Histopath module 1 Flashcards
may vary according to: the structural
and chemical components of the cells to be examined or studied, the
nature and amount of the tissue to be evaluated, and the need for an
immediate examination of a tissue structure.
FRESH TISSUE EXAMINATION
process whereby selected tissue specimen is immersed in a watch
glass containing isotonic salt solution, carefully dissected or
separated, and examined under the microscope. Either unstained by
phase contrast microscope or bright field microscope or stained with
differential dyes.
Teasing or dissociation
is a process whereby small pieces of tissue not more than one mm. in
diameter are placed in a slide and forcibly compressed with another
slide or with a cover glass
SQUASH PREPARATION
process of examining sections or sediments, whereby cellular
materials are spread lightly over a slide means of a wire loop. This
technique is especially usefully in cytological examinations,
particularly for a cancer diagnosis.
SMEAR PREPARATION
THREE WAYS OF SMEAR PREPARATION
- STREAKING
- SPREADING
- PULL APART
with an applicator stick, the material is rapidly and gently applied in
direct or zigzag line throughout the slide
STREAKING
has the advantage of maintaining a cellular inter relationships of the
material to be examined. It is especially recommended for smear
preparations of fresh sputum and bronchial aspirates and also for
thick mucoid secretions.
SPREADING
- useful for preparing smears of thick secretions such as serous fluids,
concentrated sputum and blood smears.
PULL APART
- for rapid diagnosis, especially recommended when lipids and nervous
tissue elements are to be a demonstrated
FROZEN SECTIONS
COMMONLY USED METHOD IN FREEZING TISSUE
Liquid nitrogen
* Isopentane cooled by nitrogen
* Carbon dioxide gas
* Aerosol sprays
10 STEPS IN PROCESSING TISSUE
- FIXATION
- DEHYDRATION
- CLEARING
- INFILTRATION (IMPREGNATTION)
- EMBEDDING
- TRIMMING
- SECTION-CUTTING
- MOUNTING
- STAINING
- LABELLING
First and most critical step in histo technology involves fixing or
preserving fresh tissue for examination.
FIXATION
to preserve morphologic and chemical integrity of the
cell in as life like a manner as possible.
PRIMARY AIM
: harden and protect the tissue from the trauma of
further handling.
SECONDARY GOAL
It is also prevents degradation decompositions , putrefaction and
distortion of tissue after removal from the body.
SECONDARY GOAL
TWO BASIC MECHANISM INVOLVED IN FIXATION
ADDITIVE FIXATION? NON ADDITIVE
fixatives is taken in and becomes part of the tissue by forming cross- links or molecular complexes and gibing stability to the protein
. ADDITIVE FIXATION
whereby the fixing agent is not incorporated into the tissue, but
ALTERS the tissue composition and stabilizes the tissue by removing the
bound water attached to H-bonds of certain groups within protein
molecule
. NON ADDITIVE FIXATION
MAIN FACTORS INVOLVED IN FIXATION
Hydrogen Ion concentration
temperature
thickness of sectioN
osmolalitY
concentrations
duration of fixations
Hydrogen Ion concentration ph?
ph must be 6 -8
temperature
for surgical specimens?
room temp
For elctron microscopy and histochemsitry
0-4 deg cel
osmolality
should be slightly hypertonic solutions
400-459 mOsm. Isotonic are 340 mOsm
PRACTICAL CONSIDERATIONS OF FIXATIONS
SPEED
PENETRATION
VOLUME
duration of fixation
