Hepatic System Flashcards
1
Q
What is the largest gland + largest internal organ in the body ?
A
- the liver
2
Q
How many lobes does the liver contain ?
A
- 4 lobes
- 2 Major (Left & Right) -largest
- 2 Minor (Caudate & Quadrate)
3
Q
What is the liver covered by ?
A
- a single layer of mesothelium
4
Q
Where is the gall bladder located in relation to the liver ?
A
- under the right lobe
5
Q
What is one of the primary functions of the liver ?
A
- Functions as exocrine gland – bile secretion
6
Q
What is a liver lobule composed of ?
A
– Central terminal hepatic venule
– Interconnecting plates of hepatocytes
– Peripherally arranged portal triad (hepatic artery, portal vein and bile duct )
7
Q
What are the hepatocyte zones ?
A
- centrilobular, periportal, mid zone
8
Q
What 2 vessels does liver receive its blood from ?
A
- hepatic portal vein
- hepatic artery
9
Q
What is the function of the hepatic portal vein ?
A
- blood to the liver, 75% blood supply to liver
- nutrient rich blood from digestive tract and spleen
- filters toxins from digestive tract
10
Q
What is the function of the hepatic artery ?
A
- Oxygenated blood from aorta
• 25% Blood Supply
11
Q
What are the sinusoids in the liver ?
A
- endothelium lined spaces in lobule, replacing capillaries
12
Q
What are the sinusoids partly lined with and what is their function ?
A
- lined with Kupffer cells (phagocytes)
- function is to destroy bacteria + worn-out blood cells
13
Q
What are hepatic stellate cells function + location ?
A
• Pericytes found in space of Disse (perisinusoidal space)
• Retinoid storage (in lipid droplets)
14
Q
What does damage to hepatic stellate cells lead to ?
A
- leads to transdifferentiation into proliferative fibrogenic myofibroblasts and liver fibrosis
15
Q
What percentage of hepatocyte surface area faces sinusoid ?
A
- 70% to maximise blood exchange
16
Q
What percentage of hepatocyte surface area faces bile canaliculi ?
A
- 15%
17
Q
What happens to bile canaliculi in the liver ?
A
- merge into bile ductless, running alongside portal veins
18
Q
What are the main functions of the liver ?
A
- Xenobiotic detoxification and metabolism
• Decomposition of erythrocytes and excretion of bilirubin
• Bile Production
• Cholesterol synthesis and Lipogenesis
• Carbohydrate Metabolism
19
Q
What proteins does the liver synthesise ?
A
- Albumin (major osmolar component of blood serum)
• Coagulation factors : fibrinogen, prothrombin, factors (V, VII, IX-XI), antithrombin
20
Q
What hormones does the liver produce ?
A
• Thrombopoietin (regulates platelet production by bone marrow)
• Angiotensin (raises blood pressure following renin activation)
21
Q
What does the liver store ?
A
• Glycogen
• Vitamins A, D, E, K (fat soluble), B12 (water soluble)
• Iron, Copper
22
Q
What happens when there is a decline in glucose level ?
A
- glycogenolysis = glycogen —-> glucose
- if glycogen exhausted = gluconeogenesis
23
Q
What is the Cori cycle ?
A
- lactate converted to glucose
24
Q
what is the alanine cycle ?
A
- Degradation of proteins - amino groups transferred to pyruvate
- giving rise to alanine, which is transported to the liver
- it’s carbon skeleton is converted into glucose
25
How does the liver convert glucose into fatty acids ?
- via acetyl-CoA, which is then used to form fatty acids
26
What does the liver do with fatty acids supplied from intestine ?
- receives fatty acids from lipids in chylomicrons from intestine
- converted into neutral fats and phospholipids
27
What percentage of cholesterol is produced by the liver ?
- 70%
28
What is cholesterol used for ?
- synthesis of bile acids
- cells membranes
- hormones
29
What happens to excess cholesterol ?
- converted into bile acids or excreted with the bile
30
What are bile acids ?
- steroids synthesised in the liver form cholesterol
31
What does it mean when bile acids are amphipathic ?
- have a polar and a polar side , act as detergents
32
How do bile acids form bile salts ?
- linked to amino acids
33
What components are found in bile ?
- organic = bilirubin
- inorganic = bile salts
34
Where is bile produced and how does it move within the liver ?
- produced by hepatocytes
- Bile canaliculi carry bile back to the portal triad (opposite direction to blood)
35
How does bile aid in lipid digestion ?
- bile facilitates solubilisation of lipids by forming micelles which can be absorbed by the intestines
36
What happens to erythrocytes and the end of their life span ?
- phagocytosed haemoglobin released
- blobs metabolised + amino acids recycled
- iron bound to transferrin + returned to liver
- Haem converted to bilirubin, bound to albumin
37
How is bilirubin metabolised in the liver ?
- Bilirubin **dissociates** from albumin & enters hepatocytes
• Bilirubin **conjugated** with two glucuronic acids by **UDP-glucuronyl transferase** (bilirubin diglucuronide)
• Conjugated bilirubin transported into bile canalculi and bile.
- Intestinal bacteria degrade bilirubin to **urobilinogen**
- 80% oxidised to **stercobilin** and excreted in **faeces**
• 20% enters **extrahepatic circulation** and excreted in **urine**
38
What role does the liver replay in biotransformation + metabolism ?
- acts as against gatekeeper between circulation + absorbed substances from the GI tract
- metabolizing both natural and foreign substances (e.g., drugs).
39
What is the first pass effect in metabolism ?
- after absorption from the GI tract, a significant portion of a substance may be metabolically inactivated in the liver before it reaches circulation, making dosage important.
40
What happens during phase I reactions of drug metabolism ?
- make parent compound more polar by adding or unmasking functional groups
41
What happens during phase II reactions ?
• Conjugation with endogenous substrate to increase aqueous solubility
• Conjugation with glucoronide, sulfate, acetate, amino acid etc.
42
What is an example of a phase I reactions ?
- Oxidation Reactions (Cytochrome P450’s):
- Oxygen incorporated into drug
- Oxidation causes loss of part of drug
43
What are 2 examples of substrates for Cyt P450 isozymes ?
- caffeine
- estradiol
44
What is an example of phase II reactions ?
- Glucuronidation- UDP-Glucuronosyltransferase:(-OH, -COOH, -NH2,-SH)
45
What is Hepatitis ?
- inflammation of liver
46
What is Cirrhosis ?
- formation of fibrous tissue in liver replacing dead cells
47
What is Haemochromatosis ?
- excessive iron accumulation and liver damage
48
What are Hepatic system cancers ?
- hepatocellular carcinoma
- cholangiocarcinoma
49
What is Wilson’s disease ?
- hereditary disease causing copper retention
50
What is Biliary cirrhosis ?
- disease of small bile ducts
51
What is Gilbert’s syndrome ?
- genetic disorder of bilirubin metabolism
52
What is Jaundice ?
- Yellow coloured skin, nail beds & sclera caused by deposition of bilirubin due to hyperbilirubinemia
53
What is the role of Alanine aminotransferase (ALT) is liver function tests ?
- Increased when cells of the liver are inflamed or undergo cell death
- Rises dramatically in acute liver damage, such as viral hepatitis
54
What is the significance of Aspartate aminotransferase (AST) in liver function tests?
- AST is raised in acute liver damage, but it is less specific for liver disease compared to ALT.
55
What does Alkaline Phosphatase (ALP) indicate in liver function assessment?
- Raised in biliary tract damage and inflammation, indicating issues with bile flow
56
What is the role of Gamma-Glutamyl Transferase (GGT) in liver function tests ?
- Produced by the bile duct (sensitive marker for cholestatic damage)
- Raised in alcohol toxicity
57
How is bilirubin used in liver function assessments?
- measured in plasma total and direct (conjugated) forms
- Urine may show urobilinogen and bilirubin levels, indicating liver or bile duct function.
58
What is paediatric jaundice and why does it occur?
- occurs in newborns due to low levels of bilirubin glucuronyl transferase in the liver, causing inefficient conjugation of bilirubin.
59
How does the liver function in childhood?
- liver produces insulin-like growth factor-1 (IGF-1), a hormone important for growth during this period.
60
What age-related changes occur in the liver during geriatrics?
- the liver’s oxidative capacity decreases,
- leading to reduced metabolism, longer drug exposures, and decreased toxin clearance.
