Liver

Question 1

Describe the gross anatomy of the liver.

Answer 1

1. 4 lobes: left, quadrate, right and caudate; in dog/cat left and right split into medial and lateral; caudate love has caudate and papillary processes
2. Gall bladder (absent in horses and rats)

Question 2

Why is the liver lobated?

Answer 2

Allows movement of organ due to diaphragm.

Question 3

What are the functional units of the liver?

Answer 3

Hepatic acinus

Question 4

What cells make up the liver’s structure?

Answer 4

Hepatocytes and Kupffer cells

Question 5

What are hepatocytes?

Answer 5

• Chief functional cells of liver
• Absorb ,molecules from ‘Space of Disse
• Bile Canaliculus is dilated intercellular space between cells

Question 6

What is the sphincter of Oddi?

Answer 6

• A muscular valve controlling the flow of bile and pancreatic juice into the duodenum.
• Loacted at the junction of common bile duct and pancreatic duct.

Question 7

What are the two sources of blood to the liver?

Answer 7

1. Hepatic portal vein
2. Hepatic artery

Question 8

What is a sinusoid in the liver?

Answer 8

• A specialized, low-pressure blood vessel in the liver that allows the mixing of oxygen-rich blood from the hepatic artery and nutrient-rich blood from the portal vein.
• Lined with fenestrated endothelial cells.
• Surrounded by layers of hepatocytes.
• Macrophages (Kupffer cells) patrol sinusoids.

Question 9

Describe the transport of blood after the sinusoids.

Answer 9

1. Blood from sinusoids empty into central veins
2. Central veins coalesce into hepatic veins
3. Hepatic veins empty into caudal vena cava

Question 10

Describe the structure of a hepatic lobule.

Answer 10

1. Hexagonal in shape
2. Lobules made of plates of hepatocytes
3. Hepatocytes radiate outwards from a central vein
4. Between the lobules are portal tracts (triads): bile duct, hepatic artery, hepatic portal vein.

Question 11

What are Kupffer cells, and what do they do?

Answer 11

Liver macrophages that phagocytose pathogens and old erythrocytes.

Question 12

List some liver functions.

Answer 12

• Synthesis of cholesterol and bile acids.
• Synthesis of plasma proteins.
• Breakdown of RBC.
• Carb, lipid and amino acid metabolism.
• Removal of bacterial
• Production of clotting factors
• Storage of glycogen, iron, copper and vitamins.
• Detoxification of Body Wastes, Xenobiotics and Drugs.

Question 13

What are the two phases of liver detoxification?

Answer 13

Phase I: Functionalization reactions (oxidation, reduction, hydrolysis).
Phase II: Conjugation reactions to make substances water-soluble.

Question 14

What enzyme system is central to Phase I detoxification?

Answer 14

The cytochrome P450 enzyme family.

Question 15

Where are detoxified substances excreted?

Answer 15

Into bile (via the bile canaliculi) or urine (via the bloodstream and kidneys).

Question 16

How does the liver detoxify ammonia?

Answer 16

By converting it into urea through the urea cycle, which is then excreted in urine.

Question 17

Where are aged or damaged RBCs primarily degraded?

Answer 17

In the liver and spleen by macrophages (including Kupffer cells in the liver).

Question 18

How is heme processed during RBC degradation?

Answer 18

Into bile pigments -
1. Heme is converted into biliverdin by heme oxygenase.
2. Biliverdin is reduced to bilirubin by biliverdin reductase.

Question 19

What occurs to bilirubin in the liver?

Answer 19

It is conjugated with glucuronic acid to form conjugated bilirubin, making it water-soluble.

Question 20

How is conjugated bilirubin excreted?

Answer 20

It is secreted into bile and released into the small intestine.

Question 21

What happens to bilirubin in the intestine?

Answer 21

• It is converted into urobilinogen by intestinal bacteria.
• Urobilinogen can be reabsorbed, excreted in urine as urobilin, or oxidized to stercobilin and excreted in feces.

Question 22

What are the main functions of bile?

Answer 22

1. Emulsification of dietary fats for digestion and absorption.
2. Excretion of waste products like bilirubin and excess cholesterol.

Question 23

What is bile composed of?

Answer 23

Water, electrolytes, biliary proteins, bile pigments, cholesterol, phospholipids and bile acids/salts.

Question 24

Where is bile stored?

Answer 24

In the gallbladder, where it is concentrated until needed for digestion.

Question 25

How are bile acids synthesized?

Answer 25

From cholesterol in hepatocytes, involving enzymatic steps converting cholesterol into primary bile acids.

Question 26

What are the two primary bile acids and how are they made water soluble?

Answer 26

- Cholic acid - Chenodeoxycholic acid Conjugated with glycine or taurine.

Question 27

What are secondary bile acids?

Answer 27

- Following participation in lipid digestion and absorption primary bile acids move into ileum. - In terminal ileum some primary bile acids can be modified by bacteria.

Question 28

How are bile acids secreted?

Answer 28

Secreted into bile canaliculi (via active process) and flow into the bile duct, then stored in the gallbladder or released into the duodenum.

Question 29

What is enterohepatic circulation?

Answer 29

The recycling process where bile acids are reabsorbed in the ileum via active transport, returned to the liver via the portal vein, and reused for bile synthesis.

Question 30

What regulates bile secretion?

Answer 30

1. Cholecystokinin (CCK): Stimulates bile release in response to fat in the duodenum. 2. Secretin: Increases bile flow by stimulating bicarbonate secretion. 3. Neural input: Parasympathetic stimulation enhances bile secretion.

Question 31

What are common consequences of liver disease?

Answer 31

1. Jaundice (due to excess bilirubin). 2. Coagulopathies (impaired clotting factor synthesis). 3. Ascites (fluid accumulation in the abdomen). 4. Hepatic encephalopathy (due to ammonia buildup).

Question 32

What are common diagnostic markers of liver disease?

Answer 32

1. Elevated liver enzymes (ALT, AST). 2. High bilirubin levels. 3. Low albumin. 4. Prolonged clotting times. 5. High levels of bile acids in blood after meal.

Question 33

What is cholestasis?

Answer 33

A condition characterized by impaired bile flow, leading to accumulation of bile components in the blood.

Question 34

What is a porto-systemic shunt (PSS)?

Answer 34

An abnormal blood vessel that allows blood from the portal vein to bypass the liver and flow directly into systemic circulation.

Question 35

What are the two types of PSS?

Answer 35

1. Congenital PSS (present at birth). 2. Acquired PSS (secondary to chronic liver disease and portal hypertension).

Question 36

What are clinical signs of PSS?

Answer 36

1. Poor growth or failure to thrive. 2. Neurological signs (hepatic encephalopathy: seizures, head pressing, ataxia). 3. Vomiting, diarrohea, or anorexia. 4. Polyuria and polydipsia.

Question 37

Describe the route of bile production and secretion into duodenum.

Answer 37

1. Synthesised in the hepatocytes. 2. Travels from the hepatocytes via the intra-hepatic bile ducts. 3. Then to the extra-hepatic bile ducts. 4. Finally to common bile duct --> duodenum at the major duodenal papilla.

Question 38

Describe the route of bile production and secretion into gall bladder.

Answer 38

New bile travels to the gall bladder via the intra-hepatic bile ducts to the extra-hepatic bile ducts and finally the cystic duct into the gall bladder.