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
Melanin production is ound in the substantia niagra of the ________, with reduced amounts in Parkinson’s disease.
Brain
Define ‘melanoma’.
Abnormal growth of skin cells, which most often develops on skin exposed to the sun
List three forms of skin cancer.
Basal cell carcinoma
Squamous cell carcinoma
Melanoma
Sometimes, melanoma develop from a _______ with concerning changes including an increase in size, irregular edges, change in colour, itchiness, or skin breakdown.
Mole
The primary cause of melanoma is __________ ______ exposure in those with low levels of skin pigment.
Ultraviolet light
Name a genetic defect which increases the risk of developing melanoma.
Xeroderma pigmentosum
How is melanoma diagnosed?
Skin biopsy of the subject lesion
True or false: melanoma is the least concerning form of skin cancer.
False
Describe the Argentaffin reaction.
Granules with melanin bind and reduce silver ions via Masson Fontana stain, and
granules reduce ferric ferricyanide via Schmorl’s stain
Melanoma can be bleached with ____________ ________________
Potassium permanganate
State one monoclonal antibody which can be used in visualising melanoma.
S100
What is HMB45?
An antigen on melanosomes
List two other methods of melanoma histochemistry visualisation.
Enzyme methods, such as DOPA reaction
Fluorescent methods
State the principle of Schmorl’s reaction.
Melanin will reduce ferricyanide to ferrocyanide with the production of Prussian blue, in the presence of ferric salts
Cells that are capable of producing melanin can be demonstrated by the __________________ (DOPA) method.
Dihydroxyphenylalanine
The enzyme __________, localized within cells, will oxidise DOPA to form an insoluble brown black pigment.
Tyrosinase
Melanins are insoluble in most ________ solvents due to tight bonding with proteins.
Organic
What is vitiligo?
An acquired pigmentary disorder of the skin and mucous membranes
____________ is characterized by depigmented macules and patches.
Vitiligo
Superficial perivascular and perifollicular lymphocytic ____________ may be observed at the margin of vitiliginous lesions.
Infiltrates
True or false: vitiligo is frequently associated with disorders of autoimmune origin, with thyroid abnormalities being the most common.
True
_______ amounts of copper are found normally in some tissues.
Small
Where are increased copper deposits found in Wilson’s disease?
Brain, liver, and eyes
Liver staining for copper with ________ ____ shows red brown granules in hepatocytes.
Rubeanic acid
What causes Wilson’s disease?
A mutation in the Wilson disease protein (ATP7B) gene
The ATP7B protein transports excess copper into ______, where it is excreted in waste products.
Bile
Normal stores of _______ are found in bone marrow, liver, and spleen.
Iron
Abnormal deposits of ___________ can be associated with atherosclerosis, sarcoid, necrotic tissues in TB infection, some tumours, and in joints in chondrocalcinosis.
Calcium
What is the von Kossa method?
An indirect way of detecting calcium, where silver nitrate replaces the carbonate anions of calcium salts (silver substitution method). Sunlight reduces the silver salt to visible metallic silver, and unreduced silver is removed by sodium thiosulphate
What colour do calcium deposits appear as?
Black
__________ is commonly inhaled, ingested or implanted in skin following industrial exposure.
Carbon
How can melanin be distinguished from carbon?
Melanin’s colour will disappear with bleaching, but carbon’s colour will remain
Asbestos fibres are ____________ fibres of magnesium silicate.
Birefringent
Where do asbestos fibres collect?
In alveoli at periphery of lung
Asbestos fibres have a ___________ ______, which contains haemosiderin.
Proteinaceous coat
____________ pigments are found in the skin and adjacent lymph nodes of various colours of the dye pigments seen.
Tattoo
Lugol’s iodine, picric-alcohol, and potassium permanganate bleach are reagents used to __________ pigments.
Remove
What stain is used to demonstrate asbestos fibres?
Perl’s Prussian Blue
