Liver Anatomy and Histo

Question 1

Liver Blood Supply

Answer 1

• Both hepatic artery & portal vein
• Portal Vein (75%)
  
  • Receives blood from splenic, inferior mesenteric and superior mesenteric veins (low in oxygen but rich in nutrients and hormones)
• Divides into L & R branches; further divides
• Hepatic Artery (25%)
  
  • Usually off celiac trunk and able to adapt via arteriolar constriction/relaxation
  • Delivers highly oxygenated blood
  • Supplies portal tracts, supplies bile ducts, drains into sinusoids

Question 2

Portal Vein Collaterals

Answer 2

• Porto-portal (if extra-hepatic blockage - thrombosis, infection, malformation) - cystic, gastromental, diaphragmatic, paraumbilical
• *Drains toward liver (hepatopetal)
• Porto-systemic (if intrahepatic blockage- cirrhosis, fibrosis, carcinoma) - gastroesophageal, rectal, portorenal, paraumbilical
• *Drains away from liver (hepatofugal)

Question 3

Venous Drainage

Answer 3

Sinusoids –> terminal hepatic venules/central veins –> coalesce into middle/left/right hepatic veins –> IVC

Question 4

The Hepatic Lobule

Answer 4

• Hexagons separated by connective tissue septa w/ 6 portal triads on outside and central vein on inside
• Sinusoids move from portal triads –> central vein
• Carry portal vein and hepatic artery blood slowly past hepatocytes
• Large diameter, fenestrated, high capacitance/high compliance (can store a lot of blood by stretching)
• Portal Triad = connective tissue sheath (from Glisson’s capsule) filled w/ portal veins, hepatic arteries, bile ducts and lymphatic channels

Question 5

What constricts v. relaxes sinusoids?

Answer 5

• Vasoconstrict by: endothelin-1, angio II, thromboxane A2, epi
• Vasodialte by: NO, CO, H2S, PGI2

Question 6

Hepatic Arterial Buffer Response

Answer 6

• When dec flow in portal vein … adenosine builds up –> relax hepatic artery smooth muscle –> inc hepatic artery flow (to comp)
• When in flow in portal vein… adenosine wash out –> dec hepatic artery flow

Question 7

Liver Innervation

Answer 7

• Symp - bilateral fibers from T7-T10 in semilunar ganglion of celiac plexus
• Parasymp - R and L vagus and R phrenic
• Together form hepatic arterial plexus which surrounds arteries
• Arteries = symp only
• Bile ducts = symp and parasymp

Question 8

Biliary System

Answer 8

• Includes gall bladder, common hepatic duct, cystic duct, common bile duct (all outside liver)
• W/in liver… L and R hepatic bile ducts –> intrahepatic bile ducts –> interlobular hepatic ducts –> canals of Herring (terminal ducts) –> individual bile canaliculi (b/n adjacent hepatocytes on apical side)
• Blood supply from hepatic artery alone

Question 9

Cholangiocytes

Oval Cells

Answer 9

• Cholangiocytes (bile duct epithelial cells) secrete mucin and involved in hormone-regulated secretion of bile
• Oval Cells - at transition from canailuculi to small bile ducts; look like fetal hepatoblasts w/ potential to proliferate if disease

Question 10

Kuppfer Cells

Answer 10

• macrophages of the liver (phag, cytokines, APCs) and regulate hemodynamics, regulate protein synthesis and promote/inhibit disease modulators dep on status
• In sinusoids

Question 11

Space of Disse + What it Contains

Answer 11

• potential space b/n endothelial cells and hepatocytes - loosely arranged ECM and mult cells)
• Stellate Cells - store Vit A, make/secrete hepatic growth factors and collagen; can be made into myofibroblasts (fibrosis)
• Pit Cells - NK cells against viruses and tumor cells; also help regulate liver regeneration
• T/B immune cells
• Hepatocyte microvilli project into this space

Question 12

Hepatocytes

Answer 12

• Epithelial cells w/ mult apical and basal faces
• Apical - multiple; surfaces that face other hepatocytes; sealed w/ tight junctions; contains bile canaliculi
• Basal - faces hepatic sinusoids
• Contain mitochondria, RER and smooth ER
• Glycogen stored as clumps in cytoplasm (slightly bigger than a ribosome); dark clusters that can be stained w/ PAS

Question 13

Portal Triads on Histo

Answer 13

• Portal vein - endo (simple squamous) large lumen w/ thin smooth muscle
• Hepatic artery - endo (simple squamous) small lumen w/ thick smooth muscle (2-3 layers)
• Bile Duct(s)- can have multiple; simple cuboidal or simple columnar
• Lymph Vessel - very thin squamous epithelium w/ more irregular lumen