Minerals and Pigments Flashcards
What is a pigment?
A coloured opaque substance present in cells or tissues
List the three main forms of pigment.
Artefact
Endogenous
Exogenous
Artefact pigments are mostly due to __________ _________.
Chemical fixation
True or false: formalin may leave brown artefact pigment.
True
What is an endogenous pigment?
Pigments formed in the body, and can be distinguished as hematogenous pigments such as bile, and non-haematogenic pigments such as melanin, or lipofuschin
Endogenous pigments are formed within the cell where they have a physiological role or are by-products of _______________.
Metabolism
____________ are observed as yellow-brown intracellular granules inside cells.
Haemosiderins
What stain is used to demonstrate haemosiderins?
Perl’s Prussian Blue
List one condition in which excessive haemosiderins may be observed.
Haemochromatosis
After ageing red cells are broken down by the reticuloendothelial system, the iron is removed from haemoglobin and the result is the formation of ____________.
Biliverdin
Biliverdin is converted to ______ in liver and is stored as bile within the gallbladder.
Bilirubin
‘_______ __________’ refers to bilirubin, biliverdin and haematoidin.
Bile pigment
List two scenarios in which an excess of bile pigments may be found.
Bile duct obstruction
Abnormality of bilirubin biliverdin metabolism
With H&E stain, bile pigments appear as __________-_______ ___________.
Yellow-brown crystals
Bile pigments are identified using the ________ reaction.
Fouchet
State the principle of the Fouchet reaction.
Ferric chloride oxidises all bile pigments to green biliverdin.T his oxidation reaction is rapidly accomplished by ferric chloride in trichloroacetic acid medium (Fouchet’s reagent). Biliverdin is then stained emerald green by acid fuchsin in van Gieson solution.
List two non-haematological pigments.
Lipidic, such as lipofucsin, and non-lipidic, such as melanin
________ is a wear-and-tear pigment.
Lipofucsin
_________ ______________ is excessive storage of lipofucsin.
Ceroid lipofuscinosis
What is melanin?
A pigment produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization
Melanin pigments are produced in a specialized group of cells known as ______________.
Melanocytes
Melanin is normally found in the ______.
Skin
____________ DOPA is an intermediary pigment of melanin.
Tyrosine
Melanin is produced by melanocytes in the epidermis and in skin phagocytes called ‘melanophages’ during ______________.
Inflammation
Melanin production is observed in the _________ ______, the iris, and also in melanomas of the eye.
Ciliary body