WEEK 1: Intro to Histology

• HISTOLOGY


  study of the tissues of the body and how these tissues are arranged to constitute organs
• HISTOPATHOLOGY


  refers to the study of the tissue in order to study the manifestation of the disease
• HISTOTECHNOLOGY


  field of science that involves processing of tissue to be able to study them under the microscope
• CELLS AND EXTRACELLULAR MATRIX


  tissues have two interacting components:
• ECM


  supports the cells and contains the fluid transporting nutrients to the cells, and carrying away their wastes and secretory products
• HISTOLOGIC SECTIONS

  thin, flat slices of fixed and stained tissues or organs mounted on glass slides
• LONGITUDINAL


  plane of section that cuts in the midline
• TRANSVERSE


  plane that intersects the longitudinal axis at right angle
• TANGENTIAL


  graze or only pass through the outermost periphery
• OBLIQUE


  neither longitudinal or transverse (slanting medj parang eggplant na slices)
• FIXATION


  small pieces of tissue are placed in solutions that cross-link proteins and inactivate degradative enzymes, which preserves cell and tissue structure
• DEHYDRATION


  tissue is transferred through a series of increasingly concentrated alcohol solutions, ending in 100% which removes all water
• CLEARING


  alcohol is removed in organic solvents in which both alcohol and paraffin are miscible
• INFILTRATION


  tissue is placed in melted paraffin until it becomes completely infiltrated with this substance
• EMBEDDING


  paraffin-infiltrated tissue is placed in a small mold with melted paraffin and allowed to harden
• TRIMMING


  paraffin block is trimmed to expose the tissue for sectioning (slicing) on a microtome
• SECTIONING


  uses a device called microtome and can cut tissues into sections 1 to 10 micrometers thick
• MOUNTING


  thin sections are mounted upon glass slides
• STAINING


  process that permit distinctions of tissue components (colors)
• HEMATOXYLIN


  - basic dye

  - stains acidic parts of cells

  - gives off blue color

  - stains nucleus and rough endoplasmic reticulum
• EOSIN


  - acidic dye

  - stains the basic parts of cells

  - gives off pink color

  - stains the cytoplasm, mitochondria, and lysosome
• MASSON'S TRICHROME STAIN


  - nuclei stain black or blue black

  - muscles stain red

  - collagen and mucus stain green or blue

  - cytoplasm of most cells stain pink
• PERIODIC ACID-SCHIFF REACTION


  glycogen stains deep red or magenta
• VERHOEFF'S STAIN FOR ELASTIC TISSUE


  - Elastic fibers stain jet black

  - Nuclei stain gray

  - Remaining structures stain pink
• MALLORY-AZAN STAIN


  - erythrocytes stain red-orange

  - cytoplasm of liver and kidney stains pink

  - nuclei stain red

  - fibrous connective tissue, mucus, and hyaline cartilage stain deep blue
• WRIGHT'S OR GIESMA'S STAIN


  - erythrocyte cytoplasm stains pink

  - lymphocyte nuclei stain dark purple-blue with pale blue cytoplasm

  - neutrophil nuclei stain dark blue

  - eosinophil nuclei stain dark blue and the granules stain bright pink

  - monocyte cytoplasm stains pale blue and nucleus stains medium blue
• CAJAL'S AND DEL RIO HORTEGO'S METHODS (SILVER AND GOLD METHODS)


  - myelinated and unmyelinated fibers and neurofibrils stain blue-black

  - general background is nearly colorless

  - astrocytes stain black

  - depending on the methods used, the end product can stain black, brown, or gold
• OSMIC ACID (OSMIUM TETROXIDE) STAIN


  - lipids in general stain black

  - lipids in myelin sheath of nerves stain black
• BRIGHT-FIELD MICROSCOPE


  - ordinary light

  - microscope: optical system

  - mechanism: move and focus the specimen
• VIRTUAL MICROSCOPY


  - typically used for study of bright field microscopic preparations

  - conversion of a stained tissue preparation to high-resolution images

  - computer and other digital device without an actual stained slide or a microscope
• FLUORESCENCE MICROSCOPY


  - irradiated with ultraviolet light

  - emission is in the visible portion of the spectrum

  - fluorescent substances appear bright on a dark background
• PHASE-CONTRAST MICROSCOPY


  - lens system that produces visible images from transparent objects

  - living cultured cells

  - unstained transparent and colorless
• DIFFERENTIAL INTERFERENCE MICROSCOPY


  - modification of phase-contrast microscopy

  - Nomarski optics: living cells 3d aspect
• CONFOCAL MICROSCOPY


  - high resolution and sharp focus

  - small point of high-intensity light (laser)

  - plate with pinhole aperture in front of the image detector

  - computer-driven mirror system (beam splitter) for automatic and rapid movement of point of illumination
• POLARIZING MICROSCOPY


  - allows recognition of stained or unstained structures made of highly organized subunits

  - appear as bright structures against a dark background
• TRANSMISSION AND SCANNING ELECTRON MICROSCOPES


  - based on the interaction of tissue components with beams of electrons

  - wavelength of electron beam is much shorter than that of light, allowing a 1000-fold increase in resolution
• TRANSMISSION ELECTRON MICROSCOPES


  basic principles of operation: a beam of electrons focused using electromagnetic "lenses" passes through the tissue section to produce an image with black, white, and intermediate shades of gray regions.
• SCANNING ELECTRON MICROSCOPY


  provides a high resolution view of the surfaces of cells, tissues, and organs. Like the TEM, this microscope produces and focuses a very narrow beam of electrons, but in this instrument the beam does not pass through the specimen.
• EYEPIECE (OCULAR LENS)


  Magnifies the primary image formed by the objective lens.
• NOSEPIECE (REVOLVING TURRET)


  Designed to hold objective lenses permitting changes of magnification by rotating different powered objective lenses into optical path.