Introduction to Histology Flashcards
Name 5 types of biopsy.
- Needle
- Endoscopic
- Transvascular
- Direct excision
- Curettage
What are the preparatory steps for microscopy?
- Tissue Collection
- Fixation (dehydration, clearing)
- Embedding
- Sectioning
- Mounting/Staining
- Viewing
What is the goal of fixation?
Preserve tissue by preventing degradation. Maintains structure.
Name 4 fixatives (2 chemicals, 2 techniques).
Glutaraldehyde
Formaldehyde
Dehydration
Rapid Freezing
How do aldehydes (formaldehyde, glutaraldehyde) fix?
By crosslinking 3 amino groups and nitrogenous groups. Crosslinks every molecule within tissues, causing loss of biologic activity. Also prevents damage from unfriendly microbes.
What type of sample would you use dehydration to fix? What are the steps in this fixative process?
Dehydration used to fix monolayers of cells, or when tissue is readily available. Use a tissue of 80% alcohol for short periods of time.
What would you use for rapid freezing fixation?
Liquid isopentane at -160 degrees C.
Name 3 ways you could embed a sample (what would you use)?
- Paraffin wax
- Acrylic resin
- Freezing
How thin of slices can you section parafin wax? What viewing method is parafin wax used for? What is an advantage and disadvantage?
- 5-8 microns
- Light Microscopy
- Advantage: Good resolution of cell structure/tissues
- Slow (24 hours)
How thin can you section acrylic resin? What viewing method is acrylic resin used for? What are 2 disadvantages?
- 60nm to 1 micron.
- EM
- Incompatible with most histological stains, very slow (a few days).
How thick can you section frozen sections? What are 3 advantages of embedding by freezing?
12 to 20 micron sections.
- very fast
- can use immunological/histochemical stains
- maintains biologic activity when warm
Why do we stain samples?
Very little natural pigment. 90% water.
What does hematoxylin stain?
Hematoxylin stains acidic stuff blue. Stuff includes nucleic acids (nuclei, ribosomes, cartilage matrix).
What does eosin stain?
Eosin stains basic stuff pink. Stuff includes cytoplasm, collagen fibers.
What colors are the stains of Masson’s Trichrome? What do each color stain?
- Dark blue: nuclei,
- Red: muscle, keratin, cytoplasm (red meat, red nails)
- light blue: mucinogen, collagen (unlike eosin, which stains collagen pink).
What does Weigart’s stain stain? What color?
Elastic fibers, blue.
What does Silver stain stain? What color?
Neurofilaments, reticular fibers. Black.
What does iron hematoxylin stain? What color?
muscle (pump iron yo)
nuclei
erythrocytes (hemoglobin has iron yo)
Black.
What does Periodic Acid Schif stain? What color? Would it stain a Goblet cell?
PAS stains carbohydrate rich molecules (eg glycogen) magenta. It would stain goblet cells, which make mucinogen and contains mucopolysaccharides.
Why would you use Wright’s stain? How does Wright’s staining differ from HE staining? What colors, and what do each color stain?
To differentiate blood cells. Wright uses methylene blue instead of hematoxylin.
Pink: erythrocytes, eosinophil granules.
Blue: Nuclei of wbc, cytoplasm of monocytes/lymphocytes.
Total magnification of microscope= ____x____
objective lens magnification x ocular lens magnification
How small can human eyes resolve 2 points?
0.1-0.2 mm.
How small can a light microscope resolve 2 points?
.25 microns
How small can TEM resolve 2 points?
0.2 nm. Highest resolution so far.
