Histopathology (Histology)

Histopathology, This branch of medical science studies the physiological changes that occur in tissues. And the branch of medical science that deals with the study of tissues is called Histology.


Tissues received in this department are prepared for microscopic examination. This section covers all the steps involved from specimen collection to preparationthe of stained slides for microscopic examination.


A tissue sample obtained during surgery or an operation from a living person is called a biopsy.


A tissue sample obtained during a postmortem to determine the cause of death of a person is called an autopsy.


Stages of Histotechnique:

  • Documentation
  • Fixation
  • Gross Examination
  • Decalcification
  • Tissue Processing
  • Embedding
  • Microtome
  • Sectioning
  • Staining
  • Mounting

Introduction of Histotechnique Stages:

Following are the steps from receiving the specimen in the laboratory to preparing the stained slide.


Each sample is assigned a specific number. This growth is also written on the slip that comes with the sample and on the sample box.


In this stage, the cells are preserved in their original physical and chemical state to prevent tissue transformation and destruction in the subsequent stages. Chemicals used for this purpose. Their fixative is called 10% Formalin.

Gross Examination:

At this stage, the sample received is visually inspected. Its size is noted by color. If the biopsy is small, it is processed in its entirety; if the biopsy size is large, that particular part is selected.


If the recipient tissue is too hard, the main reason is the accumulation of calcium salts in the tissue, eg bones. Calcium is first extracted from such a tissue sample. So that the sample becomes soft and can be cut easily.

Tissue Processing:

The process itself consists of three steps which are as follows:

  • Dehydration
  • Dealcoholization / Clearing
  • Impregnation

In Tissue Processing, the entire biopsy received or a selected portion of the biopsy is solidified by passing it through the above three steps so that thin tissue sections can be easily obtained.


In this stage, after tissue processing, the sample is placed in a specific mold and given a specific shape so that sections can be easily obtained. This specially shaped sample is called a tissue block.



In this process, the NATO block is made by using a specific type of machine table (Section). This machine is called Microtome. The sections made by microtomes are very thin, their thickness is of micron level. Light can easily pass through these sections and they can be well inspected.


A microtome section is picked up on a slide. And it is stained under a specific method. So that different parts of the tissue can be distinguished during microscopic examination.


In this step, a cover slip is placed over the tissue section on the slide. So that the tissue section is preserved forever.

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