histo methods

• Histology


  The study of the microscopic anatomy of tissues which involves the examination and architectural description of the microscopic anatomy of normal cells of the body and all their contents and products

  
• Histology is performed by examining a thin slice (section) of tissue under a microscope
• Why we study histology

  • Understanding the normal structure and function of different tissues is essential for interpreting the changes that occur during disease
  • To develop a mental image of the microscopic appearance of cells, structures, tissues, and organs
  • To correlate microscopic appearance with function in health and disease
  • To provide a basis for later study of anatomy and pathology
  • Because it's awesome

  
• Where does histology fit in?

  • Anatomy
  • Biochemistry
  • Physiology
  • Microbiology
  • Pathology
  • Pharmacology
  • Gross Anatomy
  • Embryology
  • Microscopic Anatomy/Histology
  • Radiological Anatomy
  • Surface Anatomy

  
• Cell theory


  The scientific theory that all living organisms are made of cells as the smallest functional unit
• Innovations in science arise when ideas and theories that are popular at the time are combined with new technological methods
• Histological Hierarchy - Structural organization of the body


  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organism
• Cell


  The smallest basic structure and function of higher organisms capable of independent existence
• Cytology


  The study of cells
• Structural components of a cell

  • Organelles - metabolically active
  • Cytoskeleton - structural framework (fibrillar elements)
  • Inclusions - cell products, metabolites (metabolically inactive)
  • Cytosol - fluid component (cytoplasmic matrix, intracellular fluid)
• Tissue


  A group of cells along with extracellular ground substance, of similar function and origin that form functional units
• Four basic types of human tissue

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Organ


  Composed of various tissues, have special shape, structure and function
• Components of an organ

  • Parenchyma (the cells that perform the main function of organ)
  • Stroma (supporting tissue)

  
• Organ system


  Composed of several organs which have related function
• Organism


  Formed of different levels of organization, with increasing levels of complexity and each of which plays important roles in the physiological homeostasis of the body
• Microscopic study of tissue is called Histology

  
• Types of Histology


  • General Histology - Microscopic study of the 4 basic tissues
  • Systemic Histology - Microscopic study of tissues of the different organs/organ systems

  
• Sources of tissue for histological examination

  • Biopsy - examination of tissue taken from a living body
  • Autopsy - examination of post-mortem tissue
  • Necropsy - examination of tissue taken from dead animal
• Basic sample preparation techniques prior to histological analysis

  • Fixing
  • Processing - dehydration, clearing, and infiltration
  • Embedding
  • Sectioning
  • Mounting
  • Staining
• Special Techniques Used for Histological Diagnosis


  • Light microscopy
  • Electron microscopy
  • Histochemistry
  • Immunohistochemistry
  • Tissue / Cell Culture
  • Cytogenetics and Molecular Cytogenetics
  • Bone Marrow smear / Blood Smear
  • Fine needle aspiration / biopsy
  • Flow cytometry
  • Autoradiography

  
• Histochemistry


  The science of using chemical reactions between laboratory chemicals and components within tissue to give information on the presence and location of intracellular and extracellular macromolecules

  
• Immunohistochemistry


  A highly specific interaction between macromolecules, that between an antigen and its antibody, used to detect and locate specific proteins in tissue sections

  
• Every immunohistochemical technique requires an antibody against the protein or other antigen that is to be detected

  
• Antibodies normally bind specifically to their provoking antigens and help eliminate them

  
• Immunohistochemistry techniques


  • Antibodies tagged with fluorescent compounds
  • Antibodies tagged with peroxidase or alkaline phosphatase for histochemical detection
  • Antibodies tagged with electron-dense gold particles for TEM

  
• Medical application of immunohistochemistry - cells in some diseases, including many cancer cells, often produce proteins unique to their pathologic condition, immunohistochemistry can be used by pathologists to diagnose many diseases, including certain types of tumors and some virus-infected cells

  
• Tissue / Cell Culture


  Live cells and tissues can be maintained and studied outside the body
• Hybridization techniques


  Specific binding between two single strands of nucleic acid, which occurs under appropriate conditions if the strands are complementary
• Hybridization at stringent conditions allows the specific identification of sequences in genes or RNA, which can occur with cellular DNA or RNA when nucleic acid sequences in solution are applied directly to prepared cells and tissue sections, a procedure called in situ hybridization
• Bone Marrow Smear

  Aspiration of the marrow has been primarily utilized for cytologic assessment, with analysis directed toward assessing the morphology and obtaining a differential cell count
• Blood Smear/ Peripheral blood film

  A laboratory work-up that involves cytology of peripheral blood cells smeared on a slide, exposing the morphology of peripheral blood cells

  
• Platforms to detect ALK positive cells

  • Fluorescence in situ Hybridization (FISH)
  • Immunohistochemistry (IHC)
  • Polymerase Chain Reaction (RT PCR)
  • Next Generation Sequencing (NGS)