Histology - The Very Basics Trivia Quiz

Answer: The microscopic study of animal or plant tissues

Histology is the study of animal or plant tissues microscopically by way of cutting and staining thin sections of tissue for examination.
The study of individual cells is called cytology.
Body fluids are a bit more difficult. There are several different disciplines that can be useful in the study of a body fluid. In a body fluid can be found malignant cells (cytology), white cells and micro-organisms (microbiology and haematology) and various solutes and suspended particles such as electrolytes and albumin, respectively (biochemistry). Phew.

Answer: neutral buffered formalin

Formaldehyde solution is diluted to 10% formalin with a phosphate buffer added to keep the pH neutral. Buffering is required to reduce an artifact in tissues that are kept in formalin for a long time. Formalin pigment is generally a brown discolouration around blood vessels and red cells, and can obscure tissue detail. Another description for it would be "gungy".

Answer: gelatine

Histology has it all. There are physical hazards: from the knives to the lifting of large drums of chemicals. There are chemical hazards: virtually all of the stains used (based on benzene) and fixatives (well, they do kill tissue) are either toxic or hazardous. Last but not least are the biological hazards: you never know where that tissue has been.

Answer: a microtome

The very first version of a microtome was a straight razor. The specimen was held in one hand with the razor in the other. Cutting sections this way took a considerable amount of experience to get right. The average thickness of sections was 20 - 25 micrometres.
A micropyle is a small opening in the surface of the ovule through which pollen passes.
A microscope is an instrument that magnifies objects so that details invisible to the naked eye can be seen.
A microphyte is a microscopic plant. (Not a small worshipper).

Answer: the textile industry

In the nineteenth century, there was a lot of work done with synthetic dyes for textiles. Prior to this, all dyes used in textiles and the biological sciences were derived from natural sources.
There are still a few natural dyes in use today, but their cost is prohibitive.
The most common is haematoxylin (from the tropical logwood tree Haematoxylin camphechiarium). This is the most commonly used dye in histology in conjunction with the synthetic dye eosin (first created in 1850's).
Histology is very old.

Answer: Haematoxylin and eosin

Haematoxylin stains nuclei blue and eosin stains the cytoplasm and fibres of the tissue a pink/red or orange/red. The difference in eosin colours depends on the formulation of the stain.

Answer: light microscopy

Stained tissues are examined using light microscopy with a microscope set up for Kohler illumination.
Dark field is used for spirochaetes, polarising light for birefringence of crystals (usually in joint fluids) and phase contrast is eminently useful for examining bacteria and cells(particularly white cells) in wet preparations and cell counts of fluids.

Answer: they cannot be used for fatty tissues

Mordants enhance binding of dyes to tissues and can be applied either before or during the staining step. They are generally polyvalent metal cations such as Al3+, Fe3+ or Cr3+. Usually the mordant forms a combination of covalent and van der Waals bonds between the stain and tissue, giving stronger dye binding. Of course they can be used on fatty tissues.

Answer: Safranine

Safranine, a dark red stain, is commonly used for wood sections on its own. It is also used with Fast Green to show differences between structures such as lignin and cellulose fibres.

Answer: Always wear protective equipment (gloves, gown, goggles)

When handling anything hazardous, protective equipment must be worn. The only exception would be latex gloves when handling solvents such as xylene. Xylene melts latex, so nitrile gloves should be worn in that case.