Cells and Tissues Flashcards
How does a light microscope work
It uses light refraction by a magnifying lens to create a virtual image that is larger then the actual object.
Magnification = how much the object is enlarged
Resolution is the ability to distinguish between two closely spaced objects.
how do we stain dead cells for viewing and how are they cut
The tissue is made rigid by fixing in formalin and embedding tissue is paraffin wax. It can also be frozen in a block
A microtome is used to cut 1-10micrometer sections
How can we look at living cells
Can be viewed using H&E stains or immunohistochemistry(enzyme labelled or fluorescent antibodies).
Can use phase contrast or differential interference to view living cells
Explain Phase contrast
Phase contrast microscopy exploits the phase differences in the light waves that pass through different parts of a specimen. Transparent structures, which may otherwise be difficult to observe, can be visualized because they alter the phase of the light passing through them. In the resulting image, structures with different refractive indices appear with varying degrees of brightness and darkness, enhancing the visibility of cellular details without the need for staining.
Explain differential interference
DIC creates contrast by utilizing the interference of polarized light. It separates a beam of light into two mutually perpendicular polarized beams, which are then recombined after passing through the specimen. The resulting interference pattern creates contrast in the image. DIC microscopy produces images with a 3D appearance, enhancing the visualization of fine details, edges, and surface topography. The specimen appears as if it is casting shadows, providing a pseudo-three-dimensional effect.
Explain fluorescence microscopy
A type of microscopy which is used to identify different structure within a cell by illuminating them using fluorescent tags.
The process begins with the labeling of specific structures or molecules within a specimen with fluorescent dyes or proteins. These fluorophores absorb light at one wavelength (excitation wavelength) and emit light at a longer wavelength (emission wavelength).
The specimen is illuminated with light of the excitation wavelength, which is specific to the fluorophores used. This light excites the fluorophores, causing them to absorb energy and move to higher energy states
After absorbing energy, the fluorophores return to their lower energy states by emitting light at the emission wavelength which is different to the absorbed wave length. This emitted light is what produces the fluorescence. This is what is captured by a camera or another detector to produce an image.
What is confocal microscopy and why is it better than fluorescence
it uses lasers as a source of light and also uses pinholes. produces a higher resolution image because it reduces background noise and eliminated out of focus light. NOT UNDERSTOOD
What is transmission electron microscopy
a type of microscopy which uses electrons to create an image of the specimen.
EMs use an electron gun to generate a beam of electrons. This beam is accelerated by an electric field, creating a high-energy electron source
The electron beam passes through a series of condenser lenses and an aperture to focus and shape the beam before it reaches the specimen
Specimens for TEM must be extremely thin, typically on the order of 50 to 100 nanometers. Common specimen types include ultrathin sections of biological tissues, cells, or nanomaterials. This thinning process is often achieved using a microtome.
As the electron beam passes through the specimen, it interacts with the electrons in the sample. The dense regions of the specimen absorb more electrons, resulting in variations in electron density.
The transmitted electrons pass through the specimen and interact with a fluorescent screen or a detector on the other side. The resulting image is formed by the differences in electron transmission, providing a detailed representation of the specimen’s internal structures.
What is scanning electron microscopy
Scanning Electron Microscopy (SEM) is a technique that uses a focused electron beam to scan the surface of a specimen. As the beam interacts with the specimen, signals such as secondary electrons and backscattered electrons are generated. These signals provide information about the specimen’s topography and composition. SEM is particularly useful for producing high-resolution, three-dimensional images of the surface of materials and biological specimens. It is widely applied in various scientific fields for detailed characterization and analysis at the nanoscale.
Name specialised EM methods
- Shadowing
- Freeze-fracture and freeze-etch
- Negative staining
- Cyroelectron microscopy
- Image enhancement.
what are the 5 types of basic tissue
Blood
Connective tissue
Epithelial tissue
muscle tissue
nervous tissue
What are the components of blood
Plasma - proteins + inorganic salts and water
Cells - RBC, WBC platelets
Functions of connective tissue
Provides structure + metabolic support
Contains blood vessels
Contains tissue defence mechanisms
Important in tissue repair.
3 types - loose, dense and specialised
Functions of dense connective tissue + example
To provide physical support - Tendon
Functions of loose connective tissue + example
Packing between cells and tissues - dermis + adipose
