Cytology · MU Sofia

1. Microscopy. Types of microscopes.

Explains how microscopy lets students see structures beyond the naked eye, then contrasts light microscopes with electron microscopes, including their resolving power and magnification limits. It goes through bright-field, fluorescence, phase-contrast, confocal and polarizing light microscopy, and gives a mnemonic, "Big Friendly Pandas Can Play", to recall them. It also covers transmission and scanning electron microscopy, autoradiography and X-ray crystallography, closing with a summary of how to choose a method.

Inside: 3 sections · 5 labelled pictures · 13 flashcards · 5 min

Topic 1 of 97 in the MU Sofia syllabus for Cytology (Medicine, Year 1). The free AceMed note covers it in 3 sections, about 695 words (5 min of reading), with 13 flashcards.

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Microscopy. Types of microscopes.
Other Methods
Summary of Key Points

Microscopy. Types of microscopes.

Microscopy is a technique used to visualize small objects or structures that are not visible to the naked eye. The sources describe two main types of microscopes: light microscopes and electron microscopes.

Light Microscopy :

Light microscopes use light to illuminate the specimen, and they have a resolving power of 0.2um. This means that objects smaller than this cannot be distinguished, such as ribosomes or membranes, and if two objects are closer than this they cannot be seen as separate.
The basic light microscope uses light that passes through the object, which is then magnified by the objective and eyepiece lenses.

There are several types of light microscopes, including:
Bright-field microscopy: This method uses ordinary light to view stained preparations. The microscope includes an optical system and mechanisms to move and focus the specimen as you can see in the previous image . The optical components include a condenser, objective lens and eyepiece or ocular lens.
Fluorescence microscopy: Some cellular substances emit light with a longer wavelength when irradiated by light of a proper wavelength. This is called fluorescence. This type of microscopy uses fluorescent dyes that bind to specific cellular components, making them more visible. Some dyes, such as DAPI and Hoechst, bind specifically to DNA and are used to stain cell nuclei. Antibodies labeled with fluorescent compounds are also used in immunohistologic staining.

Phase-contrast microscopy: This method does not require the object to be dyed as it measures the time taken for light to pass through the object. This allows for the viewing of living cells. A variation of this method, known as differential interference microscopy, creates a more 3D version of the image.

Confocal microscopy: This technique uses a sharp, focused light, such as a laser, to illuminate the object. The images are then stitched together on a computer, reducing light exposure to the sample and producing a clearer image. Confocal microscopy uses a point of high-intensity light, and a plate with a pinhole aperture to improve resolution and allow the localization of specimen components with precision.

Polarizing microscopy: Polarized light is used, meaning light vibrates in only one direction. This makes macromolecules located between the light source and the lens visible. It allows recognition of structures made of highly organized subunits.

To help remember the types of light microscopes, you can use the mnemonic "Big Friendly Pandas Can Play":

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