Pigments

Question 1

What is melanin?

Answer 1

A yellow-brown pigment formed by melanocytes

• Protein -tyrosine complex
• Involves tyrosinase enzyme
• Pigment is excreted out of the cell
• Melanocytes produce variable amounts of granules

Question 2

What is congenital decreased formation of melanin?

Answer 2

Albinism

Question 3

What is acquired decreased formation of melanin?

Answer 3

• Melanocyte damage
• Copper deficiency
• Vitiligo
• Hormonal imbalances

Question 4

What increases formation of melanin?

Answer 4

• UV light - increases the efficiency of the melanocytes

Question 5

What arises from increased formation of melanin?

Answer 5

• Congenital melanosis
• Moles
• Melanoma

Question 6

What results from breakdown of haemoglobin?

Answer 6

• Jaundice
• Anaemia
• Bruising
• “red water”

Question 7

What is Haemaglobin made up of?

Answer 7

• Heme
• Globin
• Iron

Question 8

What is haemolysis?

Answer 8

The lysing of RBCs

Question 9

What happens in normal recycling of RBCs?

Answer 9

• Occurs in splenic macrophages
• Extravascular haemolysis
• Hb breaks down into Heme, Iron and globin

Iron -> Haemosiderin
Heme -> bilirubin
Globin- -> AA’s

Question 10

Describe Extravascular Haemolysis…

Answer 10

Is a normal process where splenic macrophages remove old RBCs

• Can be excessive in some diseases where there is excessive phagocytosis and breakdown
  e. g. Malaria and incompatible blood transfusions

Question 11

Describe Intravascular Haemolysis…

Answer 11

• Always pathological process
• Causes the release of free haemoglobin into the plasma
• May be filtered by the kidneys
• Some is resorbed into tubular epithelial cells

Question 12

What is Haemoglobinaemia?

Answer 12

Release of free haemoglobin into the plasma

- Pink Serum

Question 13

What is Haemoglobinuria?

Answer 13

Haemoglobin in the urine

- Pink/ Orange urine

Question 14

What diseases can cause intravascular haemolysis?

Answer 14

• Complement- mediated immune reactions
• Damage to RBC membranes
• • Congenital defects
• • Some RBC parasites
• • Oxidative damage e.g cat eating garlic and onions

Question 15

Describe Haemosiderin…

Answer 15

• A breakdown product of Haemoglobin
• Yellow-brown pigment
• Insoluble storage form of iron
• Small amounts are normally found in macrophages of spleens
• Causes the yellow-brown colour seen in old bruises

Question 16

Describe the staining of Haemosiderin…

Answer 16

Pearls iodine or Prussian blue can be used to stain

Question 17

Where can local accumulations of haemosiderin found?

Answer 17

• Bruises (local haemorrhage)

- Areas of vascular congestion (heart failure cells)

Question 18

Where can systemic accumulations of haemosiderin found?

Answer 18

Haemosiderosis

• Systemic
• e.g. Cattle drinking iron rich bore water gives them orange organs
• Excessive haemoglobin breakdown
• Excessive dietary absorption
• Impaired Iron metabolism

Question 19

Describe Bilirubin…

Answer 19

• Derived from Haemoglobin
• Orange
• Transported to the bloodstream loosely bound to albumin
• Eventually excreted via bile into the faeces

Question 20

What happens if you have excessive bilirubin in the bloodstream?

Answer 20

Jaundice

• Causes yellow skin, sclera and mucous membranes
• The source of bilirubin may be:
• • Pre-hepatic
• • Hepatic
• • Post Hepatic

Question 21

Describe Pre-hepatic jaundice…

Answer 21

• Involves RBC breakdown
• • Immune- mediated disease
• • Incompatible blood transfusion
• • RBC parasites

NB: can be Intra or Extravascular

Question 22

Describe the normal pattern of Bilirubin metabolism?

Answer 22

Heme fragment > Bilirubin > Into Blood > Bound to albumin (carrier) > = Free bilirubin > Liver > Conjugated to glucuronic acid > = Conjugated bilirubin > Excreted in bile > Duodenum > Distal intestine > Oxidised by intestinal bacteria > Urobilinogens > Urobilin (urine) > Stercobilins (faeces)

Question 23

What does stercobilins do to faeces?

Answer 23

Makes it brown in colour

Question 24

What are the consequences of haemolytic jaundice?

Answer 24

• Increased levels of free bilirubin in the blood
• • This free bilirubin is toxic to developing neurons at high concentrations
• Anaemia
• With or without haemoglobinaemia & haemoglobinuria

Question 25

Describe Hepatic jaundice…

Answer 25

• Damage to hepatocytes results in decreased ability to conjugate with glucuronic acid and excrete bilirubin
• Free bilirubin levels in the blood increase
• Causes may be?
• • Leptospirosis
• • Viral hepatitis
• • Chronic Copper poisoning

Question 26

Describe Post-hepatic jaundice…

Answer 26

• Blockage of the bile duct system
• Impairs excretion of conjugated bilirubin
• Obstruction may be intra or extra-hepatic
• Causes may be?
• • Secondary to toxic jaundice
• • Blockage of bile duct by tumours, gallstones, inflammation etc.
• • Rupture of the bile duct

Question 27

What does cholestasis mean?

Answer 27

Stoping Bile

Question 28

What is a faecal sign of Post-hepatic Jaundice?

Answer 28

Pale faeces

- only a tiny amount of stercobilin is required to turn faeces brown

Question 29

Describe the blood tube of an animal with post-hepatic Jaundice?

Answer 29

• No excessive haemolysis
• Normal PCV levels
• Yellow Serum due to bilirubin

Question 30

Describe the blood tube of an animal with Hepatic Jaundice?

Answer 30

• No excessive haemolysis
• Normal PCV
• Yellow Serum due to bilirubin

Question 31

Describe the blood tube of an animal with pre-hepatic Jaundice?

Answer 31

• Excessive haemolysis
• RBCs lysed
• Low PCV
• Pink Stained serum
• Orangish urine

Question 32

Describe neonatal horse Jaundice…

Answer 32

If Mare and Stallion have different blood types

• Foal gets Stallion blood type
• After Foal is born and starts drinking colostrum from mum it will get jaundice as the Mare Colostrum Antibodies are directed against the Foals (stallion) blood RBCs
• RBCs lyse to produce jaundice in the foal