Microanatomy 2

Question 1

list the major functions of the liver

Answer 1

Detoxification of metabolic waste products.

Destruction of used red blood cells and reclamation of their constituents.

Synthesis and secretion of bile which facilitates the absorption of fats and is essential for the absorption of fat-soluble vitamins. The addition of pigments to bile is a mechanism whereby the liver eliminates some waste products of spent red blood cells.

Synthesis of plasma lipoproteins.

Metabolic functions, e.g. glycogen synthesis, gluconeogenesis and storage of glycogen, some vitamins, iron and lipid.

Detoxification of various drugs and toxins, e.g. alcohol.

Question 2

what is the blood supply of the liver

Answer 2

• the liver has both arterial and venous blood supplies
• absorbed food products pass directly from the gut to the liver via the hepatic portal vein
• oxygen required for liver metabolism is supplied through the hepatic artery
• venous drainage occurs by the way of the hepatic vein

Question 3

what are hepatocytes

Answer 3

These are parenchymal cells that form plates. They are the main functional cells of the liver.

Question 4

what are sinusoids

Answer 4

These are the wide vascular channels that separate the plates of hepatocytes.

The majority of cells lining the sinusoids are endothelial cells.

However, scattered among these cells are specific macrophage type cells termed Kupffer cells. These are part of the liver’s defence system.

Question 5

what are bile ducts

Answer 5

These carry bile from the hepatocytes eventually into the duodenum.

Bile is produced in hepatocytes and is secreted into a network of minute bile canaliculi (no discrete structure of their own) positioned between plasma membranes of adjacent hepatocytes.

Question 6

what are portal tracts

Answer 6

These are islands of connective tissue containing branches of the portal vein and hepatic artery, running side by side, that bring blood to the sinusoids.

They also contain bile ducts, which carry bile in the opposite direction to the blood flow.

Question 7

where is bile produced in

Answer 7

produced from the hepatocytes and secreted into a network of minute bile canaliculi

Question 8

what is good about sinusoids

Answer 8

• as blood passes through sinusoids it is in intimate contact with the hepatocytes so it can exchange nutrients and metabolic products

Question 9

what is hepatic acinus

Answer 9

• it is now through that the blood flow and function of the liver are more accurately defined by the unit structure known as the hepatic acinus

Question 10

describe the hepatic lobule concept

Answer 10

• the lobule is roughly hexagonal in shape
• centred on a terminal hepatic venue
• portal tracts are positioned at the angles of the hexagon
• blood from the portal vein and hepatic artery in the portal tract flow to the central vein

Question 11

describe the hepatic acinus concept

Answer 11

• more accurate functionally then the hepatic lobule concept
• more difficult to define histologically
• berry shaped unit of liver parenchyma centred on a portal tract
• lies between two or more terminal hepatic venues and the blood flows from the portal tracts through the sinusoids to the venues

Question 12

what are the zones of the acinus

Answer 12

• divided into 3 zones
  zone 1
  zone 2
  zone 3

Question 13

describe the three zones of the acinus

Answer 13

zone 1
- most central and closest to the terminal distributing branches of the portal venue and hepatic arteriole
- receives oxygen, hormones, and nutrients from the bloodstream and is the site of the most glycogen and plasma protein synthesis
zone 2
- receives slightly less oxygenated blood
zone 3
is furthest away, receiving the least amount of oxygenated blood
- first to show ischemic necrosis and fat accumulation if metabolism is altered and the site of most drug detoxification

Question 14

what zone in the hepatic acinus is susceptible to ischaemic injury

Answer 14

zone 3 as it receives the least amount of oxygenated blood

Question 15

describe the grouping of hepatic acinus

Answer 15

• Simple acini are grouped into complex acini and they are grouped into acinar agglomerates.

Question 16

why is the connective tissue (storm) of the liver important

Answer 16

• maintains the ordered architecture of the liver and the close relationship between the hepatocytes, vasculature and the bile ducts

Question 17

what happens in cirrhosis

Answer 17

• the normal architecture is disrupted by excess fibrocollagenous tissue resulting in impaired liver function

Question 18

what are the 3 distinctive ways in which the liver deals with damage

Answer 18

Necrosis of hepatocytes
Fibrosis
Regeneration.

Question 19

what is the region called in which the larger vascular and billiard components travel

Answer 19

Portal tract

Question 20

name three major components that are located in the portal tract

Answer 20

Hepatic artery, portal vein and bile duct

Question 21

where is the central vein

Answer 21

In the centre of the lobule

Question 22

what is found between the cords of hepatocytes

Answer 22

hepatic sinusoids

Question 23

what causes haematemesis

Answer 23

• varices have very thin fragile walls so if there is any trauma such as vomiting they can rupture and this can cause haematemsis

Question 24

How does the liver respond to injury

Answer 24

• hepatocyte degeneration and intracellular accumulations
• hepatocyte necrosis and apoptosis
• inflammation
• regeneration
• fibrosis

Question 25

what are zonal necrosis

Answer 25

- this is when cells die from toxic insult or as a result of cardiac failure or other alteration in venous drainage

Question 26

what is interface hepatitis due to

Answer 26

- due to a number of chronic conditions | - results in hepatocyte death around the portal tracts

Question 27

what is bridging necrosis

Answer 27

- this is within zone 3 of the acinus - feature of severe hepatitis - in apoptotic forms typical of acute viral hepatitis, single cell die

Question 28

what follows chronic liver disease

Answer 28

- may follow an episode of acute liver injury or develop insidiously over an extended time course

Question 29

how is the severity of liver cell damage graded

Answer 29

- extent of interface hepatitis - the degree of bridging or confluent necrosis - the frequency of interlobular apoptotic hepatocytes - the density of the inflammatory infiltrate in portal tracts

Question 30

what are the stages of severity of liver cell damage

Answer 30

- staging relates to architectural disturbance and ranges from normal architecture, fibrous enlargement of portal tracts, bridging fibrosis to cirrhosis

Question 31

the greater the disturbance to liver cells ....

Answer 31

- the greater the disturbance the less likely that it is reversible once the inflammatory activity has subsided

Question 32

what happens in primary billiard cirrhosis

Answer 32

- this is when there is chronic destructive inflammatory disease centres on the bile ducts

Question 33

in primary billiary cirrhosis what do the larger bile duct show

Answer 33

- they show early change including inflammatory infiltration of their walls and surrounding tissues by lymphocytes, macrophages, plasma cells and occasional eosinophils - characterstically there is formation of granulomas near damaged bile ducts

Question 34

what is a cirrhosis

Answer 34

- not a disease itself but an end result of chronic liver injury caused by a variety of different diseases

Question 35

what are the three complications of cirrhosis

Answer 35

- liver failure - portal hypertension - hepatocellular carcinoma

Question 36

what are Stellate cells

Answer 36

- normal connective tissue cells, much like fibroblasts, responsible for the production fo the reticular tissue that supports the sinusoidal capillaries and hepatocytes in the "space of disse"

Question 37

what do stellate cells do

Answer 37

- help produce extracellular matrix - storage of vitamin A - act as capillary pericytes regulating interlobular blood flow and aid hepatic regeneration

Question 38

what does hepatic fibrosis do to stellate cells

Answer 38

- the main mechanism of hepatic fibrosis involves the activation of these cells to induce their proliferation and differentiation into highly fibrogenic "myofibroblast cells"

Question 39

what causes stellate cells to become active

Answer 39

1. factors released during chronic inflammation from Kupffer cells and lymphocytes 2. cytokines and chemokine from Kupffer cells, endothelial cells, ductal epithelium, and hepatocytes in response to disruption of the extracellular matrix 3. toxins acting directly on the stellate cells

Question 40

what is cirrhosis classified according to

Answer 40

morphology of regeneration nodules - based on the average size of regeneration nodules, cirrhosis can be classed as macro nodular (greater than 3mm) or micro nodular(less than 3mm) also by - aetiology - this can be often deduced from clinical, biochemical, immunological or biopsy findings

Question 41

what is the most common causes of micro nodular cirrhosis

Answer 41

- alcoholic liver disease

Question 42

what causes complication of macro nodular cirrhosis

Answer 42

macro nodular cirrhosis has a greater risk of complication by hepatic cell carcinoma

Question 43

what are the causes of cirrhosis

Answer 43

- viral hepatitis - alcohol haemochromatosis - autoimmune liver disease - recurrent biliary obstruction - Wilsons disease

Question 44

what is used to obtain liver

Answer 44

- needle biopsy | - this is used to obtain liver tissue for histopathological analysis during diagnosis and to monitor the disease state

Question 45

what is the mechanism of jaundice in hepatobillary diseases

Answer 45

failure of mechanism to excrete bile

Question 46

what is the mechanism of bleeding in hepatobillary diseases

Answer 46

failure of hepatic synthesis of clotting factors

Question 47

what is the mechanism of oedema in hepatobillary diseases

Answer 47

failure of hepatic synthesis of albumin resulting in decreased plasma oncotic pressure

Question 48

what is the mechanism of ascites in hepatobillary diseases

Answer 48

low serum in albumin and portal hypertension

Question 49

what is the mechanism of gynaecomastia in hepatobillary diseases

Answer 49

failure to detoxify endogenous oestrogen's

Question 50

what is the mechanism of encephalopathy in hepatobillary diseases

Answer 50

failure to detoxify ammonia and break down amino acid products

Question 51

what is the mechanism of haematonesis in hepatobillary diseases

Answer 51

bleeding from oesophageal varicose and rectum varicoses owing to portal hypertension

Question 52

most malignant neoplasms in the liver are metastases...

Answer 52

form a primary tumour in another organ

Question 53

what are aetiological factors associated with primary hepatocellular carcinoma

Answer 53

- HBV, HBC, aflatoxins, and cirrhosis

Question 54

what are aflatoxins

Answer 54

- these are carcinogenic mycotoxins which are found in food stored in humid conditions

Question 55

what type of growth is consistent with heptacellular carcinoma

Answer 55

- dysplastic hepatocyte | growth

Question 56

what is the region called in which the large vascular and biliary components travel

Answer 56

portal tract

Question 57

name the three major components that are located in the portal tract

Answer 57

Hepatic artery 􏰀 Portal vein Bile duct

Question 58

where is the central vein

Answer 58

- located in the centre of the lobule

Question 59

what type of collagen is stained black

Answer 59

collagen type III this is also known as reticulin

Question 60

what is found between the cords of hepatocytes

Answer 60

hepatic sinusoids

Question 61

In which direction does the blood flow in the liver

Answer 61

blood flows from the portal tract into the sinusoids

Question 62

in which direct does bile flow int he liver

Answer 62

flows from the hepatocytes in the bile duct towards the duodenum

Question 63

what do you get haematomesis

Answer 63

- vascular dynamics become distorted - this leads to hypertension - results in gastro-oesophageal varies, ascites and other vascular disturbances - varices tend to rupture due to their thin wall - results in haematemesis