Functional microanatomy of the liver

Question 1

general anatomical features of the liver

Answer 1

large, lobulated exocrine and blood processing gland, with vessels and ducts entering and leaving at the porta
enclosed by a thin collagen tissue capsule, mostly covered by the mesothelium
collagen tissue of the branching vascular system provides gross support
parenchymal cells are supported by fien reticular fibres

Question 2

what does the internal structure of the liver evolve around

Answer 2

several vessels entering or leaving the organ

Question 3

portal vein

Answer 3

brings food rich blood from the gut

Question 4

hepatic artery

Answer 4

bring arterial blood

Question 5

hepatic veins

Answer 5

takes away processed blood into vena cava

Question 6

lymphatics

Answer 6

take away lymph

Question 7

hepatic ducts

Answer 7

remove bile to gallbladder and gut

Question 8

liver blood supply

Answer 8

25% from hepatic artery - arterial
75% from portal vein - food rich from gut

Question 9

nerve supply of liver

Answer 9

sympathetic and parasympathetic supply of perivascular structures, very little and sinusoidal level

Question 10

first impression of liver microanatomy

Answer 10

uniform mass of large glandular cells throughout liver substance

Question 11

closer examination of liver microanatomy

Answer 11

cells arranged in perforated plates, one cell wide
between plates are sinusoidal blood channels lined by endothelial cells

Question 12

what are scattered in the glandular mass

Answer 12

blood vessels, both alone and accompanied by other vessels
distribution of these vessels defines or marks out classic hepatic lobules

Question 13

central vein/terminal hepatic venule

Answer 13

very thin wall
lies in centre of lobule with sinusoids converging towards and opening into it

Question 14

sublobular/intercalated vein

Answer 14

thicker wall
lies alone at periphery of lobule

Question 15

branch of portal vein

Answer 15

at periphery of lobule
accompanied by one or more small hepatic arteries/arterioles, one or more bile ducts/ductules lined by cuboidal epithelium, and lymphatics

Question 16

what constitutes a portal triad

Answer 16

portal vein, artery and bile duct - the area which they lie in is a portal area

Question 17

hepatic lobular blood flow is what 3 things

Answer 17

1 - from branches of portal vein and hepatic artery, from periphery towards centre
2 - in the sinusoids between cell plates
3 - blood collected in central veins goes to sublobular veins, then to collecting veins, and then hepatic veins leaving the liver

Question 18

what is intralobular bile flow

Answer 18

from the lobules centre towards the peripheral bile ducts, and runs within any one cell plate, between the liver cells in bile canaliculi

Question 19

liver acinus

Answer 19

represents as a functional unit comprising parts of 3 or so lobules. explains the differences in exposure to the blood supply among various parts of lobules

Question 20

what zones are the liver acini divided into

Answer 20

1 - periportal
2 - intermediate
3 - perivenous (close to the central vein)

Question 21

features of the periportal zone of the liver acinus

Answer 21

roughly spheroid
isolated from periportal zones of adjacent acini

Question 22

current concepts of hepatic microarchitecture

Answer 22

1 - primary lobule territory
2 - anatomical details: conical 3D configuration

Question 23

what are liver sinusoids

Answer 23

low pressure vascular channels that receive blood from terminal branches of the hepatic artery and portal vein at the periphery of lobules and deliver it into central veins

Question 24

what are sinusoids lined with

Answer 24

fenestrated epithelial cells which are loosely attached. they hold phagocytic Kupffer cells

Question 25

how are fenestrated epithelial lining cells attached

Answer 25

loosely attached, rest of microvilli of underlying hepatic cells, without basal lamina intervening

Question 26

what is formed by fenestrated epithelial lining cells and what does this result in

Answer 26

forms a sieve plate. means plasma can pass through into perisinusoidal space of Disse to interact with hepatocytes. some fluid may pass to periphery of lobule to be collected as lymph

Question 27

what does Disse's space contain

Answer 27

ECM material, no visible basal lamina

Question 28

function and location of stellate cells

Answer 28

scarce, fat storing lie outside endothelial cells store vitamin A respond to variety of insults by making collagen and causing cirrhosis (fibrosis)

Question 29

what 3 things does the sinusoidal wall provide for

Answer 29

1 - blood cleansing, e.g. of gut bacterial toxins 2 - haemopoiesis in the embryo 3 - bringing plasma into intimate contact with hepatic cell for many metabolic functions of storage, transformations, syntheses, regulation of plasma concentration, detoxification, production of bile, and assisting defence by producing acute-phase proteins

Question 30

what are hepatocytes

Answer 30

the main functional cell of the liver. 80% of liver mass

Question 31

3D arrangement of hepatocytes

Answer 31

arranged in plates that anastomose with each other polygonal in shape, sides in contact with either sinusoids of neighbouring hepatocytes

Question 32

what forms bile canaliculi

Answer 32

modified portions of the lateral faces of hepatocytes. microvilli present abundantly on sinusoidal faces and project sparsely into bile canaliculi

Question 33

hepatocyte nuclei

Answer 33

distinctly round, with one or two prominent nucleoli. majority have single nucleus but binucleate cells are common

Question 34

features of hepatocytes/hepatic cells

Answer 34

large spheroid nucleus with membrane pores and ribosomes on outer membrane extensive granular ER smooth ER mitochondria actin and other filaments near bile canaliculi and elsewhere cell membrane projecting microvilli into space of Disse - held firmly to adjacent cells Golgi body and lysosomes lying near canaliculis peroxisomes glycogen granules stored in association with smooth ER fat droplets occurring briefly after meals lipofuscin or aging pigment

Question 35

granular endoplasmic reticulum

Answer 35

protein synthesis for enzymes, plasma proteins, etc

Question 36

smooth endoplasmic reticulum

Answer 36

steroid hormone and cholesterol metabolism, lipids taken in, processed and secreted in a way very like enterocytes, SER carries enzymes for detoxification

Question 37

mitochondria

Answer 37

oxidative and other enzymes

Question 38

system of canaliculi

Answer 38

between hepatic cells leads to canals of hering/cholangioles both have hepatocytes and bile duct cells in their walls

Question 39

bile ducts

Answer 39

epithelium changes to columnar mucous cells and extrahepatically the ducts acquire smooth muscle as well as collagen tissue

Question 40

cystic ducts

Answer 40

allow reflux into gallbladder when sphincter of Oddi at duodenal outlet of the common bile duct is closed

Question 41

bile pathways

Answer 41

system of canaliculi > canals of hering/cholangioles > bile ductules > bile ducts > cystic duct

Question 42

features of bile ductules and where they are found

Answer 42

in portal areas small cuboidal cells firmly held by membrane interdigitations and junctional complexes few luminal microvilli

Question 43

formation of lymph

Answer 43

formed by filtration of plasma into spaces of Disse as blood flows through sinusoids lymph percolates between space of Disse and portal tracts then lymphatics form that run along portal vessels and biliary ducts