Histopath part 1

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

  • Histology
  • Histopathology
• Epithelial tissue


  These cells have strong adhesion and form cellular sheets that cover surface of the body and line its cavities
• Types of Epithelial Tissue

  • Simple (one layer)
  • Pseudostratified
  • Stratified
• Cell Forms in Epithelial Tissue

  • Squamous
  • Cuboidal
  • Columnar
  • Transitional
• Examples of Epithelial Tissue Distribution

  • Lining of blood vessels (endothelium)
  • Serous lining of cavities; pericardium, pleura, peritoneum (mesothelium)
  • Alveoli of the lungs
  • Portions of the kidney tubules
  • Covering of the ovary, thyroid, kidney tubules, glands and their ducts, choroid plexuses of the brain, lung the terminal bronchioles of the lungs
  • Lining of the intestine, gallbladder, bronchioles of the lungs, auditory tubes, uterus, uterine tubes, stomach, bile ducts, ventricles of the brain, glands and some ducts
• Main Functions of Epithelial Tissue

  • Covering and Secretion
  • Protection, lubrication, absorption, secretion
  • Facilitates the movement of the viscera (mesothelium), active transport by pinocytosis (mesothelium and endothelium), secretion of biologically active molecules (mesothelium)
  • Protection, secretion; cilia-mediated transport of particles trapped in mucus out of the air passages
  • Protection against abrasion; prevents water loss
  • Protection, secretion, prevents water loss
  • Protection and secretion
  • Protection and distensibility
• Connective tissue


  Functions in a mechanical role, they provide a matrix that connects and binds the cells and organs and ultimately gives support to the body
• Fibroblast


  Cells that synthesize collagen, elastin, glycosaminoglycans, proteoglycans and multi adhesive proteins
• Collagen


  The most abundant protein in the human body. Collagen contains 2 amino acids that are characteristic of this protein: hydroxyproline and hydroxylysine
• Examples of Collagen Stains

  • Van Gieson's stain
  • Masson's Trichrome stain
  • Mallory's Aniline Blue stain
  • Azocarmine stain
  • Krajian's Aniline Blue stain
• Reticular fibers


  Consists mainly of collagen type III. They are not visible in hematoxylin-and-eosin (H&E) preparations but can be easily stained BLACK by impregnation with silver salts. Because of their affinity for silver salts, these fibers are called ARGYROPHILIC
• Reticular fibers are also Periodic Acid-Schiff (PAS)-positive. PAS also stains reticulin purplish red. Both PAS positivity and argyrophilia are considered to be due to the high content of sugar chains associated with these fibers
• Stains for Reticular Fibers

  • Gomori's Silver Impregnation Stain for Reticulin
  • Reticulin Stain Gordon and Sweets' Method
• Fibrillin


  A family of proteins related to the scaffolding necessary to the deposition of elastin
• Marfan Syndrome


  Mutations in the fibrillin gene result in Marfan Syndrome, a disease characterized by a lack of resistance in the tissues rich in elastic fibers. Because the large arteries are rich in components of the elastic system and because the blood pressure is high in the aorta, patients with this disease often experience aortic rupture, a life-threatening condition
• Ehrler-Danlos Syndrome


  A group of diseases characterized by defects in collagen synthesis or structure. Because the abnormal collagen fibers lack adequate tensile strength, the skin is hyperextensible and joints are hypermobile
• Amyloidosis


  Caused by the deposition of extracellular proteins with the predilection for forming insoluble β-pleated sheets
• Stains for Amyloid


  • Gram's Iodine Stain
  • Congo Red method
  • Krajian's Amyloid Stain (Modified Bennhold Method)
  • High pH Congo Red Technique
  • Metachromatic staining
  • Induced Fluorescent Staining with Thioflavine
  • Methyl violet (crystal violet method)
• Examples of Hyaline Cartilage

  • Walls of the larger respiratory passages (nose, larynx, trachea, bronchi)
  • Ventral ends of ribs
  • Epiphyseal plate
• Examples of Elastic Cartilage

  • Auricle of the ear
  • Walls of the external auditory canals
  • Auditory (eustachian) tubes
  • Epiglottis
  • Cuneiform cartilage of the larynx
• Example of Fibrocartilage: Intervertebral disk
• Types of Muscle Tissue

  • Skeletal Muscle
  • Cardiac Muscle
  • Smooth Muscle
• Skeletal Muscle


  • Very long, cylindrical, MULTINUCLEATED (peripheral), that show CROSS-STRIATIONS
• Cardiac Muscle


  • Elongated, BRANCHED, UNINUCLEATED (central) cells, with CROSS-STRIATIONS
• Smooth Muscle


  • Fusiform cells, SPINDLE-SHAPED, UNINUCLEATED (central), DO NOT SHOW CROSS-STRIATIONS in the light microscope (No Striations)
• Voluntary Control


  Skeletal Muscle
• Involuntary Control


  Cardiac Muscle, Smooth Muscle
• Cardiac muscle has INTERCALATED DISK, a special structure found only in Cardiac muscles
• Helly's Fluid (Zenker-Formol)


  Can be used to fix the intercalated disk found in cardiac muscle
• Nissl Bodies/Nissl substance/Tigroid substance/Chromatoidal substance

  Refers to the basophilic material in the cytoplasm of the neuron. Ultrastructurally, this material can be identified as large aggregates of rough endoplasmic reticulum (rER), with the RNA content providing the basis for demonstration by special light microscopic techniques
• Stains for Central Nervous Tissue

  • Bielschowsky's Technique
  • Bodian's stain
  • Sevier-Munger Technique
  • Cresyl Fast Violet
  • Kluver & Barrera Luxol Fast Blue
  • Weil's method
  • Modified Palmgren's method
• Astrocytes


  Represent the major supporting cells in the brain. They respond to injury by producing a dense network of processes, somewhat analogous to the fibrous scar that occurs elsewhere in the body. However, in contrast to the fibroblast, astrocytes do not produce collagen
• Glial Fibrillary Acid Protein (GFAP)


  Protein produced by Astrocytes, serves as a unique marker for Astrocytes
• Pathology


  Devoted to the study of the structural, biochemical, and functional changes in cells, tissues, and organs that underlie disease
• Rudolf Carl Ludwig Virchow


  Father of Modern Pathology, Father of Cellular Pathology
• Four Aspects of a disease process that form the core of Pathology

  • Etiology (Cause)
  • Pathogenesis
  • Molecular and Morphologic Changes
  • Functional Derangements and Clinical Manifestations
• Hypertrophy


  Increased cell and organ size, often in response to increased workload; induced by growth factors produced in response to mechanical stress or other stimuli; occurs in tissues incapable of cell division
• Hyperplasia


  Increased cell numbers in response to hormones and other growth factors; occurs in tissues whose cells are able to divide or contain abundant tissue stem cells
• Atrophy


  Decreased cell and organ size, resulting from decreased nutrient supply or disuse; associated with decreased synthesis of cellular building blocks and increased breakdown of cellular organelles
• Metaplasia


  Change in phenotype of differentiated cells, often in response to chronic irritation, that makes cells better able to withstand the stress; usually induced by altered differentiation pathway of tissue stem cells; may result in reduced functions or increased propensity for malignant transformation