Chapter 1 (reading) Flashcards
the scientific study of microscopic structures of tissues and organs of the body
histology
What is the first step in preparation of a tissue or organ sample?
fixation to preserve the tissue for subsequent treatments
What is the most commonly used fixative?
formalin: 37% aqueous solution of formaldehyde
-combined with other chemicals and buffers
Formaldehyde preserves the general structure of the cell and extracellular components by reacting with:
amino groups of proteins (cross-linked lysine residues)
Why is formaldehyde a poor fixative of cell membranes?
it does not react with lipids
What is the second step of tissue preparation?
embedding in paraffin to permit sectioning
Preparing a specimen for examination requires its infiltration with an embedding medium that allows it to be:
thinly sliced
After fixation, the specimen is _____________and _________________ in a series of alcohol solutions to remove water.
washed and dehyrdated
What is function of clearing after dehydration of the tissue specimen?
organic solvents such as xylol or toluol remove the alcohol before infiltration of the specimen with melted paraffin
What is a microtome?
a specially designed slicing machine to cut the paraffin
a solution that hardens into a permanent mount that keeps the specimen attached to the glass and prevents deterioration of the specimen over time
mounting medium
What has to happen before the tissue specimen are stained?
the paraffin must be dissolved out with xylol or toluol and the slide must be rehydrated through a series of descending alcohol concentrations
The routine use of ____________as a fixative for electron microscopy is the primary reason for the excellent preservation of membranes in electron micrographs?
osmium tetroxide
the process in which radioactively tagged precursors of the molecule are incorporated by cells and tissues before fixation
autoradiography
What are the large macromolecular complexes that remain after fixation?
-nucleoproteins
-intracellular cytoskeletal proteins
-extracellular proteins
-membrane phospholipid-protein (carbohydrate) complexes
What are some examples of large molecules lost during routine fixation in aqueous fixatives?
glycogen, proteoglycans, and glycosaminoglycans
an acidic dye that carries a negative charge
eosin (NA+dye-)
carries a net positive charge on its colored portion
basic dye (dye+Cl-)basic
basic dyes react with ____________components of cells and tissue
anionic
What are the anionic components ?
-phosphate groups of nucleic acids
-sulfate groups of glycosaminoglycans
-carboxyl groups of proteins
the ability of anionic groups to react with a basic dye is called what?
basophilia
-an intermediate link between the tissue component and the dye
-causes the stain to resemble a basic dye
mordant
the reaction of cationic groups with an acidic dye is called what?
acidophilia
What three acidic dyes are used in the Mallory staining technique?
aniline blue, acid fuchsin, and orange G
the distance by which two objects must be separated to be seen as two objects
resolution
what is the function of the light source?
illumination of the specimen
what is the function of the condenser lens?
to focus the beam of light at the level of the specimen
what is the function of the objective lens?
to gather the light that has passed through the specimen
a defect caused by an error in the preparation process
artifact
what is the equation for resolution?
d= λ/NA objective + NA condenser
