A very comprehensive and accurate summary of the histology of the different types of epithelium [including glandular epithelium] and connective tissue for first year histology. Easy to follow, simple, yet comprehensive summary.
What is histology?
Histology is the study of microscopic biological material.
Includes the structure and function of tissue (as the knowledge of normal structure and function is
needed to ID diseased tissue + make diagnostic tools and to develop tissue/ cell substitutes and
replacement tissue)
Why do we study histology?
Nowadays we do microsurgery instead of normal surgery
We have moved from organ transplants to cell transplants/replacements (e.g. Stem Cells)
We need to create a good environment for cells to grow in
We can develop new technologies for diagnosis of disease
Where does tissue come from?
1. Normal tissue:
o Cosmetic surgery (breast, skin)
o Amputations (bone, skin, muscles)- rare
o Body donations
o Alternative animal tissues (primates [eye esp.] and pigs [skin esp.])
2. Pathologic tissue:
o Diagnostics biopsies (colon, breast etc.)
o Surgical removal of tissue (liver, colon, breast, etc.)
‼ BUT ethics of acquiring tissues: ‼
o Human- informed consent from patient/ guardian
o Animal- animal ethics committee
Techniques used in histology:
1. Tissue processing:
Fix tissue (freeze tissue in space and time)
Tissue is dehydrated and the water is replaced paraffin wax
This ensures a degree of hardening so the section can be cut without ‘squashing’ cells
Cells cut with a microtome into sections ≈5μm thick
Placed on glass slide
Paraffin wax removed
Tissue stained
2. Staining Methods:
General staining methods:
, Haematoxylin and Eosin (H&E) Staining:
Haemotoxylin: Eosin:
Stains: DNA and RNA Cytoplasm
Colour: Purple/dark blue Pink
Type: Basophilic Acidophilic
Dye association: Positive metals (Al3+) Negative charge
Dye binding: Negatively-charged Positive amino acids (Arg, lys)
components of cell (staining floating in the cytoplasm
conditions optimized so that it
doesn’t bind with protein)
Most common method
Cells with high metabolic rate have high levels of RNA in cytoplasm (to make protein for more
structures) – meaning that the cytoplasm will be predominantly blue.
Silver and gold methods:
Used for looking at neurons
May-Grunwald-Giemsa method:
Used for identification of different bloodcell types
Immunocytochemistry (ICC):
Used for localisation of specific proteins
Normal immune response:
o Body recognises proteins on surface and antibodies (Ab) attach to antigens (Ag)
Same method used to identify other proteins
o A commercial Ab binds to a specific region of a protein Ag
o Binding cannot be seen so a detection system is required; colorimetric + fluorimetric
Colorimetric: Fluorimetric:
Most commonly used Less commonly used
Enzyme (Horseradish Peryoxidase [HRP]) Fluorescent dye bound to a primary or
bound to a secondary Ab secondary Ab
Substrate: DAB Detection direct
Colour of product: brown Wide range of colours
Won’t be tested
on these
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