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Gastrointestinal Tract Anatomy > Histology of the Liver, Gallbladder and Pancreas > Flashcards

Histology of the Liver, Gallbladder and Pancreas Flashcards

1
Q

What is the liver divided into?

A
  1. left lobe 2. right lobe - caudate + quadrate
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2
Q

Describr the embryological origin of the liver?

A
  1. Develops as an endodermal evagination from the wall of foregut to form hepatic diverticulum
  2. Hepatocytes divide and arrange to form cellular (liver) cords
  3. Original stalk becomes the common bile duct
  4. Outgrowth from the common bile duct forms the cystic diverticulum that form the gall bladder
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3
Q

What are the functions of the liver?

A
  1. Production of body’s circulating plasma proteins (Albumins, lipoproteins)
  2. Stores and converts several vitamins and iron
  3. Degrades drugs and toxins
  4. Involved in metabolic pathways (storage of glycogen)
  5. Bile production (exocrine function)
  6. Modify the structure and function of many hormones (endocrine functions)
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4
Q

Describe the blood supply to the liver?

A
  1. Portal vein (venous supply) (70%) - oxygen depleted 2. Hepatic artery (arterial supply) (30%) branch of celiac trunk - oxygenated blood : The liver receives blood by the Portal vein that initially supplied the intestine, pancreas and spleen
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5
Q

Where does the blood supply enter the liver?

A

porta hepatis

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6
Q

The portal blood contains?

A
  1. Nutrients and toxic materials - intestines
  2. Blood cells +breakdown products of blood cells - spleen
  3. Endocrine secretions (pancreas + enteroendocrine cells) - GIT
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7
Q

Describe the blood supply within the liver?

A
  1. Branches of portal vein and hepatic artery join to supply the sinusoidal capillaries (sinusoids) – bathe hepatocytes
  2. Draining branches of the bile duct system lead to common hepatic duct
  3. The portal vein, terminal branch of hepatic artery + bile duct course together in a Portal triad
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8
Q

What are the structural components of the liver?

A
  1. Connective tissue stroma –continuous with fibrous capsule of Glisson’s
  2. Parenchyma –organized plates of hepatocyte
  3. Sinusoidal capillaries (Sinusoids) -vascular channels between plates of hepatocytes
  4. Perisinusoidal spaces (Spaces of Disse) – between sinusoidal endothelium and hepatocytes
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9
Q

What is the Glissons capsule of the liver?

A

connective tissue capsule that branches and extends throughout the substance of the liver as septae.

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10
Q

What are the functions of Glissons capsule?

A
  1. support
  2. Channels for afferent blood vessels, lymphatic vessels and bile ducts
  3. divide the parenchyma into lobules
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11
Q

What is the hepatic lobule?

A

the structural and functional unit of the liver

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12
Q

What are the 3 ways of describing a liver lobule?

A
  1. the classic lobule 2. the portal lobule 3. the liver acinus
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13
Q

Describe the classic liver lobules?

A
  1. Anastomosing hexagonal arrangement of plates of hepatocytes radiating outward from a central vein (terminal hepatic venule) in the center (one cell thick)
  2. Plates are separated by sinusoids (with mixed portal and arterial blood) which drain into central vein
  3. the lobules are distributed by portal areas (portal canals) containing portal triads,
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14
Q

Each portal triad has?

A
  1. a terminal branch of a bile duct 2. the hepatic artery 3. portal vein
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15
Q

What is a Space of Mall?

A

At edges of portal canal (between the CT stroma and hepatocytes) - origin of lymph

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16
Q

Describe the portal lobule of the liver?

A
  1. the unit supplied and drained by a portal triad 2. Emphasizes of exocrine function of the liver functions of the liver (i.e. secretion of bile) 3. The morphological axis is the interlobular bile duct of the portal triad of the “classic “ lobule 4. The outer margins are imaginary lines drawn between three central veins closed to the portal triad 5. These lines include portions of three classic lobules that secret bile and drains into the axial bile duct
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17
Q

Describe the liver acinus?

A
  1. Lozenge shaped - smallest unit of hepatic parenchyma 2. Hepatocytes arranged in three concentric zones surrounding short axis
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18
Q

Function of the liver acinus?

A

provides best correlation between - 1. blood perfusion 2. metabolic activity 3. liver pathology

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19
Q

Describe the axes of the liver acinus?

A
  1. short axis - defined by terminal branches of the portal triad that lie along the border between two classic liver lobules 2. line drawn between two central veins closest to the short axis
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20
Q

Describe Zone 1?

A
  1. Closest to the short axis 2. Blood supply form branches of portal vein and hepatic artery 3. Corresponds to the peripheral of the classic lobule
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21
Q

Describe Zone 2?

A

between zone 1 and zone 3

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22
Q

Describe Zone 3?

A
  1. Furthest to the short axis 2. Closest to the central vein 3. Corresponds to the most central part of the classic lobule
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23
Q

What is the clinical importance of zonation of liver acinus?

A

important in description and interpretation of pattern of: 1. degeneration 2. regeneration 3. specific toxic effects

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24
Q

What is the clinical importance of zone 1?

A
  1. First to receive oxygen, nutrients and toxins from sinusoidal blood 2. First to be affected due to bile duct occlusion (bile stasis) 3. Last to die due inpaired blood circulation 4. first to regenrate
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25
Q

What is the clinical importance of zone 3?

A
  1. First to show Ischemic necrosis (centrilobular necrosis) 2. First to show fat accumulation 3. Last to respond to toxic substances and bile stasis
26
Q

Describe hepatic sinusoids?

A

lined with thin discontinuous endothelium due to: 1. large fenestrations without diaphragm 2. large gaps

27
Q

What are the cells of the hepatic sinusoids?

A
  1. stellate sinusoidal macrophages 2. Kupffer cells ( mononuclear phagocytotic system) in vessel lining
28
Q

What is the perisinusoidal space (space of Disse)?

A

lies btwn basal surfaces of hepatocytes and basal surfaces of endothelial and Kupffer cells that line the sinusoids

29
Q

Describ ethe perisinusoidal space?

A
  1. Site for exchange of materials between blood and the liver 2. Microvilli project inside
30
Q

What are the cells of the liver?

A
  1. hepatocytes 2. Ito cells (stellate cells ) 3. Kupffer cells (Wandering macrophages) 4. Endothelial cells
31
Q

Describe the hepatic stellate cells?

A
  1. Found in perisinusoidal space 2. Store vitamin A in form of retinly esters 3. In pathological conditions, they differentiate into myofibroblasts and synthesize collagen
32
Q

What are hepatocytes?

A
  1. chief functional cells of the liver. (80% of the mass of the liver)
33
Q

Describe hepatocytes?

A
  1. Hepatocytes stores glycogen - arranged in clusters of electron-dense particles
  2. arranged in plates that anastomose with one another
  3. The cells are polygonal in shape
  4. Their sides can be in contact either with sinusoids (sinusoidal face) or neighboring hepatocytes (lateral faces) lateral faces of hepatocytes is modified to form bile canaliculi
34
Q

Describe the histology of the hepatocytes?

A
  1. Hepatocyte nuclei are round, with one or two prominent nucleoli 2. Some cells have a single nucleus, but binucleate cells are common 3.
35
Q

Describe the lymph pathway?

A
  1. Hepatic lymph originates in the perisinusoidal space 2. Drains in the space of Mall - lymphatic capillaries 3. Enters the thoracic duct 4. microvilli are present abundantly on the sinusoidal face 5. microvilli project sparsely into bile canaliculi
36
Q

What is the billiary tree?

A

system where bile flows from hepatocytes to gall bladder then intestine - smallest branches are canaliculi

37
Q

What are canaliculi?

A

formed by apposed grooves in the surface of adjacent hepatocytes

38
Q

What are intrahepatic ductules?

A

carry bile to hepatic ducts

39
Q

Name the components of the biliary tree?

A
  1. common hepatic duct 2. cystic duct 3. common bile duct
40
Q

What is the gall bladder?

A

concentrates and stores bile

41
Q

Describe the mucosa of the gallbladder?

A
  1. Consists of simple columnal epithelium 2. Epithelium has mucosa folds 3. Contains deep diverticula called Rokitansky-Aschoff sinuses
42
Q

Describe the epithelium of the mucosa?

A
  1. simple columnar cells 2. absorptive cells
43
Q

Describe the absorptive cells of the epithelium?

A
  1. Well developed apical microvilli 2. Localized concentrations of mitochondria 3. Lateral plications
44
Q

Describe the muscularis mucosa?

A

none

45
Q

Describe the submucosa?

A

none

46
Q

Describe the muscularis externa?

A

bundles of smooth muscle that are randomly orientated

47
Q

Describe the adventitia?

A

on the side that attaches to the liver

48
Q

Describe the serosa?

A

on the side that does not attach to the liver - has mesothelium

49
Q

The pancreas is divided into?

A
  1. head 2. body 3. tail
50
Q

Describe the course of the pancreatic duct (of Wirsung)?

A

extends through the length of the gland and empties into duodenum through hepatopancreatic ampullla (of Vater) which is surrounded by hepatopancreatic sphincter (of Oddi)

51
Q

The pancreas is made up of which components?

A
  1. The exocrine component is a compound gland that synthesizes and secretes enzymes for digestion in the intestine 2. The endocrine component synthesizes and secretes, into the blood, insulin and glucagon
52
Q

Describe the endocrine pancreas?

A

It is dispersed within exocrine component as distinct cell masses - islets of Langerhans : Constitute about 1-2% of the volume, and are most numerous in the tail.

53
Q

Name the major cells found in the endocrine pancreas?

A
  1. Beta cells 2. Alpha cells 3. Delta cells
54
Q

Describe beta cells?

A

They secrete insulin that lowers blood glucose - about 70% of the total cells

55
Q

Describe alpha cells?

A

They secrete glucagons that stimulates the release of glucose into the bloodstream - about 15-20 % of the total cells

56
Q

Describe delta cells?

A

They secrete somatostatin hormone that regulate somatotropin release from anterior pituitary gland - about 5-10% of the total cells

57
Q

Name minor cells of the endocrine pancreas?

A

Constitute about 5% of total cells - 1. PP (F) cells 2. D-1 cells 3. EC cells (enterochromaffin cells)

58
Q

Describe PP cels?

A

secrete Pancreatic polypeptide, that 1. stimulates gastric chief cells 2. inhibits bile + pancreatic secretion and intestinal motility

59
Q

Describe D-1 cells?

A

secrete Vasoactive intestinal peptide (VIP) that actions are similar to those of glucagon, and stimulates pancreatic exocrine secretion

60
Q

Describe EC cells? (enterochromaffin cells)?

A

secrete secretin stimulates 1. bicarbonate and pancreatic enzyme secretion 2. motilin (increases gastric and intestinal motility) 3. substance P (?)

61
Q

Describe the secretory acinus of the exocrine pancreas?

A
  1. Secretory units are acinar or tubuloacinar in shape 2. Formed by simple epithelium of pyramidal cells 3. The serous secretory cells secret digestive enzyme precursors 4. Cells contain zymogen granules which contain digestive enzyme precursors
62
Q

Describe the duct system of the exocrine pancreas?

A
  1. The initial duct (intercalated duct) begins within the acinus 2. The intercalated duct cells (squamous) located within the acinus are called centroacinal cells 3. Intercalated ducts add bicarbonate + water to exocrine secretion 4. Intercalated ducts drain into intralobular collecting ducts (Cuboidal epithelium) 5. Intralobular ducts drain into interlobular ducts( low columnal epithelium) - main pancreatic duct +/ accessory pancreatic duct

Gastrointestinal Tract Anatomy (7 decks)

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