ELECTRON MICROSCOPY EPITHELIAL TISSUE SLIDES 22112020 Azhin Saber

ELECTRON MICROSCOPY (EPITHELIAL TISSUE SLIDES) 22/11/2020 Azhin Saber Ali Chnar Hussam Taha MSc in Histology Azhin. saber@tiu. edu. iq BA in Biology chnar. hussam@tiu. edu. iq Lab 5 / Histology and Histopathology (Practical) Tishk International University Science Faculty Medical Analysis Department

Electron microscopy Electron Microscopy can be defined as a specialized field of science that employs the electron microscope as a tool and uses a beam of electrons to form an image of a specimen. An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. 2

Sample preparation for EM • • • Sample size (1 mm) Fixation (gluteraldehyde) Rinse (sodium cacodylate) Post-fixation (osmium tetroxide) Dehydration (alcohol or acetone) Clearing agent (propylene Oxide) Embedding media (various plastics) Sectioning (via ultra microtome) Section thickness (60 -90 nm) Stain (heavy metals) 3

Types of EM 1) Transmission Electron Microscope (TEM); TEMs are typically used for viewing internal features that are inside or beyond the surface (e. g. organelles, macromolecules, atoms). 2) Scanning Electron Microscope (SEM); SEM focuses on the sample’s surface and its composition and shows the sample bit by bit though scanning. 4

Aspect or Feature TEM Classification of electrons Transmitted e- beam (e-) used SEM Scattered (backscattered or secondary) e- Focus of analysis Internal or beyond surface (e. g. Surface of sample (e. g. fine viruses, organelles, atoms, hairs, eye of a housefly) macromolecules) Image presentation 2 -D 3 -D Magnification Up to 50 million magnification level Up to 2 million magnification level Resolution 0. 5 ångströms 0. 4 nanometers Image Color Black and white Cost/maintenance of instrument Very expensive to buy and maintain 5