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Phase 2 1. Gastroenterology > Structure & function of liver > Flashcards

Structure & function of liver Flashcards

1
Q

Where is the liver located?

A

Found in theupper right quadrantof the abdomen

Located in the right hypochondriumandepigastrcarea,
extending into the left hypochondrium

● Mostly located underneath the rib cage as it is vulnerable to injury

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2
Q

List the functions of the liver

A
  • processing
  • amino acid, carbohydrate, lipid metabolism
  • plasma protein and enzyme synthesis (clotting factor production)
  • bile production
  • detoxification
  • storage pf proteins, glycogen, vitamins and metals
  • immune functions
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3
Q

What are the 4 main aspects of the liver?

A
  • vasculature
  • parenchymal liver cells
  • biliary system
  • connective tissue matrix
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4
Q

What are the 4 anatomical lobes of the liver?

A

Right lobeis the largest and theleft lobeis a flattened smaller one.
▪ Separated along the attachment of thefalciform ligament
o Caudate and aquadrate lobeare part of the anatomical right lobe

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5
Q

Describe the portal circulation?

A

Blood entering the liver through the portal vein has already been
through the gut capillary bed
o Nutrient rich, low pressure blood
o Any increase in resistance in the liver makes it difficult for
blood to flow through, as it is flowing at a low pressure
● Once the vessels enter the liver via the porta hepatis, they enter
the parenchyma (called connecting sinusoids) and then eventually
drain to the hepatic vein
● Portal vein has a wide calibre and thin walls

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6
Q

List the vasculature of the liver

A
  • hepatic artery proper
  • hepatic portal vein
  • connecting sinusoids
  • hepatic vein
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7
Q

Where does the hepatic artery proper stem from?

A

Branches from thecoeliac trunk

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8
Q

Describe the Hepatic portal vein

A

Supplies the liver withdeoxygenated blood, carrying nutrients absorbed from the small
intestine.

This is the dominant blood supply to the liver parenchyma, and allows the liver to perform its
gut-related functions, such as detoxification

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9
Q

Describe the connecting sinusoids

A

The liver tissue is not vascularised with a capillary network as with most other organs, but consists of blood filled sinusoids surrounding the hepatic cells

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10
Q

Describe the Hepatic vein

A

leaves the liver on the posterior side
o NB: this is not the same as the portal vein
o Venous drainage of the liver is achieved through three hepatic veins, which drain into theinferior
vena cava

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11
Q

What are the portal tracts?

A

Hepatic artery and portal vein lie in portal tracts along with bile ducts

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12
Q

What is the pota hepatis?

A 
– “gateway to the liver”
o 3 main structures enter/leave the liver at this point:
▪ hepatic artery
▪ hepatic portal vein
▪ bile duct
o These are known as the portal triad
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13
Q

Describe the microscopic structure of the liver

A
  • arranged in lobules comprised of rows of hepatocytes radiating out from a central point
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14
Q

Describe the hepatic lobules

A

Each lobule ishexagonal-shaped, and is drained by a venule in its centre, called acentral vein.
o Blood flows out of the sinusoids into the central vein, removing detoxified substances and
metabolic end products.
o The central vein ultimately reunites with the
hepatic vein transporting these substances out of
the liver.

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15
Q

How does bile drain from the lobules?

A

Bile produced by the hepatocytes drains into tiny canals called bile canaliculi
o These drain into bile ducts located around the
lobule perimeter

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16
Q

Describe the arrangement of hepatocytes?

A

Lie in plates and cords
o Each hepatocyte is a plate, joins to neighbouring
hepatocytes

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17
Q

What makes sinusoids different from capillaries?

A

more leaky than capillaries. In the liver, this is achieved by:
● Fenestrations (holes)
● Less well-developed, thinner basement membrane
● This design specifically enhances exchange

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18
Q

Name the parenchymal liver cells

A
  • hepatiocytes
  • endothelial cells
  • kupffer cells (macrophages)
  • perisinusoidal (fat-storing) cells
  • liver associated lymphocytes
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19
Q

What connective tissue can be found in the liver?

A
  • liver capsule
  • portal tracts
  • parenchymal reticulin
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20
Q

Describe the bile canaculi

A

o Intercellular adaptation
o Run between hepatocyte plates and cords but run in the opposite direction of blood flow
o Drain into portal tracts (portal triads)
o Lots of active transport (high ATPase activity)

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21
Q

What do the bile canaculi lead to?

A

=> bile ductules => bile ducts

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22
Q

How can vascular and biliary systems be affected by fibrosis?

A

some of the incoming and outgoing blood vessels join up
● This means that shunts can form within the liver, which has bad consequences
● Some of the incoming blood starts to bypass the liver as a result
● Fibrosis causes reduced function as there is reduced capacity for work
● Vascular resistance increases, causing portal hypertension

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23
Q

where is bile produced?

A

liver

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24
Q

Where does bile get stored?

A

gallbladdrr

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25
Q

What is the function of bile?

A

aids in digestion of fat in duodenum

26
Q

What does bile help absorb?

A

fat-soluble vitamins

27
Q

Name the fat soluble vitamins

A
  • A
  • D
  • E
  • K
28
Q

What does bile help excrete?

A

bilirubin

29
Q

what is bilirubin derived from?

A

fromhemoglobinbyglucuronidation

30
Q

What changes occur to bile in the gallbladder?

A

concentrated to about 5 times—and sometimes as high as 18

times—the strength of the original secretion.

31
Q

What hormones control the secretion of bile into the duodenum?

A

cholecystokinin,secretin,gastrin, andsomatostatinand thevagus nerve

32
Q

Describe the contents of bile

A
  • bile acids & salts
  • phospholipids
  • cholesterol
  • pigments
  • water
  • electrolyte chemical
  • taurocholic acid
33
Q

What is taurocholic acid?

A

chemical is released into the bile by the liver. Plays a role in digestion in the small
intestine (involved in the emulsification of fats)

34
Q

What are bile salts and acids

A

synthesised from cholesterol or extracted from bloodstream

35
Q

What is the function of bile acids or salts?

A

act as detergents to emulsify fat and reduce surface tension on fat droplets to prepare them for action of pancreatic and intestinal lipases

36
Q

Where do bile salts come from?

A

only 10% of the daily requirement for bile salts. The remainder thus has to be
reabsorbed and re-circulated.

37
Q

Describe the chemical nature of bile salts

A

The salts are large, negatively charged ions that are not readily absorbed by the upper region of the small
intestine; consequently, they remain in the small intestine until most of the fat is digested.

38
Q

How are bile salts recycled?

A

the salts and acids are absorbed and passed back into the bloodstream until
they are once again extracted by the liver; this cycle, from the liver to the small intestine and blood and then back to the liver, is calledenterohepatic circulation

Ileum is the main site of bile salt reabsorption

39
Q

What does bilirubin levels tell you about the liver?

A

increase in cholestasis

40
Q

What does alk phos levels tell you about the liver?

A

increase in cholestasis

41
Q

What is alk phos?

A

alkaline phosphatase - enzyme in the cells lining the biliary ducts of the liver

42
Q

What is GGT?

A

gamma glutamyl transpeptidase

43
Q

What does GGT levels tell you about the liver?

A

Increase in cholestasis or enzyme induction

44
Q

What does AST/ALT levels tell you about the liver?

A

increase in hepatocyte damage

45
Q

What is ALT?

A

Alanine transaminase

46
Q

What is AST?

A

Aspartate transaminase

47
Q

What is the significance of raise AST?

A

raised in acute liver damage, but is also present in red blood cells, and
cardiac and skeletal muscle, so is not specific to the liver.

48
Q

What is the best way of differentiating between ccauses of liver damage?

A

using AST/ALT ratio

49
Q

Describe the pattern of LFTs in pre-hepatic jaundice

A
  • increased total bili
  • normal conj. bili
  • increased unconj. bili
  • normal or raised urobilinogen
  • normal urine colour
  • normal stool colour
  • normal alk phos
  • normal ALT and AST
50
Q

Describe the pattern of LFTs in hepatic jaundice

A
  • increased total bili
  • increased conj. bili
  • increased unconj. bili
  • increased urobilinogen
  • dark urine colour
  • normal stool colour
  • increased alk phos
  • v. highALT and AST
51
Q

Describe the pattern of LFTs in post-hepatic jaundice

A
  • v. high total bili
  • v. high conj. bili
  • normal unconj. bili
  • low urobilinogen
  • dark urine colour
  • pale stool colour
  • v. high alk phos
  • increased ALT and AST
52
Q

What is cirrhosis?

A

Diffuse (throughout the liver) process with fibrosis and nodule formation

53
Q

How does cirrhosis occur?

A

chronic inflammation (broadly “hepatitis”) over many years
o Persistence of injury-causing agent
o Causes (fibrous) scarring (fibrosis) and hepatocyte regeneration
▪ regeneration would be a good thing if the underlying architecture was intact, but the
disturbed architecture leads to formation of nodules instead
▪ Nodules squeeze on surroundings (vasculature and bile ducts), causing reduced blood
flow

54
Q

What are the main causes of cirrhosis?

A 
● Alcohol or alcohol-like 60-70%
● Hepatitis incl. viral B, C (+D) 10% or more
● Biliary disease 5%
● Unknown 10-15%
● Haemochromatosis 5%
55
Q

What are the causes of hepatitis?

A 
● Alcohol
● Metabolic disease
● Viral infections
● Auto-immune hepatitis
● Many others
56
Q

What are the features of fatty liver cirrhosis

A

● small nodules

● yellowy/orange colour

57
Q

What are the complications of liver cirrhosis?

A
  • portal hypertension
  • liver failure
  • hepatocellyular (liver) cancer
58
Q

Describe the cause of portal hypertension

A

Cirrhosis increases resistance to blood flow through liver thus increasing pressure in the portal
circulation.

59
Q

What are the consequences of portal hypertension?

A

▪ Portal-systemic shunts and varices (gastro-oesophageal junction, around rectum and
umbilicus)
>Veins may rupture to give massive hematemesis and precipitate hepatic failure
and encephalopathy
▪ Ascites
▪ Splenomegaly

60
Q

What proteins are imapired due to liver damage?

A 
● Albumin
● Transport proteins
● Coagulation and fibrinolysis proteins e.g. Factors II, V, VII-XIII
● Complement
● Protease inhibitors
61
Q

What are the effects of liver failure

A

● Jaundice
● Coagulation disorders
● Altered intermediary metabolism e.g. impaired synthesis of urea and glycogen
● Altered xenobiotic metabolism e.g. drugs
● Immune, circulatory and endocrine disturbances
● Reduced albumin and other transport proteins (impaired production of secretory proteins)

Phase 2 1. Gastroenterology (20 decks)

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