Introduction to pathology- Lecture 1

Introduction to pathology :

Types of microscope:

1- Light microscope:
It’s a device used for magnifying the objects to give more dilates and to give opportunity to examine the tiny things that invisible by necked eye.
The magnification power of light microscope is (40 – 1000) times.
Parts of the light microscope:
• eye piece (two eye pieces = binocular microscope) (X-10-5-2)
• Revolving nose piece, that hold the objective lenses.
• Objective lenses.(X 4-10-40-and 100, oil emersion).
• Mechanical stage, that hold the slide and enable the examiner to move the slide forward, backward, left and right.
• Light condenser, that concentrate the light beam from the light source on the slide (condenser contain a converging lens).
• Light source .
• Filter and diaphragm, available to manage the quality and intensity of the light .
• Coarse adjustment.
• Fine adjustment.
• Body and base.
2- Fluorescent microscope:
It a special type of microscopes, used in specific fields of diagnosis and mainly used in study of diseases of immunity, in this type of microscope we use a special fluorescent dye to stain the tissue and not the ordinary H&E stain.
3- Electron microscope:
This type of microscope used to give a high magnifying powers (more than 1000 times) , and its of two types:
• Emission electron microscope.
• Scanning electron microscope.
Types of specimens:
1- Biopsy from living tissue:
• incisional biopsy (part from the mass or the lesion).
• Excisional biopsy (removal all the lesion or organ).
2- Autopsy:
Specimens taken by the forensic doctor from the cadaver (after death), to know the cause of death and its of great importance from legal point of view.

Methods of slide preparation:
All specimens derived to the histopathology department must be adequately identified , so for each specimen we have to receive the following informations:
( patient name, age, sex, type of operation, referring doctor and department , and any clinical suggestions).
Then for each specimen we give a serial numbered and this number recorded in the lab. records.
The number identifies the specimen throughout all further slide preparation procedures .
The purpose of the tissue preparation and processing is the preservation of cellular structures and details and to obtain a transparent section can be examined by the pathologist to reach to the particular diagnosis.
Types of microtomes:
1- Rotary microtome, which is the most common type used in all histopathological Lab. Cut the paraffin block in thickness ( 3-5 ) micron. The rotary microtome composed from the following parts:
• The base of the device.
• The body which contain the mechanical parts.
• The block holder that hold the paraffin block.
• Knife holder that hold the stainless steel knife in front of the paraffin block.
• Micron s – adjustment that control the thickness of cutting, and it could be mechanical or digital.
• Fly wheel , and this part will move the paraffin block up and down and bring the knife closer to the block with each round from the fly wheel, this fly wheel can rotate manually of by motor.
2- Freezing microtome (cryostat), which depend On freezing of the fresh tissue in low temperature, and then cut the tissue in thickness ( 10-20 ) micron.
3- Ultra-microtome, repair ultra-thin section for Electron microscopy.