Atlas of plant and animal histology

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El optical microscope is an essential element for general histology studies since it is that we can observe the different morphological characteristics of cells and tissues. It is based on the use of lenses to increase the rays of light that pass through a tissue sample. Its invention dates back to the 17th century. Since then it has been refined to modern microscopes. For further info, click here: best dissecting microscope

During these centuries, the greatest advance in terms of perfection and quality has been in its main element, the lenses , which increase the image of the tissue sections and allow to make clear details visible to the human eye that would otherwise be impossible to observe. .

Los optical microscopes have a maximum resolution of 0.2 .mu.m . The resolution power is the minimum distance at which two points can be discriminated. This limit is determined by the wavelength of the lighting source, in this case visible light.

It normally contains two lens systems: the objective and the eyepiece. The objective collects the light that passes through the tissue section, while the eyepiece is the one that projects the image onto the retina. The total increasethat an optical microscope allows is calculated by multiplying the magnification produced by the objective by that produced by the eyepiece. For example, if we are using a 40x objective (increases 40 times) and a 10x eyepiece (increases 10 times), the final result will be 400x, that is, we see the sample increased 400 times.

MODIFICATIONS

Contrast phase . This modification of the bright field microscope requires special objectives and is based on the slight delay that light undergoes when it passes through tissue structures depending on its density . In this way different luminosities are achieved for different tissue structures. It is used to view unstained or aqueous samples, as well as live cells, for example in cell cultures.

 Campo dark . Darkfield observation is a good substitute for phase contrast for observing unstained specimens or aqueous media. It consists of the incorporation of an opaque object under the condenser , between the light source and the tissue section. This object only lets in the most lateral light that will strike the sample obliquely and only that light that is reflected by the sample will reach the targets.

Interference interference and Nomarski . This type of microscopy appears only in the most advanced microscopes and involves having special objectives . These methods give the tissues a three-dimensional appearance , that is, they increase the depth of field (thickness of tissue that is simultaneously focused, that is, that is seen clearly). 

It is based on the use of filters that polarize light , which consists in allowing only electromagnetic waves that vibrate in a certain plane to pass. Later they pass through a prismwhich regroups this light into elements separated by a distance that is similar to the resolving power of the target being used. There is a prism for each objective.

VARIANTES

Stereomicroscope . Also called a dissecting microscope, a binocular loupe, or simply a magnifying glass. It is normally used to manipulate small samples or to observe characteristics that do not require large magnifications, between 7 and 40 X of magnifications, although they can go up to 100x. Samples can be observed at different magnifications, which is achieved by using a zoom system or exchanging targets.

FLUORESCENCE

Fluorescence microscope is used to view fluorescent substances called fluorophores . A fluorescent molecule is one that is capable of capturing electromagnetic radiation with a certain wavelength and emitting other electromagnetic radiation with a different wavelength, usually within the spectrum of visible light. 

Fluorophores are used as markers for the detection of other tissue molecules, usually by the immunofluorescence technique. Those used in microscopy absorb in the range of ultraviolet light, normally produced by a mercury lamp, and emit in the range of visible light.



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