Pigments

Question 1

Gernal pigments

Answer 1

Exogenous and endogenous substances can alter the colour of tissues. The colour change can be evident clinically or macroscopically at autopsy = can be diagnostically useful

Question 2

Carbon and other dusts

Answer 2

Exogenous pigmented substances

Carbon in lungs = black colour - anthrcosis

Question 3

Carbon and other dusts –>Low exposure

Answer 3

Low exposure = eg polluted air, not associated with clinical disease, impart a fine grey-black stippling to the lungs.

Question 4

Carbon and other dusts –> Histologically

Answer 4

indigested carbon particles = fine black granular material and crystalline material in macrophages in extracellular tissues (located next to intrapulmonary airways and vasculature)

Question 5

Carotenoid pigments

Answer 5

Exogenous pigmented substances
Abundent in leafy green plants = yellow discolouration to plasma, adipose tissue and other lipid-laden cells.

Deep yellow colour of adipose tissue in herbivores on lush green pasture can be striking.
- maybe why the cow has yellow fat

Discolouration is not a lesion just dietary indicator

Question 6

Melanin

Answer 6

Nonhaematogenous endogenous pigment
Pigment of hair, skin and iris
Can have black faced sheep, cattle, oral mucosa

not a lesion, not a response to to injury, no ill effect

Histologically
melanin granules are small, dark brown to black and nonrefractile.

pathology can increase or decrease melanin

Question 7

Lipofuscin

Answer 7

Nonhaematogenous endogenous pigments
A yellow-brown lipoprotein accumulates as residual bodies in secondary lysosome

Prominent in long-lived post-mitotic cells, such as neurone and cardiac mycoses and especially in aged animals

Aka - “wear and tear” pigment of ageing and has no effect on cell

Histologically, lipofuscin
Yellow- brown, finely granular cytoplasmic pigment

Question 8

Haemosiderin

Answer 8

Haematogenous pigments (derived from erythrocytes)
haemoglobin-derived
Golden yellow-to-brown

Major storage from irons
In cells iron is stored in association with the protein apoferritin = to form ferritin micelles

Normally only seen in mononuclear phagocytes of bone marrow, spleen and liver ( which all have major active roles in cell breakdown)

During haemorrhages in tissue there is an abnormal excess accumulation of iron, eg common bruise

• local or systemic excess of iron, Ferritin forms
• there is the formation of haemosiderin granules

Question 9

Bilirubin

Answer 9

Haematogenous pigments
Normal = low amounts in the plasma as erythrocyte breakdown product, by macrophages.

Process of breakdown of erythrocytes
globular proteins = broken down into amino acids
Heme with iron removed then oxygenase—> biliverdin then reductase—> bilirubin
Then moved in blood as albumin-bilirubin complex in blood —> then conjugation with glucuronic acid
Then secreted into the bile canaliculus

Abnormal (icterus or jaundice)
Prehepatic = increased turnover of erythrocytes = too much unconjugated bilirubin, the liver cannot handle
Hepatic = heaptocellular injury = decrease uptake, conjugation or secretion of bilirubin
Posthepatci = reduced outflow of bile from liver into intestine via billary system secondary to an abstraction

Histology
- icterus not observed histologically