Basics Flashcards
What is point-to-point resolving power if a light microscope best between
What is it restricted ultimately by
Between 0.1um to 0.2um
Wavelength of visible light
How is the ability to resolve bacteria
Mostly
Range in size from 1um to 10um diameter
How is the ability to resolve cell organelles
Larger ones
E.g.
Nuclei (6um D)
Mitochondria (1um D)
Secretion granules (0.5-1um D)
Cannot see e.g. ribosomes or cytoplasmic vesicles
How is the ability to resolve membranes
Sometimes
Too thin to be seen in isolation - become visible in high concentrations of extracellular material or cytoplasmic contents bound to them and are appropriately stained
How is the ability to stain cells
Almost always
Both cytoplasm and nucleus can normally be clearly delineated
How is the ability to stain extracellular material
Sometimes
Can be stained - collagen and elastin
Cannot be stained (invisible) - hydrophilic molecules e.g. GACs
How are specimens prepared for microscopic examination
Fixed - chemical such as formalin, alcohols or acids which cross-link or precipitate cell constituents rendering them insoluble and preserving them
Embedded - dehydrated with alcohol and embedded (infiltrated) with liquid wax or plastic resin which are subsequently solidified.
Sectioned (sliced) - Permits tissue to be cut into slices 2-10um thick which is thinner than the diameter of most cells
Stained - wax-encasing dissolved away, specimen re-hydrated. Water-soluble or alcohol-soluble dyes
What is formalin
Aqueous solution of formaldehyde
What cells are extracted during the embedding process
Lipids - major components of cell membranes and adipose (fatty tissue)
Alcian Blue
Structures stained?
Colour
GAG-rich structures - Blue
Mucous goblet cells - Blue
Mast cell granules - Blue
Cartilage matrix - Blue
Eosin
Structures stained?
Colour
Colloidal proteins (e.g. plasma) - Pink
Keratin - Orange/red
Iron Haematoxylin (Not routinely used in diagnostic practices)
Structures stained?
Colour
Nuclei - Black
Elastic fibres - Black
Haematoxylin
Structures stained?
Colour
Nuclei - Blue
RNA - Blue
Periodic Acis Schiff (PAS)
Structures stained?
Colour
Hexose sugars - especially those contained in complex carbohydrate containing structures including goblet cell mucins, cartilage matrix, glycogen, basement membrane, glycocalyx
Magenta (dark pink)
Perl’s stain
Structures stained
Colour
Ferric Iron - prussian blue
