Lecture 1.2: Histology Flashcards
What is histology?
It is the study of the microscopic structure of tissues.
Why is it necessary to preserve fresh tissue? (4)
To prevent putrifaction
To preserve proteins
To maintain structure
To preserve nucleic acids
Why is it difficult to cut thin sections of fresh tissue? How to combat this issue?
Fresh tissue is soft and will lose its integrity as the microtome blade passes through it
Fixation process
Embedding
Cryopreservation
Which methods allow for effective sectioning of tissues?
Cyropreservation (freezing)
Embedding in a solid medium such as wax/ plastic
What is the process of Embedding?
1) The biopsy must first be fixed (e.g. formaldehyde)
2) Ethanol (70-100%) used to dehydrate the biopsy
3) Xylene/ Toluene used for clearing
4) Then the biopsy can be embedded into wax (at 56 degrees Celsius)
On which component of cells to fixatives act?
Proteins generally
Name 3 common fixatives
Alcohol
Formaldehyde
Glutaraldehyde
Most common dehydrating agent?
Alcohol
Most commonly used basic dye? What does it stain?
Haematoxylin (dyes purple)
It stains nucleic acids (DNA, RNA)
Most commonly used acidic dye? What does it stain?
Eosin (dyes pink/red)
It stains proteins
Periodic Acid Schiff (PAS)
Dyes a deep red/magenta
Stains mucin, glycogen, complex carbohydrates and glycoproteins
Which stain is most effective at discriminating connective tissue structure when combines with cross-polar microscopy?
Sirius Red
Which dye most effectively stains connective muscle and tissue?
Masson’s trichrome
Which dye most effectively stains glycoprotiens?
PAS
Which dye(s) most effectively stains general tissue organisation?
Haemotoxylin and Eosin
Which dye(s) most effectively stains different immune cells?
Giemsa (or Wright’s)
Which dye most effectively stains reticular proteins?
Silver Stain
Which dye(s) most effectively stains elastic fibres?
Van Gieson or orcein
What is the study of the identification and distribution of chemical compline’s within and between cells, by means of stains, indicators and microscopy called?
Histochemistry
Reveals structure in unfixed and unstained (often live) sample by exploiting retardation of light as it passes through specimens
Phase contrast microscopy
Detects light emitted by UV-illuminated specimens, allowing identification of specific spotters immunolabelled with dyes such as fluorescein
Fluorescence microscopy
Provides high resolution imaging by passing a high-energy beam of electrons through a very thin section
Transmission Electron Microscope (TEM)
Scattered light from samples illuminated from the side reveals structure in unstained specimens
Dark field
A technique used to reveal collagen organisation in picrosirius stained specimens
Cross-polar microscopy
Routine study of stained sections
Bright-field microscopy
Provides high resolution images of surfaces by passing an electron beam across a sample prepared with heavy metals
Scanning electron microscope
Uses laser illumination and a pinhole to allow capture of optical sections
Confocal microscopy
Exploits interference patterns of refracted light to create an impression of depth in unstained and unfixed specimens
Differential (or Nomarski) interference microscopy
When is a smear biopsy used?
Cervix
Buccal Cavity
When is a curettage biopsy used?
Endometrial lining of uterus
When is a needle biopsy used?
Brain
Breast
Liver
Kidney
Muscle
When is a direct incision biopsy used?
Skin
Mouth
Larynx
When is a endoscopic biopsy used?
Lung
Intestine
Bladder
When is a transvascular biopsy used?
Heart
Liver
Nissl bodies
Using appropriate stains, the RER and free ribosomes appear as basophilic, granular areas called Nissl bodies
These are sites of protein synthesis
Are abundant in large nerve cells such as motor neurones
Chromatolysis
Refers to the disintegration/ dispersal of Nissl bodies following motor neurone injury
Breslow Thickness
Measures depth of melanoma invasion from granular layer of epidermis:
<1mm 95-100%
1-2mm 80-96%
2.1-4mm 60-75%
>4mm 37-50%
