Histology and Micro-techniques

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Questions and Answers

What is the main difference between transmission electron microscopy (TEM) and scanning electron microscopy (SEM)?

TEM analyzes living cells, while SEM analyzes fixed cells.

TEM uses light for illumination while SEM uses an electron beam.

TEM produces colored images, while SEM produces black and white images.

TEM requires thin specimens, whereas SEM provides 3D images. (correct)

What type of microscope would be most suitable for studying living unstained cells?

Scanning electron microscope

Transmission electron microscope

Phase contrast microscope (correct)

Fluorescence microscope

In electron microscopy, what does the term 'electron dense' refer to?

Fluorescent substances that emit light.

Components that absorb more electrons and appear dark. (correct)

Components that appear white under electron illumination.

Areas that scatter little to no electrons.

Which histological staining technique is commonly used?

Hematoxylin and eosin (H&E) staining Signup and view all the answers

What is the purpose of conducting a biopsy in medical diagnosis?

To examine the microscopic structure of a tissue. Signup and view all the answers

What is the primary advantage of rapid histological diagnosis in the operating theatre?

Preservation of lipids and enzymes in tissues. Signup and view all the answers

Which stain is primarily used to visualize carbohydrates?

Periodic acid Schiff’s technique. Signup and view all the answers

In terms of staining, what does 'basophilic' refer to?

Affinities towards basic dyes. Signup and view all the answers

What color does Sudan black stain typically produce?

Black. Signup and view all the answers

What type of microscope is known for achieving magnifications up to 100,000 times?

Transmission electron microscope. Signup and view all the answers

Which staining technique is used to visualize live cells outside the body?

Supravital stain. Signup and view all the answers

What is the primary use of eosin in histological staining?

Staining acidic structures. Signup and view all the answers

Which of the following is not a use of special stains?

Staining chromatin. Signup and view all the answers

What is the primary objective of studying histology?

To understand the structure of cells and tissues Signup and view all the answers

Which of the following is NOT a step in the paraffin technique for histological preparation?

Clearing with water Signup and view all the answers

Which microscopy technique is primarily used in histological analysis?

Light microscopy Signup and view all the answers

What is the purpose of applying a fixative like formalin during the paraffin technique?

To prevent putrefaction and autolysis Signup and view all the answers

In the microtome sectioning process, what is the typical thickness of the sections cut from paraffin blocks?

5 um Signup and view all the answers

Which method of tissue preparation involves directly freezing the specimen?

Freezing technique Signup and view all the answers

What is the outcome of dehydration in ascending grades of alcohol during tissue processing?

Preventing tissue shrinkage Signup and view all the answers

Which component is used to render the tissue transparent in the paraffin technique?

Xylene Signup and view all the answers

Study Notes

Histology

The study of the structure of cells and tissues using a microscope
It is important to correlate structure with function and understand the pathology of diseases

Micro-techniques

Micro-techniques encompass the methods employed in preparing and examining tissue samples for histological analysis.
There are two main techniques for preparing thin sections: Paraffin technique and Freezing technique

Paraffin technique

Routine method for histological preparation
Involves several steps to preserve, dehydrate, clear, and embed the tissue in paraffin wax for sectioning
Steps include:
- Obtaining a sample
- Fixation: using formalin to prevent putrefaction and autolysis
- Dehydration: using ascending grades of alcohol (70%-90%-100%) to avoid tissue shrinkage
- Clearing: using xylene to replace alcohol, render the tissue transparent, and prepare it for paraffin infiltration
- Impregnation: infiltrating the tissue with paraffin wax in an oven
- Embedding in paraffin: placing the impregnated tissue in hard paraffin for block formation
- Sectioning: using a rotary microtome to create thin sections (5um thick)
- Picking the section on a slide

Freezing technique

Quick method used for rapid diagnosis in operating theatres
Preserves lipids and enzymes for histochemistry
Employs cryocut for freezing the specimen

Staining

Used to enhance the visibility of subtle structures in tissue sections

Ordinary histological stain

Hematoxylin and Eosin (H&E)
Hematoxylin stains basic structures (nucleus) blue, and Eosin stains acidic structures (cytoplasm) pink

Special stains

Used to highlight specific components or structures within the tissue
Carbohydrates:
- Periodic acid Schiff’s technique (PAS): stains carbohydrates magenta
- Best's carmine: stains glycogen red
Lipids:
- Frozen sections are used:
  - Sudan III: stains lipids orange
  - Sudan black: stains lipids black
  - Osmic acid: stains lipids black
Vital stain:
- Involves staining living cells in vivo by injecting dyes like Trypan blue, e.g., for phagocytic cells
Supravital stain:
- Involves staining living cells in vitro outside the body, e.g., mitochondria by Janus green B
Metachromatic stain:
- Involves staining with a color different from the color of the dye, e.g., granules of mast cells are stained red when stained with toluidine blue

Microscopy

The microscope is an instrument that magnifies the image and reveals fine details of an object.
Types of microscopes:

Light Microscopy

Magnification: up to 1000 times
Types: Student, Compound, Stereo

Electron Microscopy

Magnification: up to 100,000 times
Types:
- Transmission Electron Microscopy (TEM):
  - Utilizes an electron beam for illumination
  - Creates black-and-white images
  - Dark components are electron-dense, and white components are electron-lucent
  - Requires extremely thin sections (0.08 um)
- Scanning Electron Microscopy (SEM):
  - Provides three-dimensional images of the surface of the specimen

Other types of microscopes

Phase Contrast Microscope: used to study living or fixed unstained cells
Fluorescence Microscope: used to detect fluorescent substances

Case Scenario

A 45-year-old female patient presents with a swelling in her neck
Clinical examination reveals a firm, non-tender, but fully mobile mass
Ultrasound suggests the mass may be malignant
A biopsy is needed for a proper diagnosis

Summary

Histology is the study of the structure of cells and tissues, correlating structure with function and understanding disease pathology.
Micro-techniques for tissue processing include paraffin and freezing techniques.
Common histological stains include H&E, with special stains highlighting specific structures.
Microscopes, including light and electron microscopes, are vital tools for visualizing cellular and tissue details.

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Description

Explore the fascinating world of histology, the study of cell and tissue structures using microscopy. This quiz covers key micro-techniques for preparing tissue samples, focusing on the paraffin method. Test your knowledge on the steps involved in histological preparation and the importance of structure-function correlation.