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Histological Techniques - What is histology?

  • What is Histology?
  • Histology History
  • Histology Staining
  • Histology Table of contents

So what is histology?. The definition of Histology is the study of anatomy of animals and plants down to the cellular level. This involves analysis of biological tissue using microscopy to look at specimens carefully prepared using special processes called "histological techniques".

It is performed by first using process called fixation of the tissue using a suitable fixative, mostly 10% neutral buffered formalin. Then the tissue then undergoes processing, mainly to paraffin wax. After this it is Embedding, again mainly into paraffin wax to form a block. Then the tissue block is sectioned using Microtomy. This allows examinination of a thin slice of tissue, which picked up on a slide is stained using normally a Haematoxylin and eosin stain so it can be examined under a light microscope or if you need to examine further into the tissue you can go as far as using an electron microscope which is covered more fully under Electron microscopy. The ability to visualize or differentially identify microscopic structures is frequently enhanced through the use of histological stains also known as special stains or immunohistochemistry or immunofluorescence. Sometimes if a diagnosis is urgent a Frozen section can be performed, often used in hospitals in operations for thyroid or ureter identification.

The Biomedical scientists who carry out the procedures, require high level of training to be competent in all the procedures, only possible after completion of a Registration portfolio. Later on further developement to specialise in this area requires completion of a specialist portfolio or the full name specialist portfolio in cellular pathology.

The discipline of histology began in 1665 after Robert Hooke an English microscopist discovered the existence of the cell while examining a piece of cork with a rudimentary microscope. After this the study of cells lead to further medical and scientific breakthroughs.

In the 19th century, the 1906 Nobel Prise in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal. They had dueling interpretations of the neural structure of the brain based in differing interpretations of the same images. Cajal won the prize for his correct theory and Golgi for the staining technique he invented to make it possible which later became known as the golgi stain.

Since then the number of stains used in the laboratory has increased enormously from then most common haematoxylin and eosin to other more specialised or special stains ranging from the mucin detection stain alcian blue to the Tuberculosis or TB detection stain of Ziehl Nielson or ZN stain. These special stains result in improved histology diagnosis enormously in hospitals across the world.

The main staining procedures in the laboratory can be divided into Amyloid detection, useful for amyloidosis diagnosis, Bacterial like gram for distinguish between gram + and -, Groccott for fungi, connective tissue like van gieson, Carbohydrates and mucins using Alcian Blue Periodic acid Schriff stain, Fibrin staining using Martius Scarlet Blue, Lipids using Oil Red O and also pigment and mineral stains like Reticulin for fibres and Perl Prussian Blue for Iron.