Liver

Question 1

major functions of the liver.

Answer 1

1. Absorption and processing: carbs, proteins, lipds
2. synthesis and endocrine secretion: plasma p, coagulation factors, metals, lipid transport proteins, cholesterol
3. detox and degredation
4. conversion, modification of hormones
5. phagocytosis of antigens, old RBC by Kupffer cells
6. exocrine secretion of bilirubin, bile salts

Question 2

What encloses the liver?

Answer 2

dense irregular connective tissue and a layer of mesothelium

Question 3

What is at each corner of a lobule?

Answer 3

portal canal …

portal “triad” = hepatic portal vein, hepatic artery, bile duct, lymphatic, nerves

Question 4

describe blood flow

Answer 4

portal vein branches over lateral surfaces –> distributing veins –> inlet venules

hepatic artery branches over lateral surface –> distributing arteries –> inlet arterioles

blood mixes and enters central vein then sublobular vein then hepatic vein

Question 5

what supports each lobule?

Answer 5

connective tissue…

within lobule is reticular fiber (coll III)

(also connective tissue in portal canal that supports liver)

Question 6

describe the 3D structure of a lobule

Answer 6

six lateral faces

two basal faces

single apex

Question 7

Name the cells in the sinusoids and their function

Answer 7

1. kuppfer cells - phagocytose antigens and old RBC
2. pit cell - NK innate immune system lymphocyte
3. endothelial cells - fenestrations/discontinuous allows plasma to move into space between hepatocytes and sinusoids.
4. lipcytes - lipid droplets that store vitA (essential but can be toxic)

Question 8

Structure function of space of Disse

Answer 8

filled with only blood plasma (no RBC or platelets)

reticular fibers support walls of sinusoids

nutrients absorbed by microvilli at hepatocyte base

endocrine p secretions

Question 9

Surfaces of hepatocyte?

Answer 9

two basal surfaces - microvilli for absorption, secrete endocrine products,

6 lateral surfaces - secrete endocrine products, uptake of nutrients

apical surface - 1/2 of bile canaliculus, excocrine secretion of bile

Question 10

Bile flow?

Answer 10

bile canaliculi into bile ductules into canals of Hering…

merge and form bile ducts in the portal canals into gall bladder then into small intestine…

all this called the biliary tree

Question 11

linings of canals of Hering?

Answer 11

simple cuboidal epithelium.

maybe stem cells for liver regeneration.

liver cells divide infrequently, but when damaged rapid mitosis occurs.

Question 12

cells that line biliary tree post-canal of Hering?

Answer 12

cholangiocytes

Question 13

cell surface of hepatocytes?

Answer 13

sides of bile canaliculus lines with junctional complex (tight junction, adhesion belt, spot desmosomes)…

hold apical and lateral surface together…

microvilli on apical surface

Question 14

8 organells of hepatocyte?

Answer 14

1. RER - membrane and secreted p synthesis (albumin, protein component of lipoprotein)
2. SER - lipid syn of lipoproteins; detox of ammonia, alcohol, anesthetics; syn/deg of glycogen (assoc. with SER)
3. mitos - energy
4. Golgi - mostly near bile canaliculus for bile secretion, others by sinusoids for proessing/packaging of secreted p
5. peroxisomes - H2O2 breakdown, ethanol oxidation, alcohol dehydrogenase
6. lysosomes - breakdown of endocytosed substanced and organells, Fe storage
7. Terminal web - apical. actin, myosin, other p. actin and mysoin interaction allows for contractions along canaliculi to move bile toward portal canal.
8. lipid droplets - cholesterol and lipop storage

Question 15

liver anicus layout

Answer 15

2 central canals and 2 portal canals (like two triangles)

Question 16

3 zones of liver acinus

Answer 16

Zone 1 - blood rich in O2, nutrients; syn. glycogen and plasma p; last to die

Zone 2 - blood has less O2, nutrients

Zone 3 - blood very low in O2, nutrients; alcohol, drug detox; central necrosis (cell death near central canal); first to show steatosis (fat accumulation from reduced blood flow)

Question 17

secretions in bile

Answer 17

bile salts, bile pigments, cholesterol, phospholipids, electrolytes

Question 18

enterohepatic circulation?

Answer 18

bile substance produced by hepatocytes –> released to duodenum –> recovered in ileum (some secreted in feces) –> enters intestinal capilaries –> follows portal vein to liver

Question 19

function of bile?

Answer 19

emulsify lipids in small intestine

keep cholesterol and phospholipids of bile in solution

Question 20

RBC breakdown and bilirubin?

Answer 20

RBC breaksdown giving bile pigments (mainly bilirubin)

heme broken down by macrophages in spleen and Kupffer cells in liver

hepatocytes transport bilirubin into the bile and is released in feces

Question 21

clinical relevance of bilirubin?

Answer 21

jaundice:

accumulation of bilirubin in blood and tissues

skin and sclerae appear yellow

from…overactive destruction of erythrocytes, impaired bilirubin processing, inadequate bile draining from obstruction

Question 22

three layers of gall bladder and structure

Answer 22

1. mucosa - epithelium, lamina propria
2. muscularis externa - random arrangement of smooth muscle
3. fibrosa or serosa contain large blood vessels, lympathics, adipose tissue

Question 23

GB mucosa epithelium and lamina propria

Answer 23

epithelium - simple columnar epi with microvilli; apical junctional complexes, mitos; lateral interdigitations

lamina propria - loose connective tissue, fenestrated capillaries, small venules, lymphocytes, plasma cells

Question 24

fibrose vs. serosa

Answer 24

fibrosa - where gallbladder attached to liver, no intervening peritoneum

serosa - parts where GB covered peritoneum (mesothelium)

Question 25

function of gall bladder

Answer 25

stores and concentrates bile

~ 50 ml

bile secreted by liver, enters GB via cystic duct

Question 26

how is bile concentrated?

Answer 26

selective absoption of water and sodium by epithelium

most water enters fenestrated capillaries in mucosa, some enter lymphatics of fibrosa/serosa

Question 27

bile delivery to duodenum

Answer 27

GB contraction…

1. fat triggers cholecystokinin secretion by enteroendocrine cells in duodenum
2. hormone enters blood
3. causes GB to contract, sphincters to relax