The Liver

Question 1

What is the basic funcitonal unit of the liver?

Answer 1

Liver lobule

Question 2

What are the resident macrophages in the liver and what is their function?

Answer 2

Kupffer cells (reticuloendothelial cells) that line the venous sinusoids. Phagocytize bacteria and other foreign material in hepatic sinus blood.

Question 3

What effect does cirrhosis have on blood flow through the liver?

Answer 3

Greatly increases resistance. In the healthy liver, pressure in portal vein is 9mmHg, and hepatic vein is 0mmHg creating little resistance of blood flow through the liver. In cirrhosis, liver parenchymal cells are destroyed and replaced with firbous tissue that contracts around blood vessels impeding flow of portal blood.

Question 4

Causes of cirrhosis of the liver?

Answer 4

Excess fat accumulation (resulting in inflammation), toxins, viral diseases (infectious hepatitis), obstruction or infection in the bile ducts.

Question 5

Liver regeneration via cell division and growth is controlled by what growth factor?

Answer 5

Hepatocyte growth factor. Produced by mesenchymal cells in liver and other tissues (not by hepatocytes).
Other growth factors that may play a role: EGF, cytokines TNF and IL-6

Question 6

Once a liver has restored itself to it’s original size, hepatic cell division ceases and though the process is not poorly understood, the most likely terminator of liver regeneration is:

Answer 6

Transforming growth factor B (TGF-B). A cytokine secreted by hepatic cells and is a potent inhibitor of liver cell proliferation.

Question 7

What is the glucose buffer function of the liver?

Answer 7

The livers ability to maintain normal BG concentration. Liver removes excess glucose from blood, stores as glycogen, and returns to blood when concentration is too low.

Question 8

What is gluconeogenesis?

Answer 8

When glucose concentration falls below normal, amino acids and glycerol from triglycerides are converted into glucose.

Question 9

80% of cholesterol synthesized in the liver is converted into:

Answer 9

Bile salts which are then secreted into bile.

Question 10

Aside from gamma globulins, almost all plasma proteins are formed by what cell in the liver?

Answer 10

Hepatic cells.

Question 11

The vitamin stored in greatest quantity in the liver is_____? What other vitamins are stored in the liver?

Answer 11

Vit A (can store 10 months worth)
Vit D and Vit B12. (can store 3-4 mo, 1+ years worth)

Question 12

Outside of hemoglobin the blood, the liver stores a large portion of the body’s iron in the form of_____. Which protein do hepatic cells contain to combine reversibly with iron?

Answer 12

Ferritin,

Apoferritin.

Question 13

Which blood coagulation substances are formed in the liver?

Answer 13

fibrinogen, prothrombi, accelerator globulin, factor VII. Vit K is required for the formation of these (particularly prothrombin and factors 7, 9 and 10).

Question 14

How does the liver contribute to calcium excretion from the body?

Answer 14

Liver secretes calcium into bile which is then passed into the gut and lost through feces.

Question 15

Normal plasma bilirubin is approximately 0.5mg/dl. When this rises above ______ the skin and body can begin to look jaundiced.

Answer 15

1.5 to 2

Question 16

What are two of the most common causes of jaundice?

Answer 16

RBC hemolysis, obstruction of bile ducts (gallstone, neoplasia) or damage to liver cells (hepatitis) so that normal bilirubin amounts cannot be excreted into GI tract.

Question 17

With obstructive jaundice, is the bilirubin in the plasma typically conjugated or unconjugated?

Answer 17

Conjugated. Unconjugated bilirubin still passes into liver cells and becomes conjugated, but rather than passing into the SI it is directly emptied into lymph leaving the liver from rupture or congested bile caniliculi.

Question 18

In hemolytic jaundice, bilirubin is usually in the conjugated or unconjugated form?

Answer 18

Unconjugated