Week 4: liver and gallbladder Microanatomy

Question 1

trace pattern of blood circulation in the liver

Answer 1

-blood from 2 sources
1. portal triads-25%
-hepatic artery branches into interloper arteries, interlobular arteries, hepatic arterioles, sinusoids, and ventral veins
2. Portal veins, 75%
-portal veins to interlobar veins, interlobular veins, hepatic venules, sinusoids, and central veins
Outflow
-from central veins to sub lobular veins to hepatic veins

Question 2

3 ways to see lobules of liver

Answer 2

1. classic lobules
   - hexagonal with central vein in middle and portal triads at angles (portal triads contain branches of portal vein, hepatic artery, lymphatics, bile ducts)
   - based on histology
2. Portal lobules
   - triangular, contains 3 classic lobules
   - center is portal triad, apices are central veins
   - emphasizes bile flow
3. Hepatic acini or Rappaport lobules
   - diamond shaped
   - apices are central veins
   - divided into zones, Zone 1 at center and zone 3 at peripheries next to central veins
   - based on blood flow. Zone 3 cells most impacted by hypoxia, zone 1 cells first exposed to toxic substance carried by portal veins1

Question 3

Components of hepatocyte plate

Answer 3

1. hepatocytes: for synthesis, detox, storage
2. sinusoids: lined by thin fenestrated epithelium
3. Space of diss: between hepatocytes and basal surface of endothelial cells
   - Kupffer cells (macrophages) project into sinusoid
   - microvilli from hepatocytes in this space
4. stellate (Ito) cells: in space of Disse. storage for Vit A, fat, type II collagen
5. Bile canaliculi: small channels formed between neighboring hepatocytes
   - bile flows to intralobular bile ductules (canals of Hering)

Question 4

Gallbladder wall layers

Answer 4

1. Mucosa: simple columnar epithelium
   - richly vascularized lamina propria
   - mucosa had convoluted folds, no villi, when empty
   - No goblet cells, no submucosa, no muscularis mucosa
2. Muscle layer
   - thin layer of SM cells, in oblique fashion
3. Connective tissue layer
   - dense irregularCT, nerves, and vessels
4. Serosa: covers gallbladder and adventitia where gallbladder attached to the liver

Question 5

Gallbladder function

Answer 5

-collects, concentrates, stores, and releases bile to the duodenum