Overview of histological techniques Flashcards
What is the first step that enables preservation of tissue structure?
Cut up and fixation
Tissue pieces must be cut small enough to allow ____ ____.
Chemical fixation
Allows the fixative to penetrate readily
What step occurs after fixation?
Tissue processing
What is the purpose of tissue processing?
To replace the water in the tissue with paraffin wax
What is the purpose of replacing the water in a tissue with paraffin wax?
Paraffin wax is a more rigid structure at room temperature so helps the tissue hold its shape when generating thin sections for staining
What are the properties of xylene relevant to tissue processing?
Xylene is a hydrophobic solvent which mixes with paraffin wax and assists in replacing the water in a tissue with paraffin wax
What occurs in a tissue processor?
Under pressure a series of increasing concentrations of alcohol and xylene are pumped into the chamber to remove the water from the tissue and replace it with paraffin wax
What is the approximate time frame commonly used for tissue processing?
A four to six hour cycle, often set to be performed overnight
What step occurs after tissue processing?
Embedding
What temperature are the processed tissue cassettes kept at prior to embedding?
63’C
What temperature is the plate that cassettes are placed on following embedding?
-4’C
What step occurs after embedding?
Microtomy
What is the purpose of microtomy?
Generating thin sections of tissue that can be mounted on glass slides for staining and microscopy
What is done with glass slides that have picked up a tissue section from the water bath after microtomy?
The slides are baked in an oven to bond the tissue to the surface of the slide
What step occurs after baking the tissue section onto a glass slide?
“Taking sections to water”
What is the purpose of taking sections to water?
Taking sections to water removes the paraffin wax and rehydrates the tissue
How is the paraffin wax removed from the tissue?
The slide is immersed in two changes of xylene then the tissue is rehydrated by passing it through decreasing concentrations of alcohol and finally placing them in the water bath
What step occurs after taking sections to water?
Staining
What is the purpose of staining?
Staining structures of interest to visualise different tissue components
Most tissue stains are either dissolved in ____ or are combination of ____ and ____.
Water; water; alcohol.
What step occurs after staining?
Dehydration and clearing
What is the purpose of dehydration and clearing?
<p></p>
<p>Removal of water from the tissue in preparation for mounting in plastic</p>
How is the tissue dehydrated following staining?
The slide is passed back through the same coupling jars of alcohol and xylene
What step occurs following dehydration and clearing?
Mounting in a plastic mounting medium
What is the final step of histology slide preparation?
Mounting in a plastic mounting medium
What substance is the plastic mounting medium dissolved in?
Xylene
Should a histology slide be allowed to dry out prior to mounting in plastic mounting medium?
No - some xylene must be present on the slide to mix with the mounting medium
Name the process by which tissue structure is preserved
Fixation
Name the process by which thin sections of tissue are created
Microtomy
Name the process by which tissue is oriented in preparation for sectioning
Embedding
Name the process by which the water within tissue is replaced with paraffin wax
Processing
Name this piece of equipment
<br></br>
<br></br><p style="text-align:center;"></p>
Tissue processor
Name this piece of equipment
<br></br>
<br></br><p style="text-align:center;"></p>
Embedding station
Name this piece of equipment
<br></br>
<br></br><p style="text-align:center;"></p>
Microtome
Name feature A of this piece of equipment
Processing chamber