Lecture 1 - intro Flashcards
what is cytology
study of the microscopic architecture of the cell
what is cytopathology
study of the microscopic architecture of the cell under disease conditions
what is histology
study of the microscopic architecture of tissue
what is histopathology
study of the microscopic architecture of tissue under disease conditions
what is an example of cytology
smear test
what is an example of histology
the cervical biopsy
what does hisotology use
microscope to identify patterns in the structure of normal tissue
what does histology allow you to understand
structure and architecture of the tissue
what can you use histology info for
identify what changes under PATHOLOGICAL conditions e.g. inflammation, infection
identify pathologic phenotypes and whether treatment can reverse this
what does the human tissue act regulate
use, storage, removal, activity and disposal of human tissue
post mortem specimens
what does THTA suggest
specimen use in histopathology requires consent
what are the 7 steps of histological staining
- tissue collection
- tissue fixation
- tissue processing
- tissue embedding
- microtomy
- tissue staining and mounting
-microscopy
when is tissue collected
post-surgery or post-mortem
what kind of record need to kept
histopathological records:
- date of specimen
-type of tissue - other findings of pathologist
how is tissue preserved
fixing
cryofreezing
why is fixation important
protects the tissue and the structures associated with it
what happens without tissue fixation
the tissue would rapidly broken down by the process of autolysis or putrefaction
how is fixation important for the biological analysis
- ensured it remains as similar to original tissue as possible
- preserves internal structures
- facilitates sectioning and staining by hardening tissue
what are the two prominent ways of tissue being fixed
heat
chemicals
what does chemical fixation include
denature proteins -> coagulative e.g alcohol and zinc
cross link membrane/ membrane proteins -> non-coagulative e.g. formaldehyde, osmium chloride
what are the advantages of formaldehyde
cheap, easy to prepare
good preservation
penetrates tissue easy
doesn’t cause excessive hardening
what are the disadvantages of formaldehyde
slow
inferior internal details
toxic
produces artifacts if blood in tissue
what external factors affect fixation
temperature (needs to be room temp)
sample size (1-5mm thick ideal)
time (24-48 hours ideal)
pH (close to neutral)
what happens after fixation
dehydration
what are the reagents of of dehydration
ethanol (70,90,100%)
isopropyl alcohol
what is the next step after dehydration
clearing
what is clearing
removing the alcohol from tissue to make it transparent
what is the reagent for clearing
xylene (mixes with ethanol and paraffin)
how many immersions is clearing done in xylene
3
is xylene toxic
yes
YOU GOT THIS
what happens after clearing
embedding
what does embedding do
encases the tissue in a supportive structure for sectioning
what is the reagent for embedding
paraffin
what dies embedding require
the correct platform and the tissue must be placed in the correct orientation for diagnosis
what happens after embedding
sectioning
what is sectioning
cutting the tissue
how is sectioning performed
using a microtome machine
what is the summarised process of sectioning
wax is trimmed away first
tissue is exposed and cut into thin sections
placed on cold water
placed on microscope slide
