Histopathology Notes
Introduction
. Microscopic study of individual cell in a smear is called cytology and study of tissue is called histology.
Histology is a department of anatomy that deals with the minute structure, composition and functions of tissues. Histopathology means the study of diseased tissues.
The pathologist responsible for the diagnosis of diseased tissues is dependent on the technical skill of a histotechnologist, who prepares microscopic slides of the specimen.
These specimen slides should be well
sectioned and properly stained to provide detailed in-formation of the tissue under examination
Histopathological studies have proved to be one of the most effective means in diagnosing tissue abnormalities, benignand malignant conditions.
Exfoliative cytology, is concerned with the early detectionof cancer.
The malignant cells diffuse into the body fluids and secretions (exfoliate). The exfoliative cytological techniques deal with the study of body fluids and secretions by direct smear method and also by the study.
The specimen processing includes the following basic steps..
1Fixing
When a tissue is removed from the body it begins to decompose. To preserve the natural state (asnearly as possible) the tissue is immediately placed into a solution called fixative and this process is called fixing.
2 Embedding
To provide necessary hardness to cut sections,
infiltration of paraffin wax is carried out. This
process is called embedding, which involves
a) Removal of water by alcohol dehydration,
b) Infiltration of xylene or chloroform as a solvent
for paraffin wax and (c) Introduction of wax
impregnation.
3 Microtomy
Thin sections (slices) of the tissue are cut by using an equipment called microtome. This is performed when the paraffin is solidified and the tissues are ready in the form of blocks. These thin sections are then prepared for staining.
4 Staining
The paraffin is removed from the section on the slide by drying and then by dewaxing. During dewaxing the sections on the slide are treated first with xylene and then the sections are rehydrated with ethyl alcohol in decreasing concentrations.The rehydrated sections are then stained by using appropriate staining methods.
5 Mounting
After staining, the sections on the slides are
dehydrated by treating with ethyl alcohol in
increasing concentrations and finally with xylene.By placing mounting medium such as Canada balsam and then by placing a cover slip on the mounting medium, the stained sections on the slide are said to be mounted.
✏Microtomes✏
Microtomes are used for cutting paraffin tissue sections of uniform thickness. This instrument is designed to cut 1 to 60 u thin sections.
The most Important parts of a microtome✏
1. The block holder: In this the tissue is held in
position
2. The knife carrier and the knife.
3. The adjustment screws and rachet device.
These help to line up the tissue in proper
relation to the knife and also provide proper
thickness of tissues for successive sections
Use for various perpose :-
1.➡Embedded tissues are cut by either a rotary
microtome, rocking microtome or by a sliding
microtome. For rotary and rocking microtomes,
paraffin embedding is required while celloidin
embedded sections are cut by a sliding
microtome. A sledge microtome is designed forCutting sections of very
large blocks of tissue. (for example, whole brain).
2➡The freezing microtome and the cold (or cryostat) microtome is used for cutting frozen
section of a tissue. Unembedded soft specimens are generally cut in the frozen state, since frozen condition of the specimen gives the necessary rigidity for cutting the sections. This method is useful for rapid histopathologicaldiagnosis during an operation. It is also an
useful method to examine the sections of a
structure or a substance (e.g. fat) that would
be destroyed in routine preparation of sections.
3.➡In the case of a freezing microtome, the specimen is kept frozen by liquid carbon
dioxide, while the knife of microtome is warm.
The cold microtome, however, is kept in a cold
chamber (20°C) and unlike the freezing
microtome, the knife is also cold.
4 ➡ Ultra microtomes are used to prepare very thin
sections (upto 1 um thickness) which are
examined by using electron microscope.
Introduction
. Microscopic study of individual cell in a smear is called cytology and study of tissue is called histology.
Histology is a department of anatomy that deals with the minute structure, composition and functions of tissues. Histopathology means the study of diseased tissues.
The pathologist responsible for the diagnosis of diseased tissues is dependent on the technical skill of a histotechnologist, who prepares microscopic slides of the specimen.
These specimen slides should be well
sectioned and properly stained to provide detailed in-formation of the tissue under examination
Histopathological studies have proved to be one of the most effective means in diagnosing tissue abnormalities, benignand malignant conditions.
Exfoliative cytology, is concerned with the early detectionof cancer.
The malignant cells diffuse into the body fluids and secretions (exfoliate). The exfoliative cytological techniques deal with the study of body fluids and secretions by direct smear method and also by the study.
The specimen processing includes the following basic steps..
1Fixing
When a tissue is removed from the body it begins to decompose. To preserve the natural state (asnearly as possible) the tissue is immediately placed into a solution called fixative and this process is called fixing.
2 Embedding
To provide necessary hardness to cut sections,
infiltration of paraffin wax is carried out. This
process is called embedding, which involves
a) Removal of water by alcohol dehydration,
b) Infiltration of xylene or chloroform as a solvent
for paraffin wax and (c) Introduction of wax
impregnation.
3 Microtomy
Thin sections (slices) of the tissue are cut by using an equipment called microtome. This is performed when the paraffin is solidified and the tissues are ready in the form of blocks. These thin sections are then prepared for staining.
4 Staining
The paraffin is removed from the section on the slide by drying and then by dewaxing. During dewaxing the sections on the slide are treated first with xylene and then the sections are rehydrated with ethyl alcohol in decreasing concentrations.The rehydrated sections are then stained by using appropriate staining methods.
5 Mounting
After staining, the sections on the slides are
dehydrated by treating with ethyl alcohol in
increasing concentrations and finally with xylene.By placing mounting medium such as Canada balsam and then by placing a cover slip on the mounting medium, the stained sections on the slide are said to be mounted.
✏Microtomes✏
Microtomes are used for cutting paraffin tissue sections of uniform thickness. This instrument is designed to cut 1 to 60 u thin sections.
The most Important parts of a microtome✏
1. The block holder: In this the tissue is held in
position
2. The knife carrier and the knife.
3. The adjustment screws and rachet device.
These help to line up the tissue in proper
relation to the knife and also provide proper
thickness of tissues for successive sections
Use for various perpose :-
1.➡Embedded tissues are cut by either a rotary
microtome, rocking microtome or by a sliding
microtome. For rotary and rocking microtomes,
paraffin embedding is required while celloidin
embedded sections are cut by a sliding
microtome. A sledge microtome is designed forCutting sections of very
large blocks of tissue. (for example, whole brain).
2➡The freezing microtome and the cold (or cryostat) microtome is used for cutting frozen
section of a tissue. Unembedded soft specimens are generally cut in the frozen state, since frozen condition of the specimen gives the necessary rigidity for cutting the sections. This method is useful for rapid histopathologicaldiagnosis during an operation. It is also an
useful method to examine the sections of a
structure or a substance (e.g. fat) that would
be destroyed in routine preparation of sections.
3.➡In the case of a freezing microtome, the specimen is kept frozen by liquid carbon
dioxide, while the knife of microtome is warm.
The cold microtome, however, is kept in a cold
chamber (20°C) and unlike the freezing
microtome, the knife is also cold.
4 ➡ Ultra microtomes are used to prepare very thin
sections (upto 1 um thickness) which are
examined by using electron microscope.
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