1. PowerPoint ® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College C H A P T E R © 2013 Pearson Education, Inc.© Annie Leibovitz/Contact Press Images The Digestive System: Part B 23

2. © 2013 Pearson Education, Inc. Pharynx Food passes from mouth  oropharynx  laryngopharynx –Allows passage of food, fluids, and air –Stratified squamous epithelium lining; mucus- producing glands –Skeletal muscle layers: inner longitudinal, outer pharyngeal constrictors

3. © 2013 Pearson Education, Inc. Esophagus Flat muscular tube from laryngopharynx to stomach Pierces diaphragm at esophageal hiatus Joins stomach at cardial orifice Gastroesophageal (cardiac) sphincter Surrounds cardial orifice

4. © 2013 Pearson Education, Inc. Homeostatic Imbalance Heartburn –Stomach acid regurgitates into esophagus –Likely with excess food/drink, extreme obesity, pregnancy, running –Also with hiatal hernia - structural abnormality Part of stomach above diaphragm Can  esophagitis, esophageal ulcers, esophageal cancer

5. © 2013 Pearson Education, Inc. Esophagus Esophageal mucosa contains stratified squamous epithelium –Changes to simple columnar at stomach Esophageal glands in submucosa secrete mucus to aid in bolus movement Muscularis externa - skeletal superiorly; mixed in middle; smooth inferiorly Adventitia instead of serosa

6. © 2013 Pearson Education, Inc. Figure 23.12a Microscopic structure of the esophagus. Mucosa (stratified squamous epithelium) Submucosa (areolar connective tissue) Lumen Muscularis externa Circular layer Longitudinal layer Adventitia (fibrous connective tissue)

7. © 2013 Pearson Education, Inc. Figure 23.12b Microscopic structure of the esophagus. Esophagus-stomach junction Mucosa (stratified squamous epithelium) Simple columnar epithelium of stomach

8. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Bolus of food Tongue Pharynx Epiglottis Glottis Trachea During the buccal phase, the upper esophageal sphincter is contracted. The tongue presses against the hard palate, forcing the food bolus into the oropharynx. 1 Uvula Bolus Epiglottis Esophagus The pharyngeal-esophageal phase begins as the uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after food enters. Peristalsis moves food through the esophagus to the stomach. The gastroesophageal sphincter surrounding the cardial orifice opens, and food enters the stomach. Relaxed muscles Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Relaxed muscles Circular muscles contract Gastroesophageal sphincter opens Upper esophageal sphincter Bolus 2 4 3 5 Stomach Slide 7

9. © 2013 Pearson Education, Inc. Stomach: Gross Anatomy In upper left quadrant; temporary storage; digestion of bolus to chyme Cardial part (cardia) –Surrounds cardial orifice Fundus –Dome-shaped region beneath diaphragm Body –Midportion

10. © 2013 Pearson Education, Inc. Stomach: Gross Anatomy Pyloric part –Antrum (superior portion)  pyloric canal  pylorus –Pylorus continuous with duodenum through pyloric valve (sphincter controlling stomach emptying)

11. © 2013 Pearson Education, Inc. Figure 23.14a Anatomy of the stomach. Cardia Esophagus Muscularis externa Lesser curvature Duodenum Pyloric sphincter (valve) at pylorus Pyloric canal Pyloric antrum Greater curvature Rugae of mucosa Lumen Body Serosa Fundus Oblique layer Circular layer Longitudinal layer

12. © 2013 Pearson Education, Inc. Figure 23.14b Anatomy of the stomach. Liver (cut) Lesser curvature Greater curvature Spleen Body Fundus

13. © 2013 Pearson Education, Inc. Stomach: Gross Anatomy Greater curvature - convex lateral surface Lesser curvature - concave medial surface Mesenteries tether stomach –Lesser omentum From liver to lesser curvature –Greater omentum – contains fat deposits & lymph nodes Greater curvature  over small intestine  spleen & transverse colon  mesocolon

14. © 2013 Pearson Education, Inc. Figure 23.30a Mesenteries of the abdominal digestive organs. Liver Falciform ligament Gallbladder Spleen Stomach Ligamentum teres Greater omentum Small intestine Cecum

15. © 2013 Pearson Education, Inc. Figure 23.30b Mesenteries of the abdominal digestive organs. Liver Lesser omentum Small intestine Cecum Urinary bladder Gallbladder Stomach Duodenum Transverse colon

16. © 2013 Pearson Education, Inc. Greater omentum Transverse colon Transverse mesocolon Descending colon Mesentery Sigmoid mesocolon Jejunum Sigmoid colon Ileum Figure 23.30c Mesenteries of the abdominal digestive organs.

17. © 2013 Pearson Education, Inc. Stomach: Gross Anatomy ANS nerve supply –Sympathetic from thoracic splanchnic nerves via celiac plexus –Parasympathetic via vagus nerve Blood supply –Celiac trunk (gastric and splenic branches) –Veins of hepatic portal system

18. © 2013 Pearson Education, Inc. Stomach: Microscopic Anatomy Four tunics Muscularis and mucosa modified –Muscularis externa Three layers of smooth muscle Inner oblique layer allows stomach to churn, mix, move, and physically break down food

19. © 2013 Pearson Education, Inc. Surface epithelium Mucosa Lamina propria Muscularis mucosae Oblique layer Circular layer Longitudinal layer Submucosa (contains submucosal plexus) Muscularis externa (contains myenteric plexus) Serosa Layers of the stomach wall Stomach wall Figure 23.15a Microscopic anatomy of the stomach.

20. © 2013 Pearson Education, Inc. Stomach: Microscopic Anatomy Mucosa –Simple columnar epithelium composed of mucous cells Secrete two-layer coat of alkaline mucus –Surface layer traps bicarbonate-rich fluid beneath it –Dotted with gastric pits  gastric glands Gastric glands produce gastric juice

21. © 2013 Pearson Education, Inc. Enteroendocrine cell Enlarged view of gastric pits and gastric glands Chief cell Parietal cell Mucous neck cells Surface epithelium (mucous cells) Gastric pits Gastric pit Gastric gland Figure 23.15b Microscopic anatomy of the stomach.

22. © 2013 Pearson Education, Inc. Gastric Glands Cell types –Mucous neck cells (secrete thin, acidic mucus of unknown function) –Parietal cells –Chief cells –Enteroendocrine cells

23. © 2013 Pearson Education, Inc. Figure 23.15c Microscopic anatomy of the stomach. Mitochondria Parietal cell Chief cell Enteroendocrine cell Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland HCI Pepsin Pepsinogen

24. © 2013 Pearson Education, Inc. Gastric Gland Secretions Glands in fundus and body produce most gastric juice Parietal cell secretions –Hydrochloric acid (HCl)  pH 1.5–3.5 denatures protein, activates pepsin, breaks down plant cell walls, kills many bacteria –Intrinsic factor Glycoprotein required for absorption of vitamin B 12 in small intestine

25. © 2013 Pearson Education, Inc. Gastric Gland Secretions Chief cell secretions –Pepsinogen - inactive enzyme Activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism) –Lipases Digest ~15% of lipids

26. © 2013 Pearson Education, Inc. Gastric Gland Secretions Enteroendocrine cells –Secrete chemical messengers into lamina propria Act as paracrines –Serotonin and histamine Hormones –Somatostatin (also acts as paracrine) and gastrin

27. © 2013 Pearson Education, Inc. Mucosal Barrier Harsh digestive conditions in stomach Has mucosal barrier to protect –Thick layer of bicarbonate-rich mucus –Tight junctions between epithelial cells Prevent juice seeping underneath tissue –Damaged epithelial cells quickly replaced by division of stem cells Surface cells replaced every 3–6 days

28. © 2013 Pearson Education, Inc. Homeostatic Imbalance Gastritis –Inflammation caused by anything that breaches mucosal barrier Peptic or gastric ulcers –Erosions of stomach wall Can perforate  peritonitis; hemorrhage –Most caused by Helicobacter pylori bacteria –Some by NSAIDs

29. © 2013 Pearson Education, Inc. Figure 23.16 Photographs of a gastric ulcer and the H. pylori bacteria that most commonly cause it. A gastric ulcer lesion H. pylori bacteria Bacteria Mucosa layer of stomach

30. © 2013 Pearson Education, Inc. Digestive Processes in the Stomach Mechanical breakdown Denaturation of proteins by HCl Enzymatic digestion of proteins by pepsin (and milk protein by rennin in infants) Delivers chyme to small intestine

31. © 2013 Pearson Education, Inc. Digestive Processes in the Stomach Lipid-soluble alcohol and aspirin absorbed into blood Only stomach function essential to life –Secretes intrinsic factor for vitamin B 12 absorption B 12 needed  mature red blood cells Lack of intrinsic factor causes pernicious anemia Treated with B 12 injections

32. © 2013 Pearson Education, Inc. Regulation of Gastric Secretion Neural and hormonal mechanisms Gastric mucosa  up to 3 L gastric juice/day Vagus nerve stimulation  secretion  Sympathetic stimulation  secretion  Hormonal control largely gastrin –   Enzyme and HCl secretion –Most small intestine secretions - gastrin antagonists

33. © 2013 Pearson Education, Inc. Regulation of Gastric Secretion Three phases of gastric secretion –Cephalic (reflex) phase – conditioned reflex triggered by aroma, taste, sight, thought –Gastric phase – lasts 3–4 hours; ⅔ gastric juice released Stimulated by distension, peptides, low acidity, gastrin (major stimulus) Enteroendocrine G cells stimulated by caffeine, peptides, rising pH  gastrin

34. © 2013 Pearson Education, Inc. Stimuli of Gastric Phase Gastrin  enzyme and HCl release –Low pH inhibits gastrin secretion (as between meals) Buffering action of ingested proteins  rising pH  gastrin secretion Three chemicals - ACh, histamine, and gastrin - stimulate parietal cells through second- messenger systems –All three are necessary for maximum HCl secretion

35. © 2013 Pearson Education, Inc. HCl Formation Parietal cells pump H + (from carbonic acid breakdown) into stomach lumen –K + goes into cells to balance charge –HCO 3 – from carbonic acid breakdown  blood (via Cl – and HCO 3 – antiporter)  blood leaving stomach more alkaline  Alkaline tide –Cl – (from blood plasma via antiporter) follows H +  HCl

36. © 2013 Pearson Education, Inc. HCI Parietal cell Interstitial fluid HCO 3 − - Cl − antiporter Alkaline tide H + -K + ATPase Stomach lumenChief cell Gastric gland H+H+ K+K+ CO 2 H2OH2O H 2 CO 3 + HCO 3 − H+H+ K+K+ Carbonic anhydrase HCO 3 − Blood capillary Cl − Figure 23.18 Mechanism of HCl secretion by parietal cells.

37. © 2013 Pearson Education, Inc. Regulation of Gastric Secretion Intestinal phase –Stimulatory component Partially digested food enters small intestine  brief intestinal gastrin release –Inhibitory effects (enterogastric reflex and enterogastrones) Chyme with H +, fats, peptides, irritating substances  inhibition

38. © 2013 Pearson Education, Inc. Enterogastric Reflex Three reflexes act to –Inhibit vagal nuclei in medulla –Inhibit local reflexes –Activate sympathetic fibers  tightening of pyloric sphincter  no more food entry to small intestine  Decreased gastric activity  protects small intestine from excessive acidity

39. © 2013 Pearson Education, Inc. Intestinal Phase Enterogastrones released –Secretin, cholecystokinin (CCK), vasoactive intestinal peptide (VIP) All inhibit gastric secretion If small intestine pushed to accept more chyme  dumping syndrome –Nausea and vomiting –Common in gastric reduction for weight loss

40. © 2013 Pearson Education, Inc. Figure 23.17 Neural and hormonal mechanisms that regulate release of gastric juice. Lack of stimulatory impulses to parasym- pathetic center Gastrin secretion declines Overrides parasym- pathetic controls Sympathetic nervous system activation Cerebral cortex G cells Emotional stress Excessive acidity (pH < 2) in stomach Loss of appetite, depression Entero- gastric reflex Local reflexes Pyloric sphincter Vagal nuclei in medulla Distension of duodenum; presence of fatty, acidic, or hypertonic chyme; and/or irritants in the duodenum Release of enterogastrones (secretin, cholecystokinin, vasoactive intestinal peptide) Distension; presence of fatty, acidic, partially digested food in the duodenum Intestinal (enteric) gastrin release to blood Brief effect Gastrin release to blood Vagus nerve Vagus nerve Conditioned reflex Local reflexes Vagovagal reflexes G cells Presence of partially digested foods in duodenum or distension of the duodenum when stomach begins to empty Stimulate Inhibit Hypothalamus and medulla oblongata Cerebral cortex Medulla Stomach distension activates stretch receptors Food chemicals (especially peptides and caffeine) and rising pH activate chemoreceptors Stimulation of taste and smell receptors Sight and thought of food 1 1 2 1 2 1 2 1 2 1 Stimulatory events Inhibitory events Cephalic phase Gastric phase Intestinal phase Stomach secretory activity

41. © 2013 Pearson Education, Inc. Response of the Stomach to Filling Stretches to accommodate incoming food –Pressure constant until 1.5 L food ingested Reflex-mediated receptive relaxation –Coordinated by swallowing center of brain stem –Gastric accommodation Plasticity (stress-relaxation response) of smooth muscle (see Chapter 9)

42. © 2013 Pearson Education, Inc. Gastric Contractile Activity Peristaltic waves move toward pylorus at rate of 3 per minute –Basic electrical rhythm (BER) set by enteric pacemaker cells (formerly interstitial cells of Cajal) –Pacemaker cells linked by gap junctions  entire muscularis contracts Distension and gastrin increase force of contraction

43. © 2013 Pearson Education, Inc. Gastric Contractile Activity Most vigorous near pylorus Chyme is either –Delivered in ~3 ml spurts to duodenum, or –Forced backward into stomach

44. © 2013 Pearson Education, Inc. Figure 23.19 Deglutition (swallowing). Slide 1 Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus. The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum. Retropulsion: The peristaltic wave closes the pyloric valve, forcing most of the contents of the pylorus backward into the stomach. 2 Propulsion: Peristaltic waves move from the fundus toward the pylorus 13 Pyloric valve closed Pyloric valve slightly opened Pyloric valve closed

45. © 2013 Pearson Education, Inc. Figure 23.19 Deglutition (swallowing). Slide 2 Propulsion: Peristaltic waves move from the fundus toward the pylorus 1 Pyloric valve closed

46. © 2013 Pearson Education, Inc. Figure 23.19 Deglutition (swallowing). Slide 3 Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus. The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum. 2 Propulsion: Peristaltic waves move from the fundus toward the pylorus 1 Pyloric valve closed Pyloric valve slightly opened

47. © 2013 Pearson Education, Inc. Figure 23.19 Deglutition (swallowing). Slide 4 Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus. The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum. Retropulsion: The peristaltic wave closes the pyloric valve, forcing most of the contents of the pylorus backward into the stomach. 2 Propulsion: Peristaltic waves move from the fundus toward the pylorus 13 Pyloric valve closed Pyloric valve slightly opened Pyloric valve closed

48. © 2013 Pearson Education, Inc. Regulation of Gastric Emptying As chyme enters duodenum –Receptors respond to stretch and chemical signals –Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling Carbohydrate-rich chyme moves quickly through duodenum Fatty chyme remains in duodenum 6 hours or more

49. © 2013 Pearson Education, Inc. Presence of fatty, hypertonic, acidic chyme in duodenum Duodenal entero- endocrine cells Chemoreceptors and stretch receptors SecreteTarget Enterogastrones (secretin, cholecystokinin, vasoactive intestinal peptide) Via short reflexes Via long reflexes Duodenal stimuli decline Enteric neurons CNS centers sympathetic activity; parasympathetic activity Contractile force and rate of stomach emptying decline Initial stimulus Stimulate Inhibit Figure 23.20 Neural and hormonal factors that inhibit gastric emptying. Physiological response Result

50. © 2013 Pearson Education, Inc. Homeostatic Imbalance Vomiting (emesis) caused by Extreme stretching Intestinal irritants, e.g., bacterial toxins, excessive alcohol, spicy food, certain drugs Chemicals/sensory impulses  emetic center of medulla Excessive vomiting  dehydration, electrolyte and acid-base imbalances (alkalosis)

51. © 2013 Pearson Education, Inc. Small Intestine: Gross Anatomy Major organ of digestion and absorption 2-4 m long; from pyloric sphincter to ileocecal valve Subdivisions –Duodenum (retroperitoneal) –Jejunum (attached posteriorly by mesentery) –Ileum (attached posteriorly by mesentery)

52. © 2013 Pearson Education, Inc. Figure 23.1 Alimentary canal and related accessory digestive organs. Mouth (oral cavity) Tongue* Esophagus Liver* Gallbladder* Small intestine Salivary glands* Pharynx Stomach Pancreas* Large intestine (Spleen) Parotid gland Sublingual gland Submandibular gland Duodenum Jejunum Ileum Anus Transverse colon Descending colon Ascending colon Cecum Sigmoid colon Rectum Appendix Anal canal

53. © 2013 Pearson Education, Inc. Duodenum Curves around head of pancreas; shortest part – 25 cm Bile duct (from liver) and main pancreatic duct (from pancreas) –Join at hepatopancreatic ampulla –Enter duodenum at major duodenal papilla –Entry controlled by hepatopancreatic sphincter

54. © 2013 Pearson Education, Inc. Figure 23.21 The duodenum of the small intestine, and related organs. Right and left hepatic ducts of liver Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter Head of pancreas Hepatopancreatic ampulla and sphincter Duodenum Mucosa with folds Gallbladder Major duodenal papilla Cystic duct

55. © 2013 Pearson Education, Inc. Jejunum and Ileum Jejunum –Extends from duodenum to ileum –About 2.5 m long Ileum –Joins large intestine at ileocecal valve –About 3.6 m long

56. © 2013 Pearson Education, Inc. Gross Anatomy of Small Intestine Vagus nerve (parasympathetic) and sympathetics from thoracic splanchnic nerves serve small intestine Superior mesenteric artery brings blood supply Veins (carrying nutrient-rich blood) drain into superior mesenteric veins  hepatic portal vein  liver

57. © 2013 Pearson Education, Inc. Structural Modifications Increase surface area of proximal part for nutrient absorption –Circular folds (plicae circulares) –Villi –Microvilli

58. © 2013 Pearson Education, Inc. Structural Modifications Circular folds –Permanent folds (~1 cm deep) that force chyme to slowly spiral through lumen  more  nutrient absorption Villi –Extensions (~1 mm high) of mucosa with capillary bed and lacteal for absorption Microvilli (brush border) – contain enzymes for carbohydrate and protein digestion

59. © 2013 Pearson Education, Inc. Figure 23.22a Structural modifications of the small intestine that increase its surface area for digestion and absorption. Vein carrying blood to hepatic portal vessel Muscle layers Circular folds Villi Lumen

60. © 2013 Pearson Education, Inc. Microvilli (brush border) Absorptive cells Villus Lacteal Goblet cell Blood capillaries Mucosa- associated lymphoid tissue Intestinal crypt Muscularis mucosae Duodenal gland Enteroendocrine cells Venule Lymphatic vessel Submucosa Figure 23.22b Structural modifications of the small intestine that increase its surface area for digestion and absorption.

61. © 2013 Pearson Education, Inc. Figure 23.22c Structural modifications of the small intestine that increase its surface area for digestion and absorption. Goblet cells Absorptive cells Villi Intestinal crypt

62. © 2013 Pearson Education, Inc. Figure 23.23 Microvilli of the small intestine. Mucus granules Microvilli forming the brush border Absorptive cell

63. © 2013 Pearson Education, Inc. Intestinal Crypts Intestinal crypt epithelium renewed every 2-4 days –Most - secretory cells that produce intestinal juice –Enteroendocrine cells  enterogastrones –Intraepithelial lymphocytes (IELs) Release cytokines that kill infected cells –Paneth cells Secrete antimicrobial agents (defensins and lysozyme) –Stem cells divide to produce crypt cells

64. © 2013 Pearson Education, Inc. Homeostatic Imbalance Chemotherapy targets rapidly dividing cells –Kills cancer cells –Kills rapidly dividing GI tract epithelium  nausea, vomiting, diarrhea

65. © 2013 Pearson Education, Inc. Mucosa Peyer's patches protect especially distal part against bacteria –May protrude into submucosa B lymphocytes leave intestine, enter blood, protect intestinal lamina propria with their IgA Duodenal (Brunner's) glands of the duodenum secrete alkaline mucus to neutralize acidic chyme

66. © 2013 Pearson Education, Inc. Intestinal Juice 1-2 L secreted daily in response to distension or irritation of mucosa Slightly alkaline; isotonic with blood plasma Largely water; enzyme-poor (enzymes of small intestine only in brush border); contains mucus Facilitates transport and absorption of nutrients

67. © 2013 Pearson Education, Inc. The Liver and Gallbladder Accessory organs Liver –Many functions; only digestive function  bile production Bile – fat emulsifier Gallbladder –Chief function  bile storage

68. © 2013 Pearson Education, Inc. Liver Largest gland in body Four lobes—right, left, caudate, and quadrate

69. © 2013 Pearson Education, Inc. Liver Falciform ligament –Separates larger right and smaller left lobes –Suspends liver from diaphragm and anterior abdominal wall Round ligament (ligamentum teres) –Remnant of fetal umbilical vein along free edge of falciform ligament

70. © 2013 Pearson Education, Inc. Figure 23.24a Gross anatomy of the human liver. Sternum Nipple Liver Right lobe of liver Gallbladder Bare area Falciform ligament Left lobe of liver Round ligament (ligamentum teres)

71. © 2013 Pearson Education, Inc. Lesser omentum (in fissure) Left lobe of liver Porta hepatis containing hepatic artery (left) and hepatic portal vein (right) Quadrate lobe of liver Ligamentum teres Bare area Caudate lobe of liver Sulcus for inferior vena cava Hepatic vein (cut) Bile duct (cut) Right lobe of liver Gallbladder Figure 23.24b Gross anatomy of the human liver.

72. © 2013 Pearson Education, Inc. Liver: Associated Structures Lesser omentum anchors liver to stomach Hepatic artery and vein enter at porta hepatis Bile ducts –Common hepatic duct leaves liver –Cystic duct connects to gallbladder –Bile duct formed by union of common hepatic and cystic ducts

73. © 2013 Pearson Education, Inc. Right and left hepatic ducts of liver Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter Head of pancreas Hepatopancreatic ampulla and sphincter Duodenum Mucosa with folds Gallbladder Major duodenal papilla Cystic duct Figure 23.21 The duodenum of the small intestine, and related organs.

74. © 2013 Pearson Education, Inc. Liver: Microscopic Anatomy Liver lobules –Hexagonal structural and functional units –Composed of plates of hepatocytes (liver cells) Filter and process nutrient-rich blood –Central vein in longitudinal axis

75. © 2013 Pearson Education, Inc. Figure 23.25a–b Microscopic anatomy of the liver. Lobule Central vein Connective tissue septum

76. © 2013 Pearson Education, Inc. Liver: Microscopic Anatomy Portal triad at each corner of lobule –Branch of hepatic artery supplies oxygen –Branch of hepatic portal vein brings nutrient-rich blood –Bile duct receives bile from bile canaliculi Liver sinusoids - leaky capillaries between hepatic plates Stellate macrophages (hepatic macrophages or Kupffer cells) in liver sinusoids remove debris & old RBCs

77. © 2013 Pearson Education, Inc. Interlobular veins (to hepatic vein) Central vein Sinusoids Plates of hepatocytes Portal vein Stellate macrophages in sinusoid walls Bile canaliculi Bile duct (receives bile from bile canaliculi) Fenestrated lining (endothelial cells) of sinusoids Bile duct Portal venule Portal arteriole Portal triad Figure 23.25c Microscopic anatomy of the liver.

78. © 2013 Pearson Education, Inc. Liver: Microscopic Anatomy Hepatocytes – increased rough & smooth ER, Golgi, peroxisomes, mitochondria Hepatocyte functions –Process bloodborne nutrients –Store fat-soluble vitamins –Perform detoxification –Produce ~900 ml bile per day

79. © 2013 Pearson Education, Inc. Liver Regenerative capacity –Restores full size in 6-12 months after 80% removal –Injury  hepatocytes  growth factors  endothelial cell proliferation

80. © 2013 Pearson Education, Inc. Homeostatic Imbalance Hepatitis –Usually viral infection, drug toxicity, wild mushroom poisoning Cirrhosis –Progressive, chronic inflammation from chronic hepatitis or alcoholism –Liver  fatty, fibrous  portal hypertension Liver transplants successful, but livers scarce

81. © 2013 Pearson Education, Inc. Bile Yellow-green, alkaline solution containing –Bile salts - cholesterol derivatives that function in fat emulsification and absorption –Bilirubin - pigment formed from heme Bacteria break down in intestine to stercobilin  brown color of feces –Cholesterol, triglycerides, phospholipids, and electrolytes

82. © 2013 Pearson Education, Inc. Bile Enterohepatic circulation –Recycles bile salts –Bile salts  duodenum  reabsorbed from ileum  hepatic portal blood  liver  secreted into bile

83. © 2013 Pearson Education, Inc. The Gallbladder Thin-walled muscular sac on ventral surface of liver Stores and concentrates bile by absorbing water and ions Muscular contractions release bile via cystic duct, which flows into bile duct

84. © 2013 Pearson Education, Inc. The Gallbladder High cholesterol; too few bile salts  gallstones (biliary calculi) –Obstruct flow of bile from gallbladder May cause obstructive jaundice –Gallbladder contracts against sharp crystals  pain –Treated with drugs, ultrasound vibrations (lithotripsy), laser vaporization, surgery