1 - Anatomy & Histology of the Liver Flashcards
Normal Liver Mass
1500g
Largest organ
Normal Portal Pressure
5 - 10 mm Hg
Low pressure
Hepatocytes - Do they all do the same thing?
No!!!!
They have functional heterogeneity
Liver’s borders
Right 5th rib
Left 6th rib
Right 9th rib
Feel it below the 9th rib and it’s HUGE!!!!!!
Contents of the portal vein
Collection of venous blood from spleen, splenic vein, SMA, IMA
Portal Hypertension
Obstruction to portal vein flow causing pressure to increase above 10mm Hg
Post-Hepatic Hypertension
Rarest kind of portal HTN
Congenital webs of the IVC
Intra-Hepatic Hypertension
Most common type of portal HTN
Cirrhosis
Other types of pathology
Pre-Hepatic Hypertension
Thrombosis blocking entry to the portal vein
How many lobes?
2!
Components of the liver
2 Lobes
Glisson’s Capsule (smooth! IT IS SMOOTH!!)
Falciform Ligament
Real divisions of the liver
8 Segments
4 on the left, 4 on the right
Each has its own vascular and biliary pedacle
Two sources of blood for the liver
Celiac Trunk > Hepatic Artery > Left & Right Lobes
Splenic Vein + IMA + SMA > Portal Vein
Biliary Tree
Bile conducted from ducts inside into common hepatic duct which meets with cystic duct to join the GI tract
Lobule
One functional unit of hepatocytes.
Central vein in the center
Arterial flow at the periphery
No connective tissue divisions between lobules the way pigs do!!!
Central veins
Marked by venous endothelium
Portal tracts
Collagen tracts that carry 3 tubes:
Bile duct
Artery
Vein
Can fibrose in pathways leading to other portal tracts when inflammation fucks that shit up
Blood path through a lobule
Portal tracts at periphery
Contents flow through sinudoids in the periportal regions
Undergo hella changes
Enter central veins to go back to the heart.
Bile Cannaliculi
Collect bile, interanastomose and form the canal of herring, which drains into the individual bile ducts that drain into the hilum and the common bile duct.
Where do the progenitor (stem) cells in the liver live?
The Canal of Herring
Description of Lobule
Radiating Cords
Nicely organized
Once Cell Thick (so nicely bathed)
Central Veins
Anastomose into Hepatic Veins (R & L)
Exit to IVC
Portal Tract on Histo
Nothing but collagen, fibroblasts and triad of structures
Inflammatory
Bile Duct
Tube of cuboidal epithelium
Limiting Plate
The hepatocytes at the edge of the Portal Tract
Chronic Hepatitis - Lymphocytes and inflammatory cells can infiltrate this structure and cause fibrosis
Mixing of Portal Venous and Hepatic Arterial Blood
Hepatic artery branches give off small twigs which empty arterial (oxygenated) blood into the periportal sinusoids directly outside the portal tract connective tissue
Chronic Hepatitis
Ground Glass Inclusions
Lymphocytes and other inflammatory cells cross limiting plate
Space of Disse
Type III Collagen
Discontinuous Array
Least oxygenated hepatocytes
Right around the central vein
They die quickly because they receive the least-oxygenated blood
Lipofuscin Pigment
Phagolysosomes with “Wear & Tear” cell debris
Brown Pigment Junk
Appears in Heart, Liver, and Adrenal. Myocytes particularly.
See it first in the hepatocytes surrounding central veins
Areas from Portal Tract to Central Vein
Periportal
Midzonal
Centrilobular
Each is about 7 cells wide
~22 hepatocytes from portal tract to central vein
Periportal Area - Zone 1
Best oxygen Oxygen tension is 65mm Hg Area where chronic hepatitis is most active Gluconeogenesis Bile Salt Synthesis
Centrilobular Area - Zone 3
Oxygen tension is 35 mm Hg Furthest from oxygen Most vulnerable to shock/ischemia Contains drug metabolizing enzymes Cytochrome p450s Area where alcohol is metabolized
Acinar Zones
Another interpretation of
Zone 1 - Best perfusion
Zone 2 - Midzonal
Zone 3 - Centrilobular
Zone 1
Chronic Hepatitis NH3 Metabolism (OTC & CPS Enzymes
Midzonal - Zone 2
Protein Synthesis
Zone 3
Drug Metabolism
Ischemia/Shock
Glutamine Synthetase Enzyme
Pit Cell
Natural Killer Cell
Tumor Surveillance
Tumor cells from GI tract come back in portal vein
Pit cells KILL THOSE BITCHES
Kupffer Cell
Macrophages
Contain multiple pseudopodia
Lie in waiting along endothelial surfaces
Phagocytose microbes
Endothelial Cells
Contain fenestrae in the sieve plate
Allow smallecules to move from Sinusoids into the Space of Disse
Space of Disse
Contains scattered discontinuous Collagen III fibers
Contains Ito (Stellate) cells
No basement membrane
Low pressure system (Dependent on how tight or loose the endothelial cells are, or how tight or loose stellate cells are
Stellate (Ito) Cells
Chief fibrotic source for the liver Stores vitamins Lies in wait for liver damage Releases collagen on damage Have little triangular basophilic nuclei (like little hats) over a vacuole of Vitamin A (fat soluble)
Canal of Hering
Bile canalliculi narrow to tubes lined by single cuboidal epithelium as they approach the bile ducts.
Progenitor cells live in that part
They can differentiate into whatever types of cells you need!!
Overdose of Vitamin A
Hyperplasia in Space of Disse
Endothelin and NO
Released in order to modify tension of endothelial cells and stellate cells
Bile Pumps
There are different bile pumps in the canaliculi
Studying these will reveal new forms of jaundice
BSEP
FIC-1
OATP
BSEP
Bile Salt Exporter Pump
Inhibited if you have septic shock from LPS
FIC-1
Familial Intrahepatic Cholestasis-1
Causes of jaundice in the liver itself
OATP
Organic anion transport pump
Cholestasis
Impaired bile secretion
Jaundice
Sallow yellow skin
Icteric sclera
LFTs
Liver Function Tests Total Protein Albumin Globulin Bilirubin Total Bilirubin Direct (conjugated) Bilirubin Indirect (unconjugated) AST ALT Alk Phos
Total Protein
6.7 - 8.6 g/dL
Albumin
3.5 - 5.5 g/dL
Globulin
2.0 - 3.5 g/dL
When a hepatocyte dies, what is released?
AST/ALT
Pressure on bile ducts and canaliculi?
Elevated Bilirubin/Direct bilirubin
Alk Phos goes up
GGT (gammaglutamyl transferase)
5’NT (5’ nucleotidase)
Synthesis
Synthetic proteins
Total Protein
Albumin
Synthesized in hepatocytes
Clotting Factors (I - II - V - VII - IX)
Albumin
Complement Proteins
Largest grey thing on EM
Erythrocytes
How does the liver regenerate?
Like medusa
How often do hepatocytes divide?
Every 400 Days
How many times can a hepatocyte divide?
70 Times
Regeneration after injury
Cell Division (eg hepatitis)
Severe Loss of tissue - Regeneration
From progenitor cells! (eg fulminant hepatitis)
Cirrhosis
An example of ABNORMAL REGENERATION with abnormally thick liver-cell plates
Cords are no longer 1 cell thick, but 3 or 4 cells thick
Blood can’t squeeze through!! THAT SUXXXX
Portal fibrosis
Embryonic origins of liver
Gut ectoderm
Septum transversum
Primitive diaphragm running horizontally
Gut from narrow tube growing into connective tissue plate
22 Days post-blastocyst
Foregut endoderm goes into septum transversum.
Vitelline veins go into sinusoids
26 days post-blastocyst
Cystic Bud
Cystic duct & gall bladder
7 - 8 weeks
Portal vein
Portal tract
Sinusoids
Liver cords (many cells thick)
9 - 10 weeks
Bile duct plates (BDP) develop
Differentiation of periportal hepatocytes to bile duct epithelium (bile duct plate)
23 weeks and later
Double-lined tube regresses, is remodeled, and disappears
One portion moves into the tract to become the intralobular bile duct
Some liver diseases affect this remodeling (Polycistic Liver Disease)
