Anatomy & Function of the Liver Flashcards
1
Q
Where is the liver located ?
A
upper right-hand portion of the abdominal cavity
- beneath the diaphragm
- ontop of the stomach
2
Q
What is the overall structure of the liver?
A
- 2 lobes
- each lobe is made up of 8 segments that consist of 1000 lobules
- lobules are connected to small ducts connected to larger ducts to form the common hepatic duct
3
Q
What is the function of the common hepatic duct ?
A
- transports bile made by the liver cells to the gallbladder & duodenum
4
Q
Describe why the liver is a vascular organ ?
A
- hepatic artery = supplies 02 rich blood from heart to liver
- portal vein = supplies nutrient rich blood from digestive tract
5
Q
What is present in every liver lobule ?
A
- serval portal triads
6
Q
What 5 structures make up a portal triad ?
A
- proper hepatic artery
- hepatic portal vein
- 1/2 small bile ducts
- lymphatic vessels
- branch of the vagus nerve
7
Q
Describe the proper hepatic artery
A
- an arteriole branch of the hepatic artery that supplies oxygen
8
Q
Describe the hepatic portal vein
A
- a venue branch of the portal vein, with blood rich in nutrients but low in oxygen
9
Q
What are the functions of the liver ?
A
- manufactures bile
- controlling levels of fats, amino acids & glucose
- cholesterol synthesis
- clears blood of infections
- stores iron & vitamins
9
Q
Where is bile produced ?
A
the liver
10
Q
Where is bile stored ?
A
in the gallbladder
11
Q
What is the function of bile ?
A
- required for digestion & fat absorption
- endogenous synthesis of bile salts
- absorption of fat soluble vitamins
- major route for loss of cholesterol
12
Q
What is the composition of bile ?
A
- bile salts
- phospholipids
- cholesterol
- bilirubin
13
Q
What synthesises bile salts ?
A
- hepatocytes
- bile pigments are picked up from blood sinusoids
14
Q
What is the daily secretion of bile ?
A
500 mls
15
Q
What are bile acids formed from ?
A
- cholesterol in the liver
- conjugated with glycine & taurine
16
Q
What is the process of metabolism of bile salts in the liver ?
A
- biosynthesis of bile acids from cholesterol
- conjugation with amino acids
- conc. in gallbladder by removal of water
- intestinal bacteria in colon produce enzyme that can attack/alter bile salts
- most bile acids are reabsorbed from intestine, transported to liver and reverted to bile
17
Q
Define enterohepatic circulation
A
the process by which substances are metabolised by the liver, secreted into liver and then reabsorbed into the body
18
Q
Describe the metabolism of bilirubin
A
- 120 days RBCs are phagocytised & haemoglobin is released
- haemoglobin is broken down into Haem, globin & iron
19
Q
What happens to haem in the blood ?
A
its converted to bilirubin
20
Q
What happens to globin in the blood ?
A
it’s broken down into amino acids & recycled
21
Q
What happens to iron in the blood ?
A
- bound by transferrin & returned to iron stored in the liver or bone marrow
22
Q
Where is bilirubin degraded ?
A
-intestines
- intestinal bacteria degrade conjugated bilirubin to form urobilinogen
22
Q
What happens to bilirubin at the liver ?
A
- unconjugated bilirubin flows into sinusoidal tissue, albumin releases it
- ligandin binds to unconjugated bilirubin presents it to glucuronic acid
- in the liver it becomes conjugated by UDP-glucuronyl transferase
23
What happens to 80% of urobilinogen ?
- its oxidised to stercobilin & excreted in faeces, giving stool brown colour
24
What happens to 20% of urobilinogen ?
- absorbed by extra hepatic circulation to be recycled through liver & re-excreted
- enters systemic circulation to be filtered by kidneys & excreted via urine
25
What are the main 2 functions of the liver in iron homeostasis ?
1. major site of iron storage, regulates iron traffic into/around body via production of peptide hepcidin
2. site of synthesis of major proteins in iron metabolism
26
What does hepcidin do?
- binds to ferroportin, inhibiting iron absorption/efflux
27
Where are coagulation factors mainly synthesised ?
- in the liver
28
What is the function of Liver Function Tests (LFTs) ?
1. Detect presence of disease
2. distinguish different types of liver disorders
3. extent of liver damage
4. follow response to treatment
29
How is the sample for an LFT taken?
- test is done on serum of patient
- random sample can be taken
- serum is stable for 3 days a 1-6 degrees
30
What are some precautions that should be taken with an LFT ?
- Avoid haemolytic
- for bilirubin fasting sample is preferred
- protect serum/plasma from light
31
What are the 2 subdivisions of LFTs?
1. true tests of liver function
2. tests indication liver injury or biliary tract disease
32
How are different LFTs classified ?
- based on major functions
1. excretion
2. serum enzymes
3. synthetic function
33
Describe an Excretion LFT
- serum bilirubin
- true test of liver function as it reflects livers ability to take up, process & secrete bilirubin into the bile
- conjugated = direct - excreted by kidney
- unconjugated = indirect - bound to albumin
34
What enzymes reflect damage to hepatocytes ?
- aspartate aminotransferase (AST)
- alanine aminotransferase (ALT)
^
These are sensitive indicators of liver cell injury
35
Where are aspartate aminotransferase found ?
liver, cardiac muscle, kidneys, brain & erythrocytes
36
Describe Aminotransferase
- normal = 10-40 U/L
- <300 U/L nonspecific may be found in any liver disorder
- >1000 U/L = extensive hepatocellular injury = viral hepatitis, ischaemic liver injury or acute heart failure
37
Describe the pattern of aminotransferase in different diseases ?
- acute hepatocellular disorders = ALT > AST
- chronic viral hepatitis = ALT > AST
- Cirrhosis = AST > ALT
38
What does enzymes reflect cholestasis ?
- alkaline phosphatase
- gamma glutamyl transpeptidase
39
Describe Alkaline Phosphatase
- not specific for cholestasis
- < 3 fold in any type of liver disease
- > 4 fold in cholestatic liver disorders & infiltrative disease such as cancer
40
What are some examples of why non pathological elevation of alkaline phosphatase can occur ?
- Age over 60
- rapid bone growth
- late pregnancy
41
What can hypoalbuminaemia reflect ?
- common in chronic liver disorders = cirrhosis
- reflects severe liver damage & decreased albumin synthesis
- not specific for liver disease
42
Describe LFT measuring Prothrombin time (PT)
- prothrombin = plasma protein converted into thrombin during blood clotting
- formed in liver from inactive preprothrombin in the presence of Vit K
- Used to assess activity of extrinsic blood clotting pathway
43
What is the PT test expressed as ?
International Normalised Ration I(NR)
- Based on ratio of patients prothrombin time & normal mean prothrombin time
44
Which lobe of the liver is the largest ?
- the right lobe
45
Which cells in the liver are responsible for phagocytosis ?
- Kupffer cells
46
Which vitamin is stored in significant amounts in the liver ?
- Vitamin A
47
Which substances does the liver detoxify ?
- drugs, alcohol & ammonia
