Histology Flashcards
For Skin (structure), give the Type of Structure and Type of Basic Tissue.
Type of structure = Organ
Type of basic tissue = Epithelial and Connective Tissues
For Fascia, Tendons, Aponeurosis, Muscle, Bone (structure), give the Type of Structure and Type of Basic Tissue.
Fascia = Organ/Tissue - Connective Tissue
Tendon = Organ/Tissue - CT
Aponeurosis = Organ/Tissue CT
Muscle = Organ/Tissue - Muscular Tissue
Bone = Organ/Tissue - Variety of CT
For Nerves (structure), give the Type of Structure and Type of Basic Tissue.
Type of Structrue = Tissue/Organ/System
Type of basic Tissue = Nervous Tissue
For Blood Vessels (structure), give the Type of Structure and Type of Basic Tissue.
Type of Structure = Organ/Tissues
Type of Basic Tissue = Epithelial, CT, Muscular
What is the equivalence between nm and Angstrom units?
1nm = 10 A
What is the average thickness of a section?
What is the average diameter of a cell?
What is the average diameter of a lysosome?
What is the average thickness of plasma membrane?
Section = 5um
Diameter of cell = 10um
Diameter of a lysosome = 200 nm
Thickness of PM = 75A (7.5 nm)
For a light microscope, what are the steps required for preparation of a tissue for microscopic examination?
- Chemical fixation (formalin)
- Dehydration (ethanol because Xylene and water don’t mix and Xylene is needed to allow proper infiltration of paraffin)
- Clearing (Xylene)
- Infiltration (Xylene/paraffin)
- Embedding (paraffin)
- Sectioning (microtome)
- Mounting (glass slide)
- Removal of paraffin (Xylene)
- Rehydration (100% ethanol → 100% H2O by steps)
- Staining (H&E) and/or histochemical reaction)
- Light microscopy
*Paraffin = Wax
For electron microscopy, what are the steps required for preparation of a tissue for microscopic examination?
- Chemical fixation (gluteraldehyde and osmium tetroxide)
- Dehydration (ethanol)
- Clearing (propylene glycol because it dissolves plastic)
- Infiltration (propylene glycol/plastic)
- Embedding (plastic)
- Sectioning (ultramicrotome)
- Mounting (copper grid)
- Staining (lead citrate and/or histochemical reaction)
- Transmission with EM
For a light microscope, what are the steps required for preparation of a tissue for microscopic examination when freezing the tissue instead of doing chemical fixation?
- Freezing
- Sectioning (cryostat)
From there, same steps: - Mounting (glass slide)
- Removal of paraffin
- Rehydration
- Staining (H&E)
- Light microscope
What does the dehydration step of tissue preparation involve?
Start with tissue in 100% H2O solution and step-by-step go to a 100% ethanol solution
1. 50% EtOH/50% H2O
2. 60% EtOH/40% H2O
3. 70% EtOH/30% H2O
…
*Do opposit for rehydration
What are the 2 main methods of chemical fixation?
*Fixation stops any biological process, freezes the organ in time
1. Perfusion = injecting a fix in the artery/circulation of the specimen freezing it inside-out
- Best to preserve resolution (faster)
- Used for EM or LM
- Immersion = anesthetize the specimen, remove the organ and immerse it into fix solution, fixing it outside-in
- for light microscope only
What solutions where/are used for Light miscroscopy fixation?
Before:
- Formalin (modifies nucleic acids)
- Mercuric Chloride (toxic)
- Pitric Acid (explosive)
Now:
Boin’s Fluid = Acetic Acid, Pitric Acid, Formalin (formaldehyde), Water
*For perfusion or immersion
What solutions are used for electron miscroscopy fixation?
Glutaaldehyde (2.5% - 5%)
What substances are used as paraffin solvent and epoxy solvents in tissue preparation for microscopy?
Paraffin solvent = Xylene (LM)
Epoxy (plastic) Solvent = propylene glycol (EM)
What are the most comon dyes in LM speciment preparation?
H&E:
1. Hematoxylin = basic dye
2. Eosin = acidic dye