passage of: From the mouth, the oro- and laryngopharynx allow passage of: Food and fluids to the esophagus Food and fluids to the esophagus Air to the trachea Air to the trachea Lined with stratified squamous epithelium and mucus glands Lined with stratified squamous epithelium and mucus glands Has two skeletal muscle layers Has two skeletal muscle layers Inner longitudinal Inner longitudinal Outer pharyngeal constrictors Outer pharyngeal constrictors

2. Esophagus Muscular tube going from the laryngopharynx to the stomach Muscular tube going from the laryngopharynx to the stomach Travels through the mediastinum and pierces the diaphragm Travels through the mediastinum and pierces the diaphragm Joins the stomach at the cardiac orifice Joins the stomach at the cardiac orifice

3. Esophageal Characteristics Esophageal mucosa – nonkeratinized stratified squamous epithelium Esophageal mucosa – nonkeratinized stratified squamous epithelium The empty esophagus is folded longitudinally and flattens when food is present The empty esophagus is folded longitudinally and flattens when food is present Glands secrete mucus as a bolus (compacted food product) moves through the esophagus Glands secrete mucus as a bolus (compacted food product) moves through the esophagus Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly) Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly)

4. Digestive Processes in the Mouth Food is ingested Food is ingested Mechanical digestion begins (chewing) Mechanical digestion begins (chewing) Propulsion is initiated by swallowing Propulsion is initiated by swallowing Salivary amylase begins chemical breakdown of starch Salivary amylase begins chemical breakdown of starch The pharynx and esophagus serve as conduits to pass food from the mouth to the stomach The pharynx and esophagus serve as conduits to pass food from the mouth to the stomach

5. Deglutition (Swallowing) Coordinated activity of the tongue, soft palate, pharynx, esophagus, and 22 separate muscle groups Coordinated activity of the tongue, soft palate, pharynx, esophagus, and 22 separate muscle groups Buccal phase – bolus is forced into the oropharynx Buccal phase – bolus is forced into the oropharynx

6. Deglutition (Swallowing) Pharyngeal-esophageal phase – controlled by the medulla and lower pons All routes except into the digestive tract are sealed off All routes except into the digestive tract are sealed off Peristalsis moves food through the pharynx to the esophagus Peristalsis moves food through the pharynx to the esophagus

7. Stomach Chemical breakdown of proteins begins and food is converted to chyme Chemical breakdown of proteins begins and food is converted to chyme Cardiac region – surrounds the cardiac orifice Cardiac region – surrounds the cardiac orifice Fundus – dome-shaped region beneath the diaphragm Fundus – dome-shaped region beneath the diaphragm Body – midportion of the stomach Body – midportion of the stomach Pyloric region – made up of the antrum and canal which terminates at the pylorus Pyloric region – made up of the antrum and canal which terminates at the pylorus The pylorus is continuous with the duodenum through the pyloric sphincter The pylorus is continuous with the duodenum through the pyloric sphincter

8. Stomach Greater curvature – entire extent of the convex lateral surface Greater curvature – entire extent of the convex lateral surface Lesser curvature – concave medial surface Lesser curvature – concave medial surface Lesser omentum – runs from the liver to the lesser curvature Lesser omentum – runs from the liver to the lesser curvature Greater omentum – drapes inferiorly from the greater curvature to the small intestine Greater omentum – drapes inferiorly from the greater curvature to the small intestine

9. Stomach Nerve supply – sympathetic and parasympathetic fibers of the autonomic nervous system Nerve supply – sympathetic and parasympathetic fibers of the autonomic nervous system Blood supply – celiac trunk, and corresponding veins (part of the hepatic portal system) Blood supply – celiac trunk, and corresponding veins (part of the hepatic portal system)

10. Microscopic Anatomy of the Stomach Muscularis – has an additional oblique layer that: Muscularis – has an additional oblique layer that: Allows the stomach to churn, mix, and pummel food physically Allows the stomach to churn, mix, and pummel food physically Breaks down food into smaller fragments Breaks down food into smaller fragments

11. Microscopic Anatomy of the Stomach Epithelial lining is composed of: Epithelial lining is composed of: Goblet cells that produce a coat of alkaline mucus Goblet cells that produce a coat of alkaline mucus The mucous surface layer traps a bicarbonate-rich fluid beneath it The mucous surface layer traps a bicarbonate-rich fluid beneath it Gastric pits contain gastric glands that secrete gastric juice, mucus, and gastrin Gastric pits contain gastric glands that secrete gastric juice, mucus, and gastrin

12. Glands of the Stomach Fundus and Body Gastric glands of the fundus and body have a variety of secretory cells Gastric glands of the fundus and body have a variety of secretory cells Mucous neck cells – secrete acid mucus Mucous neck cells – secrete acid mucus Parietal cells – secrete HCl and intrinsic factor Parietal cells – secrete HCl and intrinsic factor

13. Glands of the Stomach Fundus and Body Chief cells – produce pepsinogen Chief cells – produce pepsinogen Pepsinogen is activated to pepsin by: Pepsinogen is activated to pepsin by: HCl in the stomach HCl in the stomach Pepsin itself via a positive feedback mechanism Pepsin itself via a positive feedback mechanism Enteroendocrine cells – secrete gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and somatostatin into the lamina propria Enteroendocrine cells – secrete gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and somatostatin into the lamina propria

14. Stomach Lining The stomach is exposed to the harshest conditions in the digestive tract The stomach is exposed to the harshest conditions in the digestive tract To keep from digesting itself, the stomach has a mucosal barrier with: To keep from digesting itself, the stomach has a mucosal barrier with: A thick coat of bicarbonate-rich mucus on the stomach wall A thick coat of bicarbonate-rich mucus on the stomach wall Epithelial cells that are joined by tight junctions Epithelial cells that are joined by tight junctions Gastric glands that have cells impermeable to HCl Gastric glands that have cells impermeable to HCl Damaged epithelial cells are quickly replaced Damaged epithelial cells are quickly replaced

15. Digestion in the Stomach The stomach: The stomach: Holds ingested food Holds ingested food Degrades this food both physically and chemically Degrades this food both physically and chemically Delivers chyme to the small intestine Delivers chyme to the small intestine Enzymatically digests proteins with pepsin Enzymatically digests proteins with pepsin Secretes intrinsic factor required for absorption of vitamin B 12 Secretes intrinsic factor required for absorption of vitamin B 12

16. Regulation of Gastric Secretion Neural and hormonal mechanisms regulate the release of gastric juice Neural and hormonal mechanisms regulate the release of gastric juice Stimulatory and inhibitory events occur in three phases Stimulatory and inhibitory events occur in three phases Cephalic (reflex) phase: prior to food entry Cephalic (reflex) phase: prior to food entry Gastric phase: once food enters the stomach Gastric phase: once food enters the stomach Intestinal phase: as partially digested food enters the duodenum Intestinal phase: as partially digested food enters the duodenum

17. Cephalic Phase Excitatory events include: Excitatory events include: Sight or thought of food Sight or thought of food Stimulation of taste or smell receptors Stimulation of taste or smell receptors Inhibitory events include: Inhibitory events include: Loss of appetite or depression Loss of appetite or depression Decrease in stimulation of the parasympathetic division Decrease in stimulation of the parasympathetic division

18. Gastric Phase Excitatory events include: Excitatory events include: Stomach distension Stomach distension Activation of stretch receptors (neural activation) Activation of stretch receptors (neural activation) Activation of chemoreceptors by peptides, caffeine, and rising pH Activation of chemoreceptors by peptides, caffeine, and rising pH Release of gastrin to the blood Release of gastrin to the blood

19. Gastric Phase Inhibitory events include: Inhibitory events include: A pH lower than 2 A pH lower than 2 Emotional upset that overrides the parasympathetic division Emotional upset that overrides the parasympathetic division

20. Intestinal Phase Excitatory phase – low pH; partially digested food enters the duodenum and encourages gastric gland activity Excitatory phase – low pH; partially digested food enters the duodenum and encourages gastric gland activity Inhibitory phase – distension of duodenum, presence of fatty, acidic, or hypertonic chyme, and/or irritants in the duodenum Inhibitory phase – distension of duodenum, presence of fatty, acidic, or hypertonic chyme, and/or irritants in the duodenum Initiates inhibition of local reflexes and vagal nuclei Initiates inhibition of local reflexes and vagal nuclei Closes the pyloric sphincter Closes the pyloric sphincter Releases enterogastrones that inhibit gastric secretion Releases enterogastrones that inhibit gastric secretion

21. Regulation and Mechanism of HCl Secretion HCl secretion is stimulated by ACh, histamine, and gastrin through second-messenger systems HCl secretion is stimulated by ACh, histamine, and gastrin through second-messenger systems Antihistamines block H 2 receptors and decrease HCl release Antihistamines block H 2 receptors and decrease HCl release

22. Response of the Stomach to Filling Stomach pressure remains constant until about 1L of food is ingested Stomach pressure remains constant until about 1L of food is ingested Relative unchanging pressure results from reflex-mediated relaxation and plasticity Relative unchanging pressure results from reflex-mediated relaxation and plasticity

23. Response of the Stomach to Filling Reflex-mediated events include: Reflex-mediated events include: Receptive relaxation – as food travels in the esophagus, stomach muscles relax Receptive relaxation – as food travels in the esophagus, stomach muscles relax Adaptive relaxation – the stomach dilates in response to gastric filling Adaptive relaxation – the stomach dilates in response to gastric filling Plasticity – intrinsic ability of smooth muscle to exhibit the stress-relaxation response Plasticity – intrinsic ability of smooth muscle to exhibit the stress-relaxation response

24. Gastric Contractile Activity Peristaltic waves move toward the pylorus at the rate of 3 per minute Peristaltic waves move toward the pylorus at the rate of 3 per minute This basic electrical rhythm (BER) is initiated by pacemaker cells (cells of Cajal) This basic electrical rhythm (BER) is initiated by pacemaker cells (cells of Cajal)

25. Gastric Contractile Activity Most vigorous peristalsis and mixing occurs near the pylorus Most vigorous peristalsis and mixing occurs near the pylorus Chyme is either: Chyme is either: Delivered in small amounts to the duodenum or Delivered in small amounts to the duodenum or Forced backward into the stomach for further mixing Forced backward into the stomach for further mixing

26. Regulation of Gastric Emptying Gastric emptying is regulated by: Gastric emptying is regulated by: The neural enterogastric reflex The neural enterogastric reflex Hormonal (enterogastrone) mechanisms Hormonal (enterogastrone) mechanisms These mechanisms inhibit gastric secretion and duodenal filling These mechanisms inhibit gastric secretion and duodenal filling

27. Regulation of Gastric Emptying Carbohydrate-rich chyme quickly moves through the duodenum Carbohydrate-rich chyme quickly moves through the duodenum Fat-laden chyme is digested more slowly causing food to remain in the stomach longer Fat-laden chyme is digested more slowly causing food to remain in the stomach longer

28. Small Intestine: Gross Anatomy Runs from pyloric sphincter to the ileocecal valve Runs from pyloric sphincter to the ileocecal valve Has three subdivisions: duodenum, jejunum, and ileum Has three subdivisions: duodenum, jejunum, and ileum

29. Small Intestine: Gross Anatomy The bile duct and main pancreatic duct: The bile duct and main pancreatic duct: Join the duodenum at the hepatopancreatic ampulla Join the duodenum at the hepatopancreatic ampulla Are controlled by the sphincter of Oddi Are controlled by the sphincter of Oddi The jejunum extends from the duodenum to the ileum The jejunum extends from the duodenum to the ileum The ileum joins the large intestine at the ileocecal valve The ileum joins the large intestine at the ileocecal valve

30. Small Intestine: Microscopic Anatomy Structural modifications of the small intestine wall increase surface area Structural modifications of the small intestine wall increase surface area Plicae circulares: deep circular folds of the mucosa and submucosa Plicae circulares: deep circular folds of the mucosa and submucosa Villi – fingerlike extensions of the mucosa Villi – fingerlike extensions of the mucosa Microvilli – tiny projections of absorptive mucosal cells’ plasma membranes Microvilli – tiny projections of absorptive mucosal cells’ plasma membranes

31. Small Intestine: Histology of the Wall The epithelium of the mucosa is made up of: The epithelium of the mucosa is made up of: Absorptive cells and goblet cells Absorptive cells and goblet cells Enteroendocrine cells Enteroendocrine cells Interspersed T cells called intraepithelial lymphocytes (IELs) Interspersed T cells called intraepithelial lymphocytes (IELs) IELs release cytokines IELs release cytokines

32. Small Intestine: Histology of the Wall Cells of intestinal crypts secrete intestinal juice Cells of intestinal crypts secrete intestinal juice Peyer’s patches are found in the submucosa Peyer’s patches are found in the submucosa Brunner’s glands in the duodenum secrete alkaline mucus Brunner’s glands in the duodenum secrete alkaline mucus

33. Intestinal Juice Secreted by intestinal glands in response to distension or irritation of the mucosa Secreted by intestinal glands in response to distension or irritation of the mucosa Slightly alkaline and isotonic with blood plasma Slightly alkaline and isotonic with blood plasma Largely water, enzyme-poor, but contains mucus Largely water, enzyme-poor, but contains mucus

34. Liver The largest gland in the body The largest gland in the body Superficially has four lobes – right, left, caudate, and quadrate Superficially has four lobes – right, left, caudate, and quadrate The falciform ligament: The falciform ligament: Separates the right and left lobes anteriorly Separates the right and left lobes anteriorly Suspends the liver from the diaphragm and anterior abdominal wall Suspends the liver from the diaphragm and anterior abdominal wall

35. Liver The ligamentum teres: The ligamentum teres: Is a remnant of the fetal umbilical vein Is a remnant of the fetal umbilical vein Runs along the free edge of the falciform ligament Runs along the free edge of the falciform ligament

36. Liver: Associated Structures The lesser omentum anchors the liver to the stomach The lesser omentum anchors the liver to the stomach The hepatic blood vessels enter the liver at the porta hepatis The hepatic blood vessels enter the liver at the porta hepatis The gallbladder rests in a recess on the inferior surface of the right lobe The gallbladder rests in a recess on the inferior surface of the right lobe

37. Liver: Associated Structures Bile leaves the liver via: Bile leaves the liver via: Bile ducts, which fuse into the common hepatic duct Bile ducts, which fuse into the common hepatic duct The common hepatic duct, which fuses with the cystic duct The common hepatic duct, which fuses with the cystic duct These two ducts form the bile duct These two ducts form the bile duct

38. Figure 23.24c Liver: Microscopic Anatomy Hexagonal-shaped liver lobules are the structural and functional units of the liver Hexagonal-shaped liver lobules are the structural and functional units of the liver Composed of hepatocyte (liver cell) plates radiating outward from a central vein Composed of hepatocyte (liver cell) plates radiating outward from a central vein Portal triads are found at each of the six corners of each liver lobule Portal triads are found at each of the six corners of each liver lobule

39. Figure 23.24d Liver: Microscopic Anatomy Portal triads consist of a bile duct and Portal triads consist of a bile duct and Hepatic artery – supplies oxygen-rich blood to the liver Hepatic artery – supplies oxygen-rich blood to the liver Hepatic portal vein – carries venous blood with nutrients from digestive viscera Hepatic portal vein – carries venous blood with nutrients from digestive viscera

40. Liver: Microscopic Anatomy Liver sinusoids – enlarged, leaky capillaries located between hepatic plates Liver sinusoids – enlarged, leaky capillaries located between hepatic plates Kupffer cells – hepatic macrophages found in liver sinusoids Kupffer cells – hepatic macrophages found in liver sinusoids

41. Liver: Microscopic Anatomy Hepatocytes’ functions include: Hepatocytes’ functions include: Production of bile Production of bile Processing bloodborne nutrients Processing bloodborne nutrients Storage of fat-soluble vitamins Storage of fat-soluble vitamins Detoxification Detoxification Secreted bile flows between hepatocytes toward the bile ducts in the portal triads Secreted bile flows between hepatocytes toward the bile ducts in the portal triads

42. Composition of Bile A yellow-green, alkaline solution containing bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes A yellow-green, alkaline solution containing bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes Bile salts are cholesterol derivatives that: Bile salts are cholesterol derivatives that: Emulsify fat Emulsify fat Facilitate fat and cholesterol absorption Facilitate fat and cholesterol absorption Help solubilize cholesterol Help solubilize cholesterol Enterohepatic circulation recycles bile salts Enterohepatic circulation recycles bile salts The chief bile pigment is bilirubin, a waste product of heme The chief bile pigment is bilirubin, a waste product of heme

43. The Gallbladder Thin-walled, green muscular sac on the ventral surface of the liver Thin-walled, green muscular sac on the ventral surface of the liver Stores and concentrates bile by absorbing its water and ions Stores and concentrates bile by absorbing its water and ions Releases bile via the cystic duct, which flows into the bile duct Releases bile via the cystic duct, which flows into the bile duct

44. Regulation of Bile Release Acidic, fatty chyme causes the duodenum to release: Acidic, fatty chyme causes the duodenum to release: Cholecystokinin (CCK) and secretin into the bloodstream Cholecystokinin (CCK) and secretin into the bloodstream Bile salts and secretin transported in blood stimulate the liver to produce bile Bile salts and secretin transported in blood stimulate the liver to produce bile Vagal stimulation causes weak contractions of the gallbladder Vagal stimulation causes weak contractions of the gallbladder

45. Regulation of Bile Release Cholecystokinin causes: Cholecystokinin causes: The gallbladder to contract The gallbladder to contract The hepatopancreatic sphincter to relax The hepatopancreatic sphincter to relax As a result, bile enters the duodenum As a result, bile enters the duodenum