MOD 1 UNIT 1: INTRODUCTION TO HISTOLOGY Flashcards
to preserve a section of tissue or organ for histologic examination
FIXATION
most commonly used fixative for light microcopy is
formaldehyde
After the tissue specimen is fixed, which is usually overnight, water must first be
removed from the fixed specimen
POSTFIXATION
Before the specimen can be
embedded in a paraffin (wax) medium for cutting, it must be cleared of alcohol by passing
it through several changes of such clearing agents as?
xylene
The paraffin
block is then trimmed to the size of the specimen and mounted in an instrument called
microtome
precisely advances the paraffin block so that the sections are
cut at specific and predetermined increments with a steel knife.
microtome
For histologic examination
of the specimen, the sections are normally cut at
5 to 10 mm thickness
serves as an adhesive
medium for the specimen
albumen
allows for
viewing of the stained specimen on the glass slide with the light microscope.
coverslip
Structures in the specimen that stain most readily with basic stains are called
basophilic
those that stain with acidic stains are called
acidophilic
most
common stains that are used for histologic sections are
hematoxylin and eosin stains
small pieces of tissue are placed in solutions of chemicals that cross-link proteins and inactivate degradative enzymes
fixation
tissue is transferred through a series of increasingly concentrated alcohol solutions, which removes all water
dehydration
alcohol is removed in organic solvents in which both alcohol and paraffin are miscible
clearing
tissue is then placed in melted paraffin until it becomes completely infiltrated
infiltration
paraffin-infiltrated tissue is placed in a small mold with melted paraffin and allowed to harden
embedding
the resulting paraffin block is trimmed to expose the tissue for sectioning (slicing) on a microtome
trimming
an epithelial cell that has a flattened shape, they are seen in sections cut edgewise so they appear very thin, and you see
the flattened nucleus
squamous
an epithelial cell with equal height and width
cuboidal
an epithelial cell with the height distinctly greater than the width
columnar
These terms describe ball-shaped or egg-shaped cells
spherical or ovoid
These cells are elongated and tapering at the two ends
fusiform
Multiple flattened surfaces give the appearance of a pentagon, hexagon, and so
on
polyhedral
These cells have a distinct orientation with one end of the cell being different from
the other
polarized
The cell that appears to have vacuoles
filling the apical two thirds of its cytoplasm, a mucus-secreting cell
goblet cell
These vesicles stain because they retained at least some of their contents
during tissue preparation
granules
This type of cytoplasm contains what appear to be empty
holes. Usually, these represent either lipid droplets or vesicles whose contents were washed
out during processing of the tissue.
Vacuolated cytoplasm
TRUE OR FALSE
Cells that are inactive in protein synthesis will usually have fairly large nuclei,
prominent nucleoli, and a preponderance of euchromatin.
FALSE
“active”
TRUE OR FALSE
Nuclei of most cells show us a mixture of euchromatin
(dispersed, lightly stained, accessible to transcription) and heterochromatic (condensed,
darkly stained, inactive).
TRUE
TRUE OR FALSE
Typically, nucleoli are present in a nucleus that has most of its chromatin in
the form of euchromatin
TRUE
TRUE OR FALSE
A simple nucleus appears as a double structure that can have
a variety of shapes (round, oval, indented, fusiform, and irregular).
FALSE
“single structure”
TRUE OR FALSE
segmented nucleus,
appears in sections as two or more distinct parts (lobes)
TRUE
TRUE OR FALSE
many cells are not compact spheres or simple geometric shapes but have other shapes
that can be extremely complex
TRUE
Uses ordinary light & the
colors are imparted by tissue
staining
Bright-field microscopy
often used to image specific features of small specimens such as microbes
fluorescence microscopy
optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image
Phase-contrast
Microscopy
provides the ability to collect clear images from a thin section of a thick sample with low background and minimal out-of-focus interference
Confocal microscopy
detection method in which X-ray or photographic film is exposed to emissions from radioisotopes on TLC plates to produce an image on the film.
Autoradiography
type of inverted microscope where the light source is placed above the specimen rather than shining from below
Tissue culture microscopes
used to demonstrate the activity of enzymes present on tissues
Enzyme Histochemistry
a powerful technique that exploits the specific binding between an antibody and antigen to detect and localize specific antigens in cells and tissue
Immunohistochemistry (IHC)
utilizes an unlabeled primary antibody to detect the antigen of interest in the tissue
Indirect immunohistochemistry
