Intro to Histology Flashcards
What is histology?
Study of the microanatomy of cells, tissues and organs as seen through a microscope.
What is a tissue?
Groups of similar cells working together to carry out a common function.
Cells + ECM
How can tissues be classified?
- Parenchyma ‘‘working tissue’’
- Stroma ‘‘scaffold and nutrition’’
What are the types of tissue and their role?
- Connective: protects and supports eg.fat, blood, cartilage
- Epithelial: covers/lines body surfaces
- Muscle: cells contract to generate force
- Nervous: generate electrical signals in response to environment
How are cells joined together in tissues?
Anchored to each other and other structures by cell junctions.
What is an organ?
Made up of several tissue types comprised in a morphologically recognisable structure.
An organ performs a specific set of functions.
In what steps are tissues processed for histology?
- Fixation
- Embedding
- Sectioning
- Staining
Describe the fixation step?
Can be done by freezing (by dry ice or liquid nitrogen) or by chemical fixation (aldehyde based is most common). This step preserves the tissue.
Describe the embedding step?
This step provides support for the tissue when sectioning. Done by using frozen samples or paraffin wax.
The sample is dehydrated in this step.
Describe the sectioning step?
The thinner the slice, the higher the resolution, a microtome is used to cut thin sections.
A section is a 2D representation of a 3D object.
Describe the staining step?
Most cells are colourless and transparetn and so need to be coloured by stains to view them. The stain can be specific or non-specific.
The cell is rehydrated to stain it.
During staining lipids are dissolved.
What is the most common stain used?
Haemotoxylin and Eosin
Contains 2 dyes (one basic and one acidic)
Describe the haemotoxylin and eosin stain?
Haemotoxylin is basic and so stains acidic structures a purplish blue eg.nucleus.
Eosin is acidic and so stains basic structures red or pink eg. cytoplasm.
What is an other type of stain and what is it used for?
PAS (periodic acid/schiff)- for staining complex carbohydrates and glycogen.
What are the types of epithelia?
-Covering Epithelia; lines/covers body surfaces, cavities, tubes
-Glandular Epithelia; secretory epithelium arranged into glands, also glandular organs
Exocrine glands; retain continuity with surface; secrete via duct
Endocrine glands; lose contact with surface, secrete directly into bloodstream
