Term
| What percentage of adult body weight is comprised of the liver? |
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Definition
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Term
| Tell me about the blood supply of the liver and how it flows. What makes the liver more vulnerable to hypoxia than most organs? |
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Definition
Only 30% of blood supply is from the hepatic artery (fully oxygenated blood from left ventricle). The remaining 70% is poorly oxygenated blood via the portal vein from the gut.
Blood flows from hepatic arterioles and portal venules in the triads through the sinusoids to the central vein, which drains the liver. |
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Term
| What does a portal triad contain? Where in the hepatic lobule is it found? |
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Definition
| Hepatic arteriole, bile duct, portal venule. Found at lobule periphery. |
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Term
| Describe hepatic lobular zones. |
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Definition
Zone 1: at outside, nearest blood supply (portal triad is at outside of lobule). Receives toxins, etc. from portal vein first, so usually more susceptible to toxic injury.
Zone 2: intermediate
Zone 3: at inside, surrounding central vein. Most susceptible to hypoxic injury. |
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Term
| Describe the organelles found in Zone 1 vs. Zone 3 hepatocytes. |
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Definition
Zone 1: more mitochondria and rough ER.
Zone 3: fewer mitochondria and rER; more smooth ER and peroxisomes. |
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Term
| What kind of cells line the sinusoids? What is the sinusoidal "lumen" and what does it contain? |
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Definition
| Endothelial cells (fenestrated/discontinuous) line the sinusoids. The lumen contains Kuppfer cells and Pit cells (function unknown). |
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Term
| What are the different specialized regions of the hepatocyte plasme membrane? |
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Definition
Sinusoidal region (40%): microvilli
Canalicular region (15%): also contain microvilli; allows passage of bile constituents made by hepatocytes
Lateral and junctional regions: tight junctions/desmosomes |
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Term
| What abnormality do you see in blood Alkaline Phosphatase in cholestasis, and why? |
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Definition
| Alk Phos is found at the canalicular region. When cholestasis results in leaky/damaged membranes, Alk Phos is released and blood levels are elevated as a result. |
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Term
| What are hepatic stem cells called, where are they found, and how can they be visualized? |
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Definition
| Oval cells; found in portal zone; stain with cytokeratin. |
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Term
| What percent of liver mass can mammals afford to lose? Does it grow back (how soon?)? |
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Definition
Can lose 75%.
Cell numbers regenerate within a week. |
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Term
| What are Stellate cells, what is their other name, and what do they do? |
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Definition
a.k.a. Ito cells. 5% of liver cell population.
Store and metabolize vitamin A.
Produce collagen and other ECM components (role in hepatic inflammation & fibrosis). |
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Term
| Does the liver have many or few immune cells? Why? |
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Definition
Many. Can be considered immune organ. Kuppfer cells, NK cells, T cells, liver endothelial cells.
Needs immune surveillance b/c of high amounts of bacterial endotoxin, etc. arriving from gut. |
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Term
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Definition
| In hepatocytes, at the bile canalicular membrane. Transported from there to bile ducts at portal triads. |
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Term
| What type of cells line the bile ducts? |
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Definition
| Cuboidal epithelium (or columnar in the larger ducts). |
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Term
| What species lack a gall bladder? |
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Definition
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Term
| Describe histological layers of gall bladder. |
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Definition
Mucosa with prominent folds (distendable; columnar epithelium).
Connective tissue (lamina propria)
Inner and outer smooth muscle layers
Serosal surface |
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Term
| What is the normal lifespan of a hepatocyte? |
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Definition
| 1 year! This means turnover is slow and generally only 1 in 20,000-40,000 hepatocytes is undergoing mitosis. |
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Term
| Where is the Space of Disse? |
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Definition
| Between the sinusoid (lined with endothelial cells, since a sinusoid is basically a liver capillary) and the hepatocytes is the Space of Disse. In the SoD lie Stellate cells. |
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