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Alimentary system > Liver > Flashcards

Liver Flashcards

1
Q

Which quadrant is the liver found?

A

Upper right

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2
Q

How many main lobes are there?

A

2 - right and left

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3
Q

What are the names of the other two lobes?

A

caudate and quadrate

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4
Q

Name some ligaments in the liver

A
  • coronary ligament
  • ligamentum teres
  • left triangular ligament
  • falciform ligament (seperates left and right lobe)
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5
Q

Name veins and arteries of the liver

A

left hepatic vein
hepatic portal vein
hepatic artery proper

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6
Q

Where is the gallbladder found?

A

junction of segment 4 and 5

near the quadrate lobe

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7
Q

The Couinaud Classification

A
  • Features the liver as 8 functionally independent segments
    Each segment has an:
  • Artery (centrally)
  • Hepatic vein (peripherally)
  • Bile duct (centrally)
    e.g. caudate lobe
  • Each segment can therefore be cut out without damaging those remaining
  • The sections are labelled clockwise (from the centre)

Right = 1,2,3,4. Left = 5,6,7,8

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8
Q

Blood supply to the liver

A
  • The liver takes 25% of the resting cardiac output.
It has a dual blood supply:
 - 20% arterial blood from 
 hepatic artery for 
 oxygenation
 - 80% venous blood which 
 drains from gut through the 
 hepatic portal vein (nutrient 
 filled blood from gut)
  • All blood from the liver the drains into the inferior vena cava via the hepatic vein
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9
Q

What are the two main categories the micronanatomy structures can be divided into?

A

Morphological units – lobules and portal tracts/triads

Functional units – acinis, blood flow and bile flow

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10
Q

Lobules

A
  • Hexagonal
  • Divided into three parts (concentric centrilobular, midzonal and periportal)
  • Have portal triads (hepatic portal vein, hepatic artery, bile duct)
  • Blood flows towards the central canal (and bile the opposite way)
  • Periportal hepatocytes are near the portal triad
  • Periportal hepatocytes are predisposed to viral hepatitis
  • Centrilobular hepatocytes are near the central canal (blood out of liver)
  • Centrilobular hepatocytes are predisposed to ischaemia
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11
Q

Portal tracts/triad

A
  • Around the edges of adjoining lobules are the portal tracts
  • made of arteriole, branch of portal vein and a bile duct
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12
Q

How does blood flow through the lobule?

A
  • De-oxygenated, nutrient rich blood from the portal vein
  • Oxygenated blood from the hepatic artery
  • Flow towards central vein
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13
Q

Acinis

A
  • Defined as a unit of hepatocytes divided into zones dependant on proximity to arterial blood supply
  • elliptic or diamond shaped

Zone 1, periportal - close to portal triad (predisposed to viral hepatitis, nearest to the entering vascular supply and receives the most oxygenated blood making it least susceptible to ischaemic injury, involved in gluconeogenesis, oxidation of fatty acides and cholesterol synthesis)

Zone 2, transition zone – close to central canal (medium risk of ischaemia/toxins)

Zone 3, Pericentral - most susceptible to ischaemic injury, low toxin risk and is involved in glycolysis, lipogenesis and P450 based drug detoxification

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14
Q

Flow of bile

A

Bile is produced by hepatocytes and flows along canaliculus to the bile duct.

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15
Q

What is the role of the liver?

A

Functions to metabolise proteins, carbohydrates, lipids and also detoxifies the blood

  • Protein synthesis and metabolism (transamination)
  • Carbohydrate metabolism
  • Glycolysis
  • Glycogenesis
  • Glycogenolysis
  • Gluconeogenesis
  • Lipid metabolism
  • Bile acid (+ sodium) production.
  • Detoxification – at the SER and using lysosomes.
  • Metabolise, modify/detoxify exogenous compounds.
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16
Q

What are the cell types in the liver?

A
  • Hepatocytes
  • Endothelial cells
    (lining blood vessels and sinusoidal vessels which are fenestrated and allow large molecules to move to and from hepatocytes)
  • Cholangiocytes (bile duct epithelial cells, lining biliary structures)
  • Kupffer cells
    (liver macrophages, break down RBCs, secrete cytokines to activate HSC, poliferation, contraction and fribrogenesis)
  • Hepatic stellate cells
    (Vitamin A storage cells, may be activated to a fibrogenic myofibroblastic phenotype)
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17
Q

Hepatocytes

A

Are large cells with pale and rounded nuclei

Abundant

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18
Q

Kupffer and stellate cells

A

Flattened, dense cell nuclei that appear to be in the sinusoids are Kupffer cells (macrophages) or hepatic stellate cells (in space between endothelial cells and hepatocytes, can be activated when needed)

19
Q

Histology of hepatocytes

A

Histologically, hepatocytes feature in cords or
sheets that radiate from a central vein (which they
drain into).

20
Q

What do the nuclei look like for stained endothelial cells, kupffer cells and hepatocytes?

A

Endothelial cells – nuclei red and flat

Kupffer cells – blue cytoplasm, red nuclei

Hepatocytes – nuclei red and round

21
Q

What can alpha keto glutarate, pyruvate and oxoloacetate be made into (amino acids)?

A

a keto glutarate - glutamate, proline, arginine

oxoloacetate - aspartate, methionine, lysine

pyruvate - alanine, valine, leucine

22
Q

What is the function of bile?

A
  • Emulsification and absorption of fat: to increase surface area for lipase activity
  • Cholesterol homeostasis: excreting excess as needed
  • Toxin excretion: endogenous (e.g. bilirubin) and exogenous (e.g. drugs)
23
Q

Synthesis of fatty acids

A

Liver can convert amino acids and glucose into fate for storage

  1. The first step in formation of acetoacetate in the liver is the enzymatic condensation of two molecules of acetyl-CoA, catalyzed by thiolase
  2. Acetoacetyl-CoA then condenses with acetyl-CoA to form HMG-CoA which is cleaved to free acetoacetate and acetyl-CoA.
24
Q

Utilisation of glucose

A

Glucose can be directly converted to glycerol or via the TCA cycle and be converted to acetyl CoA via pyruvate
Acetyl CoA can be converted to cholesterol (via HMG CoA reductase) or can also be converted to fatty acids (via the intermediate malonyl CoA).

25
Q

What is a lipoprotein?

A

Triacyl glycerols, apoproteins, phospholipids and cholesterol

26
Q

Utilisation of amino acids

A
  • Glutamate, aspartate, alanine and glutamine are present in cells at much higher concentrations than the other 16.
  • All four have major metabolic functions in addition to their roles in proteins
  • Glutamate is special because it is chemically related to alpha keto glutatarate
  • Glutamate can be reversibly converted into oxoglutarate by transaminases or by glutamate dehydrogenase
  • In addition, glutamate can be reversibly converted into glutamine, an important nitrogen carrier, and the most common free amino acid in human blood plasma
  • Alanine is the principal amino acid released from muscle tissue during starvation
  • It is an important substrate for hepatic gluconeogenesis, and alanine transamination is required for the proper maintenance of fasting blood glucose concentrations
27
Q

Alanine transamination with alpha ketrohlutarate

A

alanine+alpha ketogultarate = pyruvate + glutamate

28
Q

What does glutamate metabolism produce?

A

NH3 - toxic so liver converts it to water soluble urea

29
Q

Liporoteins, their roles and bile

A
  • The liver produces two lipoproteins: VLDL and HDL.
  • VLDL has a high triacylglycerol component and it’s major role is to deliver fatty acids to body tissues (lipoprotein lipase cleaves the fatty acids from triglycerides)
  • HDL are often referred to have high protein content but low fat content. Their role is to mop up excess cholesterol in the circulation and return to the liver
  • Once VLDL have delivered fatty acids to tissues, they are converted to LDL which are very high in cholesterol.
  • The LDL deliver cholesterol to tissues which then use the cholesterol to make hormones and to maintain cell membrane integrity
  • Any excess cholesterol is returned to the liver and excreted in bile.
30
Q

Liver storage

A
  • Storage of fat soluble vitamins (A,D,E,K)
  • Stores sufficient for 6-12 months
  • Stored Vit B12
  • Stored copper
  • Vit K store is small: Vit K is essential in blood clotting
  • Storage of iron as ferritin: available for erythropoeisis
31
Q

Liver - detoxification

A

P450 enzymes

Phase 1 - more hyrdrophilic

Phase 2 - attach water
soluble side chain to make
less reactive

32
Q

What is a hepatic lobule?

A

A structural unit of the liver with rows of hepatocytes with a sinusoid facing side and a bile caniculi facing side.

33
Q

Biliary tree

A
  • The biliary tree describes the anatomical structures responsible for the transit and storage of bile
  • Starts in millions of bile canaliculi adjacent to the hepatocytes (bile producing cells)
    Canaliculi -> small ductules
    -> small bile ducts -> larger bile ducts for each liver segment -> right and left hepatic ducts -> common hepatic duct
  • Connected to this duct is the cystic duct, which connects the gall bladder to the biliary tree

Common hepatic duct and the cystic duct -> common bile duct, which extends towards the duodenum

At its distal end the pancreatic duct joins and the vessel is then called the ampulla of Vater, which opens up into the medial wall of the duodenum at the duodenal papilla

34
Q

What is a hepatic acinus?

A

A functional unit of the liver with two adjacent areas one sixth of lobules that share two portal triads and extend to the central vein.

35
Q

What do hepatocytes contain (organelles)?

A
  • nucleus
  • lysozymes
  • glyocogen
  • peroxisomes (detoxification, waste management and cholesterol/bile synthesis)
  • cytoplasmic enzymes
  • smooth ER
  • mitochondria (lots)
  • rough ER
  • Golgi
36
Q

What does bile contain?

A
  • cholesterol (in high/low amounts) for homeostasis of cholesterol
  • bile salts to solubilise fatss
  • bilirubin and drug metabolites (for excretion in faeces of both endogenous and exogenous)
    lots of water
37
Q

Which cells secrete and modify bile?

A

hepatocytes (primary secretion)

cholagniocytes (epithelial cells of bile duct) - secondary modification, alter pH, water movement, reabsorption of sugars and acids, secretion of HC03- and Cl-

38
Q

Primary bile acids and secondary bile acids

A

Two primary bile acids are made in the liver - cholic acid and chenodeoxycholic acid

Two secondary bile acids are made from primary ones by gut bacteria - deoxycholic (from cholic acid) acid and lithocholic acid

39
Q

What does the gallbladder do?

A
  • stores bile (50ml)
  • acidifies bile by absorbing bicarbonate
  • concentrates bile by reabsorbing ions and creating an osmotic gradient
40
Q

When is bile released?

A

constantly synthesised and stored in gallbladder

CCK stimulates gallbladder contraction for a large amount

41
Q

Why is bile yellow/green?

A

contains bilirubin and biliverdin

42
Q

How much bile is made daily?

A

500ml

43
Q

What is enterohepatic circulation?

A
  • Means that substances can cycle between the gut and liver by continuous reabsorption in the gut, carriage in portal blood to liver, and hepatocyte secretion into bile canaliculi, to be secreted (in bile) via the common bile duct
  • Bile can be recycled so useful
  • Liver processes some drugs by excreting them via bile and eventually the faeces. But they may get reabsorbed in the small intestine and re-enter the portal circulation cyclically
44
Q

What are sinuosoids?

A

Where blood flows from one side of lobule to the other

Alimentary system (14 decks)

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