Flashcards in ToB 1 Microscopy Deck (41)
The study of the structure of tissues by means of special staining techniques, combined with light and electron microscopy.
A collection of cells specialised to perform a particular function. Aggregations of tissues constitute organs.
State the value of histology in diagnosis:
Often the final proof of a diagnosis, and may type the disease and/or inform therapy.
State the relationship between mm and um:
1mm = 1000um
What is the average diameter of most cells (in um)?
~ 10-20 um
The removal of a small piece of tissue from an organ or part of the body for microscopic examination.
Name the 4 types of tissues:
Name the 6 types of biopsies:
3) Direct Incision
What is a 'smear' biopsy?
Spontaneous/mechanical exfoliation to collect cells.
What type of tissues can you biopsy via smear?
Buccal and cervical cavities
What is a 'curretage' biopsy?
The use of a small scoop to remove cells.
What types of tissues can you biopsy via curettage?
Endometrial lining of the uterus.
What is a 'needle' biopsy?
The insertion of a needle into tissue to remove cells.
What types of tissues can you biopsy via needle?
Brain, breast, liver, kidney, muscle
What is a 'direct incision' biopsy?
An incision directly into the tissue of interest, and removal of tissue.
What types of tissue can you biopsy via direct incision?
Skin, mouth, larynx
What is an 'endoscopic' biopsy?
Removal of tissue via instruments using an endoscope.
What types of tissue can you biopsy via endoscope?
Lungs, intestine, bladder
What types of tissue can you biopsy using a transvascular approach?
Why do tissues need to be fixed for microscopy?
To preserve the structure, and to prevent autolysis and putrification.
What fixatives are commonly used for fresh biopsies?
Why can tissue processing lead to shrinkage artefacts?
During processing the slide is dehydrated then rehydrated, which can lead to abnormalities in final slide.
Why can't a fresh biopsy be put directly into wax for slide preparation?
Fresh biopsies contain a lot of water, which cannot be placed into wax.
What is used to dehydrate a fresh biopsy?
Why is a biopsy sample embedded and impregnated with wax?
To allow the biopsy to be sliced thinly and placed onto microscope slides.
Why is a biopsy sample rehydrated once it has been sliced and placed onto a slide?
To allow staining (most stains are water-soluble), which allows the study of cell presence and structure.
What is used to fix the stained biopsy permanently?
Once the biopsy has been dehydrated using ethanol, what is used to clear the ethanol?
Xylene or Toluene
An artificial structure or tissue alteration on a prepared microscope slide, as a result of an extraneous factor
What are the 2 most common stains used in histology?
1) Periodic Acid-Schiff reaction
2) Haemotoxylin and Eosin stain
What components of the cell does the Periodic Acid-Schiff stain, and what colour?
Carbohydrates and glycoproteins are stained magenta.
Which stain colours goblet cells magenta?
The periodic acid-schiff stain
In terms of staining, what does PAS stand for?
What stain is used to colour DNA and RNA purple/blue?
What stain is used to colour basic cell components pink?
What is the Hematoxylin-Eosin stain used for?
To colour acidic cell components purple/blue, and basic cell components pink.
What are 3 advantages of using phase-contrast microscopy?
1) Use to study live cells in their natural state
2) Creates enough contrast to view transparent cells, which cannot be viewed via light microscopy
3) High contrast, high resolution
What are 3 advantages of dark-field microscopy?
1) Use to study live cells in natural state
2) Can use to study transparent cells
3) Highlights structures around the nucleus/cell membrane (as creates image from scattered light)
What type of microscopy is used to identify syphilis and malaria bacterium's?
What is the main advantage of fluorescence microscopy?
Allows certain cell structures to be labelled with fluorochromes, and the study of these under UV light.