1. LIVER AND GALLBLADDER

2. Liver Figure 24.16a 2nd largest organ Heaviest gland
Right and left lobes
Falciform ligament

3. Liver
Quadrate and caudate lobes in the right lobe
Lobules

4. Histology of the Liver Lobules Contain: Hepatocytes Bile canaliculi
Sinusoids
Stellate reticuloendothelial cells
Central vein

5. Histology of the Liver Lobules Contain:
Hepatocytes / hepatic cells (80%)
Major functional cells of the liver
Bile canaliculi
Small ducts between hepatocytes
Collect bile produced by the hepatocytes
Bile pathway*
Sinusoids
Permeable blood capillaries between rows of hepatocytes

6. Figure 24.18 From GI organs and spleen
Vitamins, nutrients, drugs, toxins, microbes
Liver Lobules
Double supply of blood
All leaves through hepatic vein

7. Histology of the Liver Lobules Contain:
Figure 24.17
Histology of the Liver
Lobules Contain:
4. Stellate reticuloendothelial cells
Fixed phagocytes in hepatocytes
Hepatic macrophages
5. Central vein

8. Figure 24.17 Histology of a lobule, the functional unit of the liver

9. Hepatic Acinus

10. Three models – pg. 924-925 Hepatic Lobule – functional unit
Portal Lobule – exocrine (bile) function
Hepatic Acinus – more recently preferred functional unit

11. Figure 24.16
Gallbladder
Sac beneath liver
Fundus, body, neck

12. Gallbladder Mucosa Simple columnar Rugae No submucosa Muscularis
Smooth muscle
Ejects bile into cystic duct
Serosa
Visceral peritoneum
FUNCTION - Store and concentrate bile

13. Bile Yellow, brown, olive
Water, bile salts, cholesterol, lecithin, ions, bile pigments
Excretory product (worn out RBCs)  bilirubin
Digestive secretion  Emulsification of triglycerides.

14. Bile Pigment Bilirubin

15. Bile pathway:
produced by hepatocytes 
bile canaliculi 
bile ductules 
bile ducts 
R and L hepatic ducts 
common hepatic duct 
cystic duct (storage) 
common bile duct 
hepatopancreatic ampulla 
duodenum to aid digestion

16. Other Liver Functions Metabolism of carbohydrates, lipids, proteins
Removal of substances
Drugs
Hormones
Excretion of bilirubin
Synthesis of bile salts
Vitamin and mineral storage
Phagocytosis
Activation of vitamin D

17. SMALL INTESTINE

18. Small Intestine Majority of digestion and absorption
Figure 24.19
Small Intestine
Majority of digestion and absorption
Pyloric sphincter  ileocecal sphincter
3 regions: Duodenum, jejunum, ileum
Same 4 layers as most of GI

19. Mucosa
Figure 24.19b

20. Figure 24.20 Histology of the small intestine

21. Mucosa
Figure 24.20
S cells
CCK cells
K cells

22. Mucosa
Figure 24.21

23. Figure 24.21

24. Figure 24.21 Brush border of Absorptive cells
Brush border enzymes work inside epithelial cells (surface of microvilli)
Carbs, proteins, nucleic acids
Some absorptive cells slough off to act in the lumen

25. Intestinal Juice Clear to yellow fluid Composition is highly variable
Hormones, enzymes, mucus, neutralizing substances
Alkaline pH
Vehicle for absorption
Composition of enzymes Depends on food actually eaten

26. Submucosa Duodenum Duodenal glands (Brunner’s) Alkaline mucous Ileum
Figure 24.21
Duodenum
Duodenal glands (Brunner’s)
Alkaline mucous
Ileum
Lymphatic nodules (Peyer’s patches)

27. Mechanical Digestion
Segmentation and Peristalsis (MMC)

28. Assigned Reading Digestion and Absorption in the small intestine
Look at pages in textbook
Pay attention to enzymes and where they act and what they break down.
Take note of when they are activated / inactivated.
Focus on tables 24.4 and 24.5 (pages )
Focus on understanding diagram on page 934

29. Absorption End products of digestion moves into the blood or lymph.
Occurs by diffusion, facilitated diffusion, osmosis and various forms of active transport.
MICELLES
CHYLOMICRON

32. Water Absorption via osmosis Fig 24
Water Absorption via osmosis Fig Based on electrolyte and nutrient [ ]

33. LARGE INTESTINE

34. Large Intestine (colon)
Completion of:
absorption
production of vitamins
formation and expulsion of feces
Terminal portion of GI tract
Ileocecal sphincter  anus
Cecum, colon, rectum, anal canal
Colon = ascending, transverse, descending, sigmoid

35. Figure 24.24

36. Histology of the L.I Summary
Mucosa
Simple columnar epithelium
No villi or permanent circular folds
Absorptive and goblet cells in crypts
Crypts of Lieberkuhn
Microvilli
Submucosa
Areolar connective tissue

37. Figure 24.25

38. Figure 24.25b

39. Figure c / d

40. Histology of the L.I Summary
Muscularis
Internal circular smooth muscle
External longitudinal muscle
Teniae coli
Haustra
Serosa
Visceral peritoneum
Omental appendices

41. Epiploic appendages or omental appendices

43. Rectum and Anus Figure 24.24b Rectum Anal canal
Anal columns  mucous membrane  longitudinal folds
Anus
Internal anal sphincter  smooth muscle
External anal sphincter  skeletal muscle

44. Mechanical Digestion
Chemical Digestion
Gastroileal reflex
Haustral churning
Peristalsis
Mass peristalsis
Bacterial fermentation
Absorption
Feces Formation
Water
Electrolytes
Some vitamins
Inorganic salts
Sloughed-off epithelial cells
Bacteria
Indigestible and unabsorbed food

45. Water Absorption via osmosis Fig 24
Water Absorption via osmosis Fig Based on electrolyte and nutrient [ ]

46. Defecation Reflex

47. Look at tables 24.6 and 24.7

48. PHASES OF DIGESTION

49. Three Phases of Digestion
Cephalic Phase
Gastric Phase
Intestinal Phase

50. Cephalic Phase Cerebral cortex, hypothalamus, and brainstem
Activated by sight, smell, thought, and taste of food.
Brainstem activates parasympathetic nuclei:
CN VII – salivation
CN IX – salivation
CN X – gastric juice
Prepares mouth and stomach for food that is about to be eaten

51. Gastric Phase Begins when food reaches the stomach
Promotes gastric secretion and motility
Neural and Hormonal regulation

52. Gastric Phase – Neural Regulation
Food entering stomach increases gastric juice pH and distends stomach walls.
Chemoreceptors and stretch receptors in stomach
Detect pH increase
Detect distention
Send nerve impulses to submucosal plexus
Submucosal plexus stimulates:
Parietal cells to secrete HCl
Muscularis to contract more vigorously
Causes mixing and initiates gastric emptying.

53. Figure 24.26 Neural Feedback Loop
Food entering stomach
Disrupts homeostasis
by increasing
CONTROLLED CONDITION
pH of gastric juice
Distention (stretching) of stomach walls
RECEPTORS
Chemoreceptors and stretch receptors in stomach detect pH increase and distension
Input
Nerve impulses
CONTROL CENTER
Return to homeostasis when response brings pH of gastric juice and distention of stomach walls back to normal (pre-eating status)
Submucosal plexus
Output
Nerve impulses (parasympathetic)
EFFECTORS
Smooth muscle in stomach wall
Parietal cells
HCI
Parietal cells secrete HCI
Smooth muscle contracts more vigorously
RESPONSE
Increase in acidity of stomach chyme; mixing of stomach contents; emptying of stomach

54. Gastric Phase – Hormonal Regulation
Food entering stomach increases gastric juice pH and distends stomach walls.
ANS is triggered to release acetylcholine.
ACh stimulates G cells in pyloric antrum and secrete gastrin hormone into blood.

55. Gastrin’s Actions Major Effects Promotes gastric juice secretion
Increases gastric motility
Promotes gastric mucosal growth
Minor Effects
Constricts lower esophageal sphincter
Relaxes pyloric and ileocecal sphincters

56. Intestinal Phase Begins when food enters the small intestine.
Inhibits gastric secretion and motility.
Promotes intestinal and pancreatic juice secretion, bile ejection, and intestinal motility.
Regulated by neural and hormonal activities.

57. Intestinal Phase – Neural Regulation
Gastric emptying of chyme into small intestine distends duodenal walls.
Stretch receptors detect distention  nerve impulses to brainstem.
Brainstem ↓ parasympathetic and ↑ sympathetic nerves to stomach and pyloric sphincter.
Gastric motility and emptying is inhibited.

58. Intestinal Phase – Hormonal Regulation
Chyme containing digested proteins and fatty acids stimulates intestinal glands to secrete cholecystokinin into blood.
Acidic chyme stimulates intestinal glands to secrete secretin into blood.

59. Secretin’s Actions
Major Effects
Stimulates secretion of pancreatic juice and bile rich in HCO3-
Minor Effects
Inhibits gastric juice secretion
Promotes normal pancreatic growth and maintenance
Enhances CCK’s effects

60. CCK’s Actions Major Effects Minor Effects
Stimulate secretion of enzyme-rich pancreatic juice
Ejection of bile from gallbladder
Opens sphincter of hepatopancreatic ampulla (oddi)
Minor Effects
Inhibits gastric emptying
Promotes normal pancreatic growth and maintenance
Enhances secretin’s effects

61. Table 24.8 Major Hormones that Control Digestion
There are at least 10 other hormones involved in the GI tract

62. Development and Aging of the Digestive System
Read the last page in your notes
Read pages in your textbook
Add any important information to your notes on these two topics.