Session 1 Flashcards
Define disease
Pathological condition of a body part, organ or system characterised by an identifiable group of signs or symptoms
What is pathology?
The study of suffering (disease and cellular dysfunction)
Cytopathology involves the study of…
Disaggregated cells rather than tissues to study disease
Histopathology involves the study of…
Tissues to study disease
Give examples of histologcal procedures (3)
Core biopsies
Cancer resection specimens
Excised skin lesions
Give examples of cytological procedures (2)
Fine needle aspirates of breast/thyroid/salivary glands
Cervical smears
Give 2 advantages of histological investigations/procedures over cytological investigations/procedures
Often therapeutic as well as diagnostic
Can assess architecture as well as cell atypia
Give 3 advantages of using cytological procedures/investigations over histological procedures/investigations
Faster and cheaper
Non-invasive or minimally invasive
Can be used for cells in fluid
The staging of cancer often follows the TNM system which looks at…
Tumour
Nodes
Metastases
What is autolysis? How can this affect microscopy of a tissue?
Self digestion of a tissue which occurs when the blood supply is cut off
Destroys cell and tissue architecture
How can autolysis be prevented?
By use of fixatives that inactivate tissue enzymes, prevent bacterial growth and harden the tissue
What chemical is typically used in fixation of sample for microscopy? What change in appearance will the tissue show after the fixative is applied?
Formalin
Raw meat —> Cooked meat
Tissues that have been fixed are placed into a ________ with holes in it to allow the chemical to penetrate the sample
Cassette
Why is it important for the tissue to be hard? What is this process called?
Allows the tissue to be cut into very thin slices
Embedding
What is commonly used as the hardening agent when a tissue is embedded?
Paraffin wax
Outline the process of embedding a tissue
Dehydration using alcohol in a vacuum
Alcohol replaced with xylene as it can mix with wax
Xylene replaced with molten paraffin wax
Tissues are typically cut to what thickness? Using which piece of equipment?
~3-4 microns
Microtome
What stain is most commonly used to stain samples?
H & E stain
Haematoxylin + Eosin
What does haematoxylin stain the most?
The nucleus most strongly blue
What does eosin stain the most?
The EM (cytoplasm and connective tissue) most strongly pink
What is the purpose of mounting a slice of tissue?
Preserves and protects the sample
What does immunohistochemistry involve?
Demonstrates substances in/on cells by labelling them with specific antibodies. These antibodies are usually linked to an enzyme that catalyses a colour-producing reaction.
What are cytokeratins? What is the clinical significance of these?
Family of intracellular fibrous proteins present in epithelial cells
They are markers for epithelial differentiation and show a tissue specific distribution in epithelia. So they can be used to show whether a cancer is a carcinoma and its primary site depending on the combination of different cytokeratins found
Why are frozen sections sometimes taken?
It’s a method of hardening tissue quickly - useful intra-operatively as it gives a quick result and can influence the course of the operation