Test One Flashcards
(48 cards)
Three basic steps of tissue preparation?
1) Fixation
2) Infiltration
3) Stain
Characteristics of Fixation
- Formalin is most common
- Formaledhyde cross links amino groups of proteins, ‘fixing’ their positions
Characteristics of Infiltration
- Paraffin is the most common
- It requires washing out the formalin with water, dehydration with alcohol to remove water and clearing with xylol to remove alcohol
Hematoxylin color
Blue
Eosin color
Red
What binds to hematoxylin?
Nuclear DNA and cytoplasmic RNA
What binds to eosin?
Cytoplasms and extracellular fibers
What retains lipids?
Frozen sections
What does methylmethacrylate do?
Improves resolution and/or accommodate special stains
Periodic Acid-Schiff Reaction
- stains carbohydrates
- useful to demonstrate glycogen, mucus, basement membrane and reticular fibers
- positive sites stain a magenta color
Feulgen Reaction
- Produces an acid hydrolysis
- Useful to stain DNA, not RNA
- Reaction is stoichiometric
- Positive produces a magenta color
Fluorescent Dyes
- AKA fluorochromes
- Fluoroscein is the most commonly used fluorochrome
- Fluoroscein absorbs UV light and emits green light
Enzymatic Histochemistry
- Localizes an enzyme in tissues by its reaction product
- A capture agent that can be visualized with a microscope is used to bind to the product, thereby localizing the enzyme.
- Lead ions are commonly used as a capture agent
Simple Microscope
One lens
Compound Microscope
More than one lens
Resolving power (R.P.)
The distance by which two objects must be separated to be seen as two objects
Bright Field Light Microscope
- most commonly used
- requires fixation and staining
Phase contrast light microscope
- depends on differences in the refractive index of cell components; denser areas appear as darker images
- enhances contrast without staining, allowing the study of living cells and tissues
Polarizing light microscope
Useful to locate structures with highly ordered, repeating molecules, such as collagen and actin.
Confocal light microscope
Utilizes lasers and reconstruction computer software to form a three-dimensional, layer-by- layer image that can be rotated and viewed from any orientation
Transmission Electron Microscopes (TEM)
- image appears as shades of grey on a phosphor-coated screen
- bright areas allowed the electrons to pass through / dark areas absorbed or scattered the electrons
- tissues are embedded in methylmethacrylate polymer
- tissue placed on copper grids, not glass slides
Scanning Electron Microscope
- an electron beam scans the surface of a specimen
- reflected electrons are collected and processed to form a three-dimensional-like image on a cathode ray tube
Atomic Force Microscope
- useful to image the surface topography at molecular and atomic resolution
- A cantilevered laser sensor either touches the surface or taps across it
- Does not require a vacuum (unlike TEM and SEM) which therefore allows imaging of living tissues with an AFM
Four primary types of body tissues
1) epithelium
2) connective tissue
3) nervous tissue
4) muscle
