1. Introduction Flashcards
What is disease?
A pathological condition of a body part, an organ, or a system characterised by an identifiable group of signs or symptoms
What is tissue autolysis?
Self-digestion which begins when the blood supply is cut off
It destroys cells and tissue architecture
How do you block autolysis?
Fixatives
- inactivate tissue enzymes ad denature proteins
- prevent bacterial growth
- harden tissue
What is fixation?
Hold tissue in suspended animation
Usually use formalin (formaldehyde)
Penetrates tissue at approximately 1mm/hr
Usually fix for 24-48 hrs
How is the tissue made hard enough to cut thin slices?
Surrounded and impregnated with hardening agent - paraffin wax
How is water removed from the tissue?
Dehydration using alcohol in a vacuum so that water is drawn out of cells
Then replace alcohol with xylene which can mix with wax
Then replace xylene with molten paraffin wax
How are thin sections cut?
Using a microtome
Thin wax sections are floated on water bath and picked up on microscope slide
What stain is usually used?
H&E
Haematoxylin stains nuclei purple
Eosin stains cytoplasm and connective tissue pink
What is immunohistochemistry?
Demonstrates substances in/on cells by labelling them with specific antibodies
Usually the antibody is joined to an enzyme that catalyses a colour-producing agent
Highlight substances usually with brown colour
What are cytokeratins in immunohistchemistry?
Intracellular fibrous proteins
Present n almost all epithelia
Markers for epithelial differentiation and show tissue-specific distribution in epithelia
Can give information about primary site of carcinoma
When are frozen sections used?
When tissue needs to be hardened quickly
Intra-operative
Takes about 10-15 mins
Establishes presence and nature of a lesion and influence course of the operation
