The document summarizes the structure and functions of the liver, gallbladder, and pancreas. It describes that the liver is the largest internal organ located in the upper right abdomen. It performs many metabolic functions like producing bile, storing glucose and vitamins, and breaking down drugs and toxins. The gallbladder stores and concentrates bile produced by the liver. The pancreas is located behind the stomach and contains both exocrine cells that secrete digestive enzymes and endocrine cells that secrete hormones like insulin and glucagon to regulate blood sugar levels.

1. Digestive System III
Liver
Gallbladder
Pancreas

2. Liver
 occupies the upper right region
of the abdominal cavity

3. Liver is the largest internal organ
 is subdivided into
two large lobes (right and left)
two small lobes (quadrate and caudate)
 is enclosed in a capsule (capsule of Glisson)
 is partially covered by the visceral peritoneum
 is associated with the gallbladder

4. Liver composition
 Parenchyma
- consists of epithelial cells - hepatocytes
- arises from the endoderm
 Stroma
- consists of connective tissue trabeculae
- contains blood and lymphatic vessels,
nerves, and bile ducts
- divides parenchyma into lobules

5. Connective tissue is poor-developed in the human liver
 the human liver
connective tissue
in the pig liver Þ

6. Liver functions
Bile production – exocrine function
ß
Ý
so-called “endocrine” functions

7. Liver is involved in many metabolic pathways
 produces blood plasma proteins
(albumins, prothrombin, fibrinogen,
nonimmune a- and b-globulins, etc.)
 stores the blood glucose as glycogen and
releases glucose back after glycogenolysis
 stores lipid-soluble vitamins – A, D, K
 synthesizes and stores cholesterol
 stores iron ions as ferritin or hemosiderin
 synthesizes urea from ammonium ions

8. Liver degrades drugs, toxins, alcohol, and hormones
 Detoxication and degradation
- occur in hepatocyte sER Þ
- include
oxidation
conjugation
conversation

9. Liver blood supply
 Liver receives blood from two blood vessels
the hepatic artery
the portal vein
the liver hilum or porta hepatis Þ

10. Portal vein carries the venous blood
 from the digestive tract, spleen,
and pancreas Þ
 portal blood contains
– nutrients and toxic materials
– erythrocyte breakdown products
– hormones

11. Blood vessels pass in connective tissue with bile ducts
 Triad (portal area) includes interlobular
– artery
– vein (from v. porta)
– bile duct
ß

12. Interlobular vessels give rise to capillaries
 capillaries (hepatic sinusoids)
– pass trough lobule
– empty into the central vein

13. Hepatic sinusoids carry mixed blood
hepatic sinusoids
ß

14. Central vein is a terminal venule
 receives blood from sinusoids
Û

15. Central vein begins the vinous blood outflow
a central vein
ß
the sublobular veins
ß
the hepatic vein
ß
the inferior vena cava

16. Hepatic lobules
 are the liver morphofunctional units

17. Hepatic lobule composition
 hepatocytes arranged in plates
 hepatic sinusoids
 perisinusoidal spaces (spaces of Disse)
 bile capillaries (canaliculi)
 central veins

18. Classic hepatic lobule
 is a hexagonal mass of tissue
 a central vein is at the center
 the triads are at the angles
 hepatic plates radiate from the center to periphery
 sinusoids travel between plates
 blood flows from the periphery towards the center
 bile flows from the center towards the periphery

19. Portal lobule emphasizes the liver exocrine function
 is a triangular mass of tissue
 the central veins are at the angles
 the triad is at the center
 blood flows from the center to the periphery
 bile flows from the periphery to the center

20. Liver acinus
 is a diamond-shaped mass of tissue
 the short axis is between the triads
 the long axis is between the central veins

21. Plates of hepatocytes
 consist of two anastomosing cell rows
 bile canaliculus is between the rows
 are surrounded by the blood sinusoids
 delicate network of the reticular fibers
supports plates
Ü

22. Hepatocytes
 are large polygonal cells
 contain 1 or 2 nuclei with several nucleoli
 may be tetraploid

23. Hepatocytes are rich in organelles
 rER and sER
 mitochondria
 Golgi apparatus
 peroxisomes
Û
ÞÝ

24. Hepatocyte inclusions
glycogen clumps
ß
Û
lipid droplets

25. Hepatocyte polarization
 Vascular pole
- faces blood sinusoids
- is involved in the “endocrine” function
(blood-hepatocyte exchange)
 Biliar pole
- faces bile canaliculi
- is involved in the exocrine function
(bile secretion)

26. Hepatocytes are capable for regeneration
 Physiologic regeneration
hepatocyte lifespan is about 5 months
hepatocytes can be renewed
undifferentiated cells are
in the periportal areas Þ
 Reparative regeneration
occurs when liver substance is lost after trauma or surgery

27. Bile canaliculi
 are intercellular gaps within the hepatic plates
Û

28. Bile canaliculi lack their own wall
 are isolated by the hepatocyte tight junctions

29. Bile canaliculi empty into the bile duct
 bile duct is a part of the triad
ß
Û

30. Bile duct is lined with cuboidal epithelial cells
Û

31. Hepatic blood capillaries – hepatic sinusoids
 are sinusoidal fenestrated and discontinuous
Ý
are lined with fenestrated endothelial cells

32. Hepatic sinusoids contain Kupffer cells
 Kupffer cells are hepatic macrophages
Û

33. Kupffer cells
 belong to the mononuclear
phagocytotic system
 arise from blood monocytes
pit-cell is a large granulated
lymphocyte
Ý

34. Kupffer cell functions
 degradation of damaged or senile erythrocytes
 conversation ferritin to hemosiderin
 phagocytosis of bacteria and antigens
 initiation of immune reactions

35. Perisinusoidal space (space of Disse)
 is between vascular hepatocyte pole and sinusoid
 contains a few reticular fibers and amorphous substance
Ý
hepatocytes project microvilli into space of Disse

36. Space of Disse is a site of
 exchange between blood and hepatocytes
 hepatic lymph origination
 hemopoiesis in the fetal period and
in cases of chronic anemia in the adult

37. Space of Disse contains lipocytes (stellate or Ito cells)
 are located between hepatocytes
 lack contact with bile canaliculi
 contain numerous lipid droplets

38. Lipocyte functions
 storage of vitamin A
 synthesis of reticular fibers and amorphous substance
 In pathology
- lose their lipids and differentiate into myofibroblast-like cells
- synthesize collagen fibers resulting in liver fibrosis
- may contract resulting in portal hypertension

39. Gallbladder
 is attached to the visceral surface of the liver

40. Gallbladder functions
 bile storage
 bile concentration
 bile release to the duodenum as required

41. Bile takes part in digestion
 emulsifies lipids
 activates pancreatic lipases
 facilitates fatty acid absorption
Bile composition:
water
electrolytes
phospholipids
cholesterol
bile acids
bile pigments (bilirubin)
Û

42. Gallbladder wall structure
 Mucosa
 Mascularis externa
 Adventitia/Serosa

43. Gallbladder mucosa
 epithelium
 lamina propria

44. Gallbladder epithelium
 simple columnar striated
Û
brush border

45. Hormone cholecystokinin regulates the bile injection
 is produced by enteroendocrine cells of the duodenum
 is released in response to a fatty chyme
 induce the gallbladder muscle contractions

46. Pancreas
 is located behind the stomach
 is enclosed in a capsule and
partially covered with serosa
 is subdivided into
head
body
tail

47. Pancreas composition
 Parenchyma
- consists of epithelial cells
- arises from the endoderm
 Stroma
- consists of connective tissue trabeculae
- contains blood and lymphatic vessels,
nerves, and ducts
- divides parenchyma into lobules

48. Pancreas is mixed gland
 Exocrine component
produces pancreatic juice
 Endocrine component
secretes hormones

49. Exocrine pancreas
 is compound
branched
tubulo-alveolar
serous (protein-producing) gland
 main and accessory pancreatic ducts empty into the duodenum Ý

50. Pancreatic secretory unit - acinus
 is round with narrow lumen

51. Acinar cells
 are pyramidal
 nuclei are round and centrally located
 broad basal portion is basophilic due to rER
 apical portion is acidophilic due to secretory (zymogen) granules

52. Acinar cell ultrastructure
 zymogen granules in the apical pole Þ
 rER in the basal pole Þ

53. Acinar cells secrete a variety of digestive enzymes
 Trypsin, chymotrypsin, peptidases
– digest proteins up to amino acids
 Amylase
– digests carbohydrates up to glucose
 Lipases
– digest lipids up to glycerol and fatty acids
 Nucleases
– digest nucleic acids up to nucleotides

54. Zymogen granules contain inactive enzymes
 proenzymes are activated when reach
the intestinal lumen ß

55. Exocrine pancreas duct system
 Intercalated ducts
 Intralobular ducts
 Interlobular ducts
 Main and accessory pancreatic ducts Þ

56. Intercalated duct
 is narrow tubule lined with squamous or cuboidal cells
 may begin within the acinus (compound acinus)
 its cells in the acinus are called centroacinar cells

57. Centroacinar cells exist in the compound acinus
 but belong to the intercalated duct Þ
ß

58. Intercalated duct takes part in secretion
 Adds
water
sodium
bicarbonate to the pancreatic juice
 Intercalated duct secretion
- neuyralizes acidic gastric chyme
- establishes the optimal pH for pancreatic enzyme activity

59. Intralobular and interlobular ducts
 are lined with simple cuboidal epithelium

60. Pancreas exocrine secretion hormonal regulation
 Hormones of enteroendocrine cells from the duodenum
pancreozymin Þ stimulates acinar cells
secretin Þ stimulates intercalated duct cells
 Pancreatic hormones
insulin and VIP Þ stimulate exocrine secretion
glucagon and PP Þ inhibit exocrine secretion

61. Pancreas exocrine secretion nervous regulation
 parasympathetic fibers stimulate both acinar and duct cells

62. Endocrine pancreas
 consists of pancreatic (Langerhans) islets
 islets are scattered throughout the gland
Þ

63. Islet composition
 endocrine cells
 fenestrated sinusoidal capillaries
Û

64. Islet endocrine cell types
 B cells
 A cells
 D cells
 D1cells
 PP cells

65. B cells constitute about 70% of the islet population
 occupy the islet central portion
 secrete insulin

66. Insulin decreases blood glucose levels
 Effects hepatocytes and skeletal muscles
– stimulates uptake of glucose from circulation
– activates glycogen synthesis
 Effects the white adipose cells
– stimulates uptake of glucose from circulation
– stimulates glycerol synthesis
– inhibits lipase activity

67. A cells constitute 15-20% of the islet population
 occupy the islet periphery
 secrete glucagon

68. Glucagon increases blood glucose levels
Stimulates
 glucose release into the bloodstream
 glycogenolysis (breakdown of glycogen)
 gluconeogenesis (synthesis of glucose from amino acids)
 lipase and lipid mobilization in adipose cells

69. Insulin and glucagon are antagonists

70. D cells constitute about 5-10% of the islet population
 occupy the islet periphery
 secrete stomatostatin
inhibits both insulin and glucagon secretion
inhibits acinar cell

71. Minor cell types in pancreatic islets
 D1 cells Þ vasoactive intestinal peptide (VIP)
– stimulates endocrine and exocrine pancreatic secretion
– decreases blood pressure
 PP cells Þ pancreatic polypeptide
– stimulates gastric chief cells
– inhibits
bile secretion
pancreatic juice production
intestinal motility

72. Regulation of the islet activity
 Blood glucose levels
increase Þ stimulate insulin production
decrease Þ stimulate glucagon production
 Nervous regulation
parasympathetic fibers Þ stimulate both insulin and glucagon secretion
sympathetic fibers Þ stimulate glucagon release but inhibit insulin secretion

73. The End
Thank you for attention!