L35: Hepatic physiology

Question 1

what organ has the greatest regenerative capacity

Answer 1

liver; it is able to regenerate

Question 2

what are the 2 blood sources of the liver

Answer 2

• hepatic artery from the aorta (provides O2)
• hepatic portal vein from the GI tract (provides nutrients)

Question 3

where does the hepatic portal vein collect blood from

Answer 3

stomach, SI and part of LI
takes nutrients and delivers it to the liver

Question 4

most of the liver blood is ____ blood

Answer 4

venous
increases after a meal

Question 5

through what vein does blood leave the liver

Answer 5

heaptic vein

Question 6

what are the functional units of the liver

Answer 6

lobules = hexagonal tissue surrounding a central vein

Question 7

what is the role of Kupffer cells

Answer 7

destroy old RBCs and bacteria
get exposed to large volumes of blood

Question 8

Vitamin A is stored as ____ in ?

Answer 8

retinol
hepatocytes or stellate cells

Question 9

what is the space of disse

Answer 9

space b/w hepatocytes and sinusoids
fills w/ collagen = fibrosis

Question 10

what is the portal triad

Answer 10

the 3 vessels in a lobule that drain into a central vein
- bile duct
- hepatic artery
- portal vein

Question 11

blood enters the sinusoids from the _____ vein and the ____ artery

Answer 11

portal vein and hepatic artery

Question 12

what are the different zones in the lobule

Answer 12

periportal hepatocytes (zone I)
centrilobular (pericentral, zone II)
hepatocytes (zone III)

Question 13

what is responsible for the variability in activity of each zone of the lobule

Answer 13

heterogeneity of O2 supply

Question 14

what zone of the lobule is highest in O2

Answer 14

zone I
* has many mitochondria
* oxidative metabolism
* bile acid secretion
* glycogen and other nutrient storage

Question 15

what lobule zone is responsible for bile acid secretion

Answer 15

zone I

Question 16

what lobule zone is concerned w/ oxidative metabolism (FA oxidation, gluconeogenesis, urea genesis)

Answer 16

zone I

Question 17

what zone is the transition zone

Answer 17

zone II

Question 18

What lobule zone is lowest in O2 and therefore anaerobic metabolism occurs here

Answer 18

zone II

Question 19

in what zone of the lobule does biotransformation of drugs/chemicals/toxins occur

Answer 19

zone III

Question 20

what zone is most sensitive to damage caused by ischemia

Answer 20

zone III - least O2 supply
most susceptible to centrilobular necrosis, hypoxia, congestion

Question 21

what is centrilobular necrosis and what zone does it usually occur

Answer 21

necrosis around the central vein
zone III

Question 22

what are the 2 capillary beds blood runs through before it returns to the heart

Answer 22

• mesenteric
• portal

Question 23

what drives blood through the portal capillary bed

Answer 23

• pressure in portal vein being higher than in the hepatic sinusoids (precapillary resistance in portal inflow is low)
• central vein of liver is large so resistance is low
• venous outflow of the liver goes into thoracic vena cava

Question 24

what is the consequence of right sided heart failure on the liver?

Answer 24

it increases vena cava pressure which leads to reduced blood flow from the intestine
excess interstitial fluid leaks into edematous tossie and accumulates in the peritoneal cavity (ascites)

Question 25

what can cause necrosis of zone 1 (periportal)

Answer 25

* phosphorous poisoning (rat poison, fertilizer, fireworks) * eclampsia (sudden pregnancy/postpartum seizures)

Question 26

what can cause necrosis of zone 3 (centrilobular zone)

Answer 26

* ischemic injury * toxic effects * carbon tetrachloride exposure * chloroform ingestion

Question 27

what liver enzymes are most likely elevated when there is an increase in cell membrane permeability or death

Answer 27

* alanine transaminase (ALT) * asparate transaminase (AST) * alkaline phosphatase (ALP) * gamma glutamyl transpeptidase (GGT)

Question 28

elevated liver enzymes may indicate?

Answer 28

inflammed or damaged liver cells b/c they leak higher than normal amounts of enzymes into the bloodstream which can result in elevated liver enzymes in a blood test

Question 29

why does a decreased uptake and conversion of ammonia into urea cause high ammonia concentrations

Answer 29

high ammonia concentration in urine are followed by low urea nitrogen concentration and PU/PD b/c urine concentrating ability depends on medullary interstitial tonicity which is generated by urea and NaCl

Question 30

what is the function of bile

Answer 30

* excretory route for solutes that aren't excreted by the kidney * bile salts and acids are needed for lipid digestion and absorption

Question 31

what is the composition of bile

Answer 31

* bile salts (50%) * phospholipids (40%) * bilirubin, electrolytes, water

Question 32

bile is continuously secreted by ____ into _____

Answer 32

hepatocytes into canaliculi

Question 33

where are bile caniculi located

Answer 33

b/w adjacent hepatocytes, they drain into bile ducts at the periphery of lobules

Question 34

what are the 2 primary bile acids

Answer 34

* cholic acid * chenodeoxycholic acid

Question 35

what does the liver conjugate bile acids w/

Answer 35

Taurine and glycine

Question 36

what are the 2 secondary bile acids and how are they formed

Answer 36

deoxycholic and lithocholic acid primary bile acids that get dehydroxylated by bacteria into secondary bile acids

Question 37

bile salts are derivates of ?

Answer 37

cholesterol

Question 38

what happens to bile salts after they are used in fat digestion and absorption

Answer 38

they get reabsorbed into the blood through an active transport mechanism in the distal ileum and by passive absorption throughout the intestine

Question 39

what are the sites at which bile salts get reabsorbed

Answer 39

* distal ileum (via active transport) * throughout the intestines (passive abs)

Question 40

after being reabsorbed how do bile salts get back to the liver

Answer 40

hepatic portal system = enterophepatic circulation

Question 41

is bilirubin involved in digestion

Answer 41

no but excreted in bile