Pigments and Lipids Flashcards
What are the 3 general classifications of pigments?
- Artefact- produced as a result of a chemical reaction in tissue
- Endogenous- produced within tissue/ are a by-product of normal metabolic processes
- Exogenous- gained access to body accidentally with no physiological function
List the pigments which are associated with artefact pigments
Formalin
Malarial
Mercury
Dichromate deposits
What is formalin pigment?
Brown/ black deposit following fixation in acid formalin, removed with picric acid
What is Malarial pigment?
formed in/ near RBC’s with parasite, mainly used if patient is infected with parasite
What is Mercury pigment?
Black deposit formed with fixaitves contianing Mercury, removed with iodine + sodium thiosulphate
What are dichromate deposits?
Yellow/ brown deposits after potassium dichromate foxation and insufficient washing prior to dehydration, removed with acid alcohol
List what endogenous pigments are comprised of
Bile pigments
Lipofuscin
Melanin
Iron
Calcium
Copper
Uric acid and Urates
What are bile pigments?
breakdown of RBC’s, red/brown bilirubin, green biliverdin, found in liver diseases or haemolytic disease
What is lipofuscin?
‘wear and tear’ pigment due to lipid oxidation, found near the nucleus, brown pigment stained by Sudan Black, PAS, Schorl’s, found in heat muscle, liver and the brain
What is melanin?
Product of melanocytes, brown/ black pigments, eye skin hair, brain and melanoma. Demonstrated by Masson Fontana
What are Iron pigments?
Stored as haemosiderin in ferric state (Fe3+), fine brow colour and found in liver, spleen and marrow, demonstrated by Perl’s Prussian Blue reaction
Describe haemosiderin
Iron-storage complex in cells/ tissues as opposed to circulating in the blood.
The iron is derived chiefly from the breakdown of erythrocytes
Very poorly available to supply Iron when it’s needed
What is Haemochromatosis?
A chronic condition when too much Iron is absorbed in the small intestine that impacts the liver and joints
The disease has a diverse disease pattern and presents in males aged 40-60 and in females after menopause
Patients have regular appointments to remove excess iron from the bloodstream
What is Haemosiderosis?
Reffered to as secondary haemochromatosis and is caused by blood transfusions or excessive iron medication
Less toxic than haemochromatosis and is treated with iron cheltating agents
What is the difference between Haemosiderin, Haemochromatosis and Haemosideris?
Haemosiderin: Iron-containing pigment formed from hemoglobin breakdown, stored in tissues.
Haemochromatosis: Genetic disorder causing excessive iron absorption and deposition in organs (liver, heart, pancreas).
Haemosiderosis: Iron accumulation in tissues due to chronic blood loss or transfusions, less severe than haemochromatosis.
What are calcium pigments?
Absorbed in GIT and demonstrated by Von Kossa and Alizarin
What are copper pigments?
Normally undetectable in histochemistry, demonstrated by Shikata Orcein, Rubenanic acid and Rhodanine
What are uric acid and urates?
Caused by excessive breakdown of nucleic acids and purine nucleotides. High uric acids are present in kidney diseases and crystallisation in the joints ids fund in gout.
List the features of a polarising microscope
Light source
Condenser- focuses light
Polariser 1- Polarises light, but only if the specimen is birefringent or contains birefringment structures
Objective- magnification
Polariser 2- crossed position to polariser 1
What are exogenous pigments comprised of?
Carbon
Silica
Asbestos
What is carbon, as an exogenous pigment?
Most common, absorbed by phagocytes, easy to identify but could be confused with melanin
What is Silica?
Can be birefringent, found in very inert angular masses, common in those who work in mines
What is asbestos?
The cause of fibrosis, long beaded fibres that become coated in protein sheaths containing heamosiderin demonstrated by Perl’s Prussian blue
How are fats and lipids defined?
By their solubility in fat solvents and their insolubility in water
