Histology Lecture 1 PDF

Lecture: 1 Histology Types of Microscope  “Micro” = very small “Scope” = to look at  Scientists use microscopes to visualize cells that are too small with the naked eye.  Magnification: degree of...

Lecture: 1 Histology Types of Microscope  “Micro” = very small “Scope” = to look at  Scientists use microscopes to visualize cells that are too small with the naked eye.  Magnification: degree of  Resolution: power to show enlargement. details clearly.  N.B: The critical factor in obtaining a good and detailed image with a light microscope is resolving power.  The most important units of measurements used in histology are:  One centimeter (cm) = 10 millimeters (mm).  One millimeter (mm) = 1000 micrometer = 1000(μ).  One micrometer (μm) = 1000 nanometer (nm).  One nanometer (nm) = 10 Angstrom = 10 Ao. Old Microscope By Spider Medicine Page |1 Lecture: 1 Histology Types Of Microscope Light Electron Bright field microscopy ,as well as It is a type of microscope in which more special types all are based a beam of electrons is used to on the interaction of light with describe the fine structures of the tissue components. examined specimen.  Simple Student Optical.  Transmission.  Phase Contrast.  Scanning.  Fluoresence.  Polarizing. CARRY A MICROSCOPE CORRECTLY Carry it with 2 HANDS:  one on the arm.  the other on the base Make sure it’s on a flat surface. By Spider Medicine Page |2 Lecture: 1 Histology Components Of Light Microscope 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 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. By Spider Medicine Page |3 Lecture: 1 Histology 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 By Spider Medicine Page |4  Lecture: 1 Histology Objective Ocular lens: Total lens: magnification: Low power (for observing 4x 10x 40x large area) medium ( for medium 10x 10x 100x magnification High ( for more detailed 40x 10x 400x area) Higher magnification (oil x100 10x x1000 immersion) 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, phasecontrast microscopes are prominent tool in studying living cultured cells. By Spider Medicine Page |5 Lecture: 1 Histology Polarizing Microscope  Study crystals & substances with repeated arranged molecules ex: collagen, microtubules & microfilaments).  features without such structures are not seen. By Spider Medicine Page |6 Lecture: 1 Histology Confocal microscopy  Achieve high resolution and sharpness by using a small high intensity light from a laser.  It Produces specimen with 3D image. Electron Microscope  Used to observe very small objects which is can’t be seen by light microscope.  Uses beams of electrons rather than light. Much more powerful and give greater magnification.  Types of electron microscope: A. Transmission Electron Microscope (TEM). B. Scanning Electron Microscope (SEM). By Spider Medicine Page |7  Lecture: 1 Histology 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 By Spider Medicine Page |8  Lecture: 1 Histology Scanning electron microscopy (SEM).  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 By Spider Medicine Page |9 Lecture: 1 Histology By Spider Medicine P a g e | 10