HUMAN HISTOLOGY INTRO

• histology

  -study of the tissues of the body and how these tissues are arranged to constitute organs.

  -involves all aspects of tissue biology, with the focus on how cells' structure and arrangement optimize functions specific to each organ.

  -two interacting components: cells and extracellular matrix (ECM).
• AUTOPSY

  dead
• BIOPSY

  alive
• Acidic structures + basic dye = basophilic (e.g. nucleus)
• Basic structures + acidic dye = acidophilic (e.g cytoplasm)
• Bright-Field Microscopy

  -stained preparations are examined by means of ordinary light that passes through the specimen.
• Resolving power

  → defined as the smallest distance between two particles at which they can be seen as separate objects.

  → 0.2 нт
• Fluorescence Microscopy

  -Tissue sections are usually radiated with ultraviolet (Uv) light and the emission is in the visible portion of the spectrum.

  -The fluorescent substances appear brilliant on a dark background.
• Fluorescence

  → Phenomenon wherein certain cellular substances are irradiated by light of a proper wavelength, they emit light with a longer wavelength.

  -bright on dark background

  -does not age well (1 year)
• Phase-Contrast Microscopy

  -based on the principle that light changes its speed when passing through cellular and extracellular structures with different refractive indices.

  -uses a lens system that produces visible images from transparent objects

  -enables examination of unstained cells and tissues and is especially useful for living cells.

  -visualize actual processes
• • interference microscope
  • differential interference microscope

  Phase-contrast microscopy (2)
• Interference microscope

  → allows quantification of tissue mass
• differential interference microscope

  → using Nomarski optics

  → useful for assessing surface properties of cells and other biologic objects.
• Dark-field microscopy

  -no direct light from the light source is gathered by the objective lens.

  -only light that has been scattered or diffracted by structures in the specimen reaches the objective.

  -equipped with a special condenser that illuminates the specimen with strong, oblique light.

  -field of view appears as a dark background on which small particles in the specimen that reflect some light into the objective appear bright.

  -bent
• Confocal microscopy

  • combines components of a light optical microscope with a scanning system to dissect à specimen optically.
  • Uses (1) a small point of high-intensity light, often from a laser, and (2) a plate with a pinhole aperture in front of the image detector.
  • point light source, the focal point of the lens, and the detector’s pinpoint aperture are all optically conjugated or aligned to each other in the focal plane (confocal), and unfocused light does not pass through the pinhole.
  • increase contrast
  • (e.g. disecting a specimen)
• Polarizing Microscopy

  -uses the fact that highly ordered molecules or arrays of molecules can rotate the angle of the plane of polarized light.
• Birefringence

  -ability to rotate the direction of vibration of polarized light

  -common to crystals and active filaments

  -repetitive structures
• Electron Microscopy

  • based on the interaction of tissue components with beams of electrons.
  • The wavelength in the electron beam is much shorter than that of light, allowing a 1000-fold increase in resolution.
  • higher resolution; lower wavelength
• • transmission electron microscope (TEM)
  • scanning electron microscope (SEM)

  2 kinds of electron microscopy
• Scanning Electron Microscopy

  • the electron beam does not pass through the specimen but is scanned across its surface.
  • the surface of the specimen is first dried and spray-coated with a very thin layer of heavy metal (often gold) through which electrons dó not pass readily.
  • When the beam is scanned from point to point across the specimen, it interacts with the metal atoms and produces reflected l electrons or secondary electrons emitted from the

  metal
• Transmission Electron Microscopy

  -an imaging system that permits resolution around 3 nm.

  -magnifications of up to 400,000 times to be viewed in detail

  -uses the interaction of a beam of electrons with a specimen to produce an image.
• Cryofracture and freeze etching

  -a special method of sample preparation for transmission electron microscopy

  → it is especially important in the study of membranes.
• Enzyme Histochemistry

  -a method for localizing cellular structures using a specific enzymatic activity present in those structures.
• Immunohistochemistry

  -A highly specific interaction between molecules is that between an antigen

  and its antibody
• Hybridization Techniques

  -a method of localizing messenger RNA (mRNA) or DNA by hybridizing the sequence of interest to a complementary strand of a nucleotide probe.
• In situ hybridization

  → binding of the nucleotide probe to the DNA or RNA sequence of interest is performed within cells or tissues, such as cultured cells or whole embryos.
• • Bright-Field Microscopy
  • Fluorescence Microscopy
  • Phase-Contrast Microscopy
  • Dark-field Microscopy
  • Confocal Microscopy
  • Polarizing Microscopy

  LIGHT MICROSCOPY (6)
• PREPARATION OF TISSUES FOR STUDY

  A) fixation

  B) dehydration

  C) clearing

  D) infiltration

  E) embedding

  
• The Microtome

  A) drive wheel

  B) block holder

  C) paraffin block

  D) tissue

  E) steel knife

  
• Identify what type of light microscopy

  A) Brightfield

  
• Identify what type of light microscopy

  A) Phase-contrast

  
• Identify what type of light microscopy

  A) Darkfield