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IMS: Microanatomy > Liver, Gallbladder, Pancreas > Flashcards

Liver, Gallbladder, Pancreas Flashcards

1
Q

Liver

Gross Anatomy

A
  • Four lobes: right, left, quadrate, caudate
  • Porta hepatis located in concave inferior surface
    • branches of hepatic portal vein and hepatic artery enter
    • right and left hepatic ducts exit
    • lymphatics leave
  • Dual blood suppy:
    • Hepatic artery proper
      • oxygenated blood
    • (Hepatic) Portal Vein
      • oxygen poor blood from GI tract, pancreas, and spleen
    • Sources mix at liver sinusoids
    • Leaves liver via hepatic veins
      • Near superior surface of liver
  • Covered by mesothelium except in 2 places:
    • where directly contacts gallbladder
    • bare area where mesothelium → underside of diaphragm
  • Glisson’s capsule
    • Dense irregular CT deep to mesothelium
    • continuous with capsule around vessels and bile ducts entering liver
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2
Q

Classic Liver Lobule

A

Based on venous drainage.

Region whose sinusoids all drain into same centrain vein.

  • Hexagonal in cross section
  • Portal triads located in portal canals @ each vertex
  • Central vein (terminal hepatic venule) @ center
  • Blood flows from periphery towards center
  • Bile flow from center out
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3
Q

Portal Triad

A
  • Located within portal canal
    • Enclosed by the limiting plate of hepatocytes
  • Components:
    • Hepatic artery/arteriole
    • Portal vein/venule
    • Bile duct (simple cuboidal epithelium)
    • Lymphatic capillaries often present
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4
Q

Central Veins

A

Terminal Hepatic Venule

  • Thin wall with endothelial cells but no smooth muscle
  • Plates of hepatocytes organized radially around central vein
  • Hepatic sinusoids run between plates
  • Receives blood from sinusoids
  • Drain into sublobular veins
  • Distinguished from portal triad because:
    • not accompanied by other vessels/ducts
    • less surrouding CT
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5
Q

Hepatic Sinusoids

A
  • Highly permeable sinusoidal capillaries
  • Wall formed by mixture of endothelial cells and Kupffer cells
  • Blood from inlet branches of hepatic artery and portal vein mixes here
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6
Q

Kupffer Cells

A
  • Hepatic resident macrophage
  • Contributes to sinusoidal walls
    • May extend across lumen
  • Phagocytize old/damaged RBC and particulates
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7
Q

Space of Disse

A
  • Narrow space encircling each sinusoid
    • Seperates it from hepatocytes
  • Microvilli of hepatocytes extend into space of Disse
  • Location of most metabolic exchange between blood and hepatocytes
  • Reticular fiber stroma located mainly here
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8
Q

Ito Cells

(Hepatic Stellate Cells)

A
  • Located in the space of Disse
  • Stores Vit A in cytoplasmic lipid droplets
  • Produces the reticular fiber stroma of liver
  • In cirrhosis, produce collagen type I causing fibrosis
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9
Q

Hepatic Blood Flow

A

Interlobular branches of hepatic artery & portal vein in portal canals →

Distributing branches leave portal canal & run between classic lobules →

Inlet vessels enter lobules →

Sinusoids →

Central vein →

Sublobuler vein →

Larger collecting veins →

3 or more hepatic veins →

IVC

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10
Q

Portal Lobule

A

Based on bile flow.

Region whose bile canaliculi all drain toward the bile duct in the same portal canal.

  • Roughly triangular in cross section
  • Central vein at each vertex
  • Portal triad in the center
  • Bile flows from periphery towards center
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11
Q

Hepatic Acinus of Rappaport

A

Based on gradients of O2, nutriends, and tonxins supplied by distributing vessels.

Used to explain patterns of hepatocyte metabolism and pathology.

  • Diamond shaped in cross section.
  • Central veins and portal triads located at the periphery.
  • Long axis connects 2 central veins
  • Short axis connects 2 portal triads
  • Distributing vessels lie on the short axis
  • Consists of 3 zones centered around the distributing vessels
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12
Q

Hepatocytes

A
  • Epithelial cells
  • Major parenchymal cell of the liver
  • LM:
    • Polygonal cells with round, euchromatic nuclei
    • One or more prominent nucleoli
    • Often binucleate or polypoid
  • Plasma membrane has 2 structurally and functionally different domains:
    • Sinusoidal domain
      • Contacts the space of Disse
      • Endocrine face
    • Lateral domain
      • Site where bile canaliculi form
      • Exocrine face
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13
Q

Bile Canaliculi

A
  • Formed from plasma membranes of adjacent hepatocytes
  • Tight junctions prevent bile leakage
  • Golgi, lysosomes, and residual bodies of hepatocytes often located near canaliculi
  • Lipofuscin may accumulate within residual bodies
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14
Q

Bile Ductules

A

Intrahepatic ductules, canals of Hering, cholangioles.

  • Found near the periphery of a classic lobule
  • Lined by simple cuboidal epithelial cells
  • Pierce the limiting place
  • Drains into interlobular bile ducts
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15
Q

Enterohepatic Recirculation

A
  • Bile salts recirculate between liver and small intestine
  • Pathway
    • Hepatocyte
    • Bile canaliculi
    • Bile duct system
    • Duodenum
      • Some lost in feces
    • Resoption into intestinal blood vessels
    • Hepatic portal vein
    • Hepatic sinusoids
    • Space of Disse
    • Hepatocyte
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16
Q

Deficiency of Bile Salts

A
  • Can lead to malabsorption of some fats
  • Results in steatorrhea
  • Precipitation of cholesterol in bile can lead to cholelithiasis
17
Q

Biliary Tree

A
  • Intrahepatic channels
    1. Bile canaliculi
    2. Bile ductules
    3. Interlobular bile ducts
  • Extrahepatic ducts
    1. Right and left hepatic ducts
      • Leave liver at porta hepatis
    2. Common hepatic duct
    3. Cystic duct from gallbladder
    4. Common bile duct
  • Common bile duct unites with the main pancreatic duct
  • Forms the ampulla of Vater
  • Empties into duodenum at the major duodenal papilla
    • sphincter of Oddi
18
Q

Gallbladder

Functions

A
  • Stores and concentrates bile
  • Releases stored bile via cystic duct into common bile duct
    • CCK main stimulus for bile release
      • Secreted by I cells in intestinal mucosa
        • In response to dietary fat in intestine
19
Q

Gallbladder Wall

A

Has a mucosa, muscularis, and serosa/adventitia.

No muscularis mucosae or submucosa.

  • Mucosa
    • Simple columnar epithelium
      • mainly absorptive cells
      • lateral spaces between absorptive cells widen when actively concentrating bile
    • Lamina propria
    • Unless gallbladder is full, mucosa usually has many deep irregular folds
  • Muscularis
    • Circular near neck of bladder
    • More irregular in body
  • Serosa/Adventitia
    • Adventitia is present where gallbladder directly contacts liver
    • Serosa covers remainder of the organ
20
Q

Rokitansky-Aschoff Crypts

A
  • Deep invaginations of the epithelium
  • Extends into or through muscularis
  • Found in the gallbladder with chronic inflammation
  • May perforate
21
Q

Pancreatic Acinar Cells

A
  • Pyramid-shaped serous cells
  • Secrete wide variety of digestive enzymes zymogens
    • Trypsinogen
    • Chymotrypsinogen
    • Procarboxypeptidase
  • Basal basophilia due to extensive RER
  • Acidophilic zymogen granules in apical cytoplasm stores enzymes
  • Exocytosis occurs in response to signals
    • CCK
    • ACh from vagal fibers
22
Q

Centroacinar Cells

A
  • Pale, low cuboidal cells
  • Unique to the pancreas
  • Lies within the lumen of a secretory acinus
  • Represents the first cells in an intercalated duct
    • Intra-acinar portion
23
Q

Pancreatic

Intercalated Ducts

A
  • Smallest type of intralobular duct
  • Simple, low cuboidal epithelium
  • Secretes a watery bicarbonate-rich fluid
    • In response to secretin
      • Hormone produced by S cells in duodenum
  • Drains into larger intralobular ducts
24
Q

Pancreatic Ductal System

A
  • Centroacinar cells → first cells in an intercalated duct
  • Intercalated ducts
  • Larger intralobular ducts
    • Lined by simple cuboidal epithelium
    • No basal striations
      • No striated duct in the pancreas
    • Empty into interlobular ducts
  • Interlobular ducts
    • Run in the CT septa
    • Empty into the main pancreatic duct
  • Main duct
    • Units with common bile duct
    • Form the ampulla of Vater
    • Empties into duodenum at the major duodenal papilla
25
Q

Islets of Langerhans

A
  • Endocrine portion of the pancreas
  • Spherical structures scattered among acini
    • Most islets larger than a secretory acinus
    • Usually paler staining
  • Highly vascularized with fenestrated capillaries
  • Cells appear more irregularly arranged
    • Not structurally polarized
26
Q

𝛽-cells

A
  • Most abundant cell in islets of Langerhans
  • Main product is insulin
  • Also produce other hormone
    • Amylin appetite suppresant
  • Located throughout islet in humans
  • Secretory granules may have dark angular “crystalline” core
27
Q

𝛼-cells

A
  • Produce glucagon
  • Mainly located at the periphery of an islet
  • Granules have a dark spherical core surrounded by a clear halo
28
Q

𝛿-cells

(Delta)

A
  • Produce somatostatin
  • Functions to inhibit:
    • gut motility
    • gallbladder secretions
    • secretions by acinar cells
    • secretions of insulin and glucagon
  • Granules are light-staining & almost completely filled with secretory material
29
Q

PP (F) Cells

A
  • Produce pancreatic polypeptide
    • Inhibits secretion by acinar cells and duct cells
    • Stimulates gastric chief cells
30
Q

Zollinger-Ellison Syndrome

A
  • Pancreatic tumor cells produce excess gastrin
  • Cause excessive acid secretion from the stomach
  • Leads to ulcers
  • Gastrin produced transiently in islets during fetal life.
31
Q

Epsilon Cells

A

Produce Ghrelin → appetite suppresant

32
Q

Insuloportal System

(Islet-acinar Portal)

A

Venous portal system within the pancreas.

Carries islet hormones that affect activity of other islet cells or acinar cells.

  • First capillary bed within islets
    • Fenestrated
    • Blood flows from periphery to center of an islet
  • Venules drain first capillary bed
  • Secondary capillary bed supplies acini
    • Continuous
    • Acinar cell activity can be modulated by islet hormones

IMS: Microanatomy (16 decks)

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