Microscopes Lecture 1 PDF

 Lecture 1 DR. Presented by Dr Doaa Khaled, Lecturer of Histology , school of medicine , Helwan University  Objectives at the end of this lecture you should be able to 1- Recognize some terminology 2- Describe Light microscope:...

 Lecture 1 DR. Presented by Dr Doaa Khaled, Lecturer of Histology , school of medicine , Helwan University  Objectives at the end of this lecture you should be able to 1- Recognize some terminology 2- Describe Light microscope: components and handling. 3-Mention special types of light microscopes. 4- Describe electron microscopes (E.M): Types & principles. 5- Compare between LM & EM  Microscopes - Scientists use microscopes to visualize cells that are too small with the naked eye Micro” = very small “Scope” = to look at Magnification: degree of enlargement Resolution: power to show details clearly N.B : The critical factor in obtaining a good and detailed image with a light microscope is resolving power 2 The most important units of measurements used in histology are: 1. One centimeter (cm) = 10 millimeters (mm). 2. One millimeter (mm) = 1000 micrometer = 1000(μ). 3.One micrometer (μm) = 1000 nanometer (nm). 4.One nanometer (nm) = 10 Angstrom = 10 Ao.  What is the resolving power of the micr0scop (its resolution )? It is the smallest distance between two structures at which they be can be seen as separate objects. = 0.2 µm it is the best resolving power which can permit magnification up to 1000-1500. Structures smaller than 0.2 µm ( as ribosomes) can’t be distinguished  OLD MICROSCOPES  Types of microscopes 1)- Light microscopes (LM): Bright field microscopy ,as well as more special types all are based on the interaction of light with tissue components 2)- Electron microscopes (EM): It is a type of microscope in which a beam of electrons is used to describe the fine structures of the examined specimen. CARRY A MICROSCOPE CORRECTLY Carry it with 2 HANDS…one on the arm and the other on the base Make sure it’s on a flat surface Components of light microscopes: 1- The frame ( base, arm and stage) 2- The magnifying system ( lenses system) 3- Illumination system: source of light may be mirror to reflect day light or an electric lamp Light microscope (LM) component  The optical lens system of light microscope 1- Condenser: Present under the stage, Collects and focuses a cone of light that illuminate the tissue slide on the stage. 2- The objective lense: Enlarge and project the illuminated image of the object in the direction of the ocular lens (eye pieces). 3- The ocular lens (eye pieces): Further magnifies this image and projects it onto the viewer’s eye n.b : Objective lenses providing higher magnification &high resolving power. - The eyepiece lens only enlarges the image obtained by the objectives and doesn’t improve resolution What’s my power? To calculate the power of magnification, multiply the power of the ocular lens by the power of the objective. Ocular lense Objectives lenses  Objective Ocular lens Total lens magnification Low power (for 4x 10x 40x observing large area) medium ( for medium 10x 10x 100x magnification High ( for more 40x 10x 400x detailed area) Higher magnification x100 10x x1000 (oil immersion) Which of these images would be viewed at a higher power of magnification? Other specialized types of light microscopes: 1- Phase contrast microscope & Interference microscope. 2- Fluorecence microscope (will be discussed by microbiology depaertment). 3- Polarizing micorscope. 4- Confocal microscope. Phase Contrast Microscopy Study the unstained cells (transparent &colorless). Because they allow the examination of cells without fixation or staining, phase- contrast microscopes are prominent tool in studying living cultured cells. PHASE CONTRAST  Studycrystals & substances with repeated arranged molecules ex: collagen, microtubules & microfilaments).features without such structures are not seen. Tissue apperance with Polarizing microscopy Confocal microscopy Achieve high resolution and sharpness by using a small high intensity light from a laser. It Produces specimen with 3D image.  ELECTRON MICRSCOPY (EM) 2. Electron Microscope Used to observe very small objects which is can’t be seen by light microscop. Uses beams of electrons rather than light. Much more powerful and give greater magnfication Types of electron microscop: A- Transmission Electron Microscope (TEM) B-Scanning Electron Microscope (SEM) 1)-Transmission EM 1- The resolution power around 0.2nm. 2- The magnification power up to 400,000 times. 3- ultrathin sections (40-90nm) are needed. 4- Principles: a beam of electron focused using electromagnetic lenses instead of glass lens used in light micrscope. This electron emitted from heating of tungesten filament (cathod). 5- The final color of image is: black (electron dense) and white (electron lucent) shades.  6- Electron lucent mean that the electrons passed easily through the tissue (sites of electron penetration) -----while electron dense mean the (sites of electron absorption or deflection). 7- To see the final image, a fluorescent screen is needed to convert the energy of electrons into light Scanning electron micro- scopy (SEM). Cilia Preparation: 1- Coating of specimen surface with a heavy metal (gold). 2- When the beam electron exposed to the its surface, some electron are reflected then collected by a detector to form the black & white 3D image showed on tv screen 3- So the image will show the surface of a specimen only , the electron beam doesn't pass through the specimen. E.M Differs from L.M in: 1. An electron beam is used instead of light rays. 2. Electromagnetic coils are used instead of glass lenses. 3. The final image is visualized on a fluorescent screen. References Basic book.Janqueira's Basic Histology.Text and Atlas. 14,15 th edition. Lange Medical Book, McGraw-Hill. Recommended Books: 1- Wheater's Functional Histology. A Text color Atlas Recommended Web Sites. www.histology world.com www.blue histology.com www.visual histology.com Thank you CERTIFICATE OF With my COMPLETION. YOU DID A REALLY best wishes GREAT JOB!