Pigments Flashcards
Gernal pigments
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
Carbon and other dusts
Exogenous pigmented substances
Carbon in lungs = black colour - anthrcosis
Carbon and other dusts –>Low exposure
Low exposure = eg polluted air, not associated with clinical disease, impart a fine grey-black stippling to the lungs.
Carbon and other dusts –> Histologically
indigested carbon particles = fine black granular material and crystalline material in macrophages in extracellular tissues (located next to intrapulmonary airways and vasculature)
Carotenoid pigments
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
Melanin
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
Lipofuscin
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
Haemosiderin
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
Bilirubin
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