Exam 1: Intro and Techniques Flashcards
What is histology
The study of tissues
Science concerned with the minute structure of cells, tissues, and organs in relation to their function
“Microanatomy”
Why do we need histology
Need to know fundamental tissues
Need to know what normal looks like so we can detect abnormal
Fundamental tissues
Epithelial
Connective
Muscular
Nervous
Steps in histology
Fixation - 10% formalin, Bouin’s
•Fix tissue in time
•Stop autolysis, prevent bacterial decomposition, stabilize proteins
Processing - alcohol, xylene, paraffin
Cutting - microtome
Mounting - glass slides
Staining - H&E, special stains
Cover slipping (preservation) and reading - resin and microscope
Stains - based on electrical charge
Acid or basic - most stains
Neutral - eg methylene blue picrate
Indifferent - eg Sudan III, Sudan IV (scarlet red)
Stains - supravital
Dead cells
As opposed to vital stains (live cells)
Routine stain
Hematoxylin and Eosin
Hematoxylin
Basic stain (+) attaches to (-) charges
Basophilic = stained by a basic stain (like H)
Cell nucleus - nucleic acids are (-) charged so get stained purple
Basic stains
Hematoxylin
Toluidine blue
Methylene blue (vital stain)
Fuscin stains
Eosin
Acidic stain (-) attaches to (+) charges
Eosinophilic = stained by acidic stain (like E)
Cell cytoplasm - cytoplasmic structures are (+) charged so get stained pink(ish)
Acidic stains
Eosin
Orange G
Phloxine
Aniline blue
Orientation of organ/tissue
Cross sections - cut cranial and caudal in half
Longitudinal sections - cut medial and lateral in half
Oblique to tangential sections - any other cut
Serial sections
4-5 microns thick
Used so you can used several different stains on the same area of tissue
Size estimation
Needed to describe and identify pathogens
Use RBC size to estimate •Dog - 5 microns •Goat - 2.5 microns •Chicken - 9.5 microns •Frog - 10-24 microns
Artifacts
Processing error or poor tissue quality
Example - freezing ice crystal artifacts - light pink color
Example - autolysis artifacts - looks like mush
Special stains used for…
Architecture - cell type, tissue type, tissue structure
Substances - normal or abnormal, intra or extracellular (matrix)
Pathogens - bacteria, protozoans, fungi
Polarization
Trichrome stains
Architecture
3 colors - 3 things to see
•color depends on tissue type
Masson’s, Mallory, etc.
Example: skin
•epithelial tissue on top is reddish
•collagen in middle is blue
•muscle on bottom is bright red
Wright-Geimsa stain and Diff Quick stain
Architecture
Good for impression smears, Blood smears, and Cytology
Orcein stain
Architecture
Elastic fibers
Dark brown color
Toluidine blue stain
Substances
Good for mast cell tumors
Methylene blue stain
Substances
Vital stain
Congo red stain
Substances
Polarizer
Finds amyloid - pink “lakes
With polarizer - apple green color
Prussian blue stain
Substances
Iron stains blue
AKA Pearl’s stain
Can be used to find iron in cells, or find iron in places it shouldn’t be
Gram stain
Pathogens - bacteria
Gram negative - red
Gram positive - blue/purple
