Histo by limchu

• Histology


  Branch of biology that studies the microscopic anatomy of biological tissue; it is the microscopic counterpart to gross anatomy
• Tissue


  A group of cells that usually have common point of embryonic origin, and function together
• Embryonic germ layers from which epithelial tissue is derived

  • Ectoderm
  • Mesoderm
  • Endoderm
• Epithelial tissue


  • Highly cellular, composed of cells that closely packed together with very minimal intervening intercellular substances
  • Avascular (without vessels)
• Epithelial tissue classification based on morphology

  • Squamous
  • Cuboidal
  • Columnar
• Epithelial tissue classification based on stratification

  • Simple
  • Stratified
  • Pseudo-stratified
  • Transitional
• Muscle tissue


  Basic type of tissue that enables locomotion and movement due to high contractility
• Types of muscle tissue

  • Skeletal
  • Cardiac
  • Smooth
• Muscle tissue is derived from mesoderm (except for iris of eye – ectoderm derived)
• Myogenesis


  Process of muscle formation or production during embryonic development
• Characteristics of muscle tissue types

  • Skeletal
  • Cardiac
  • Smooth
• Nervous tissue


  Consist of both nerve cells (neurons) and neuroglial cells (supporting cells)
• Nervous tissue is derived from ectoderm
• Parts of a neuron

  • Cell body (perikaryon)
  • Axon
  • Dendrite
• Connective tissue


  Derived from mesoderm, abundant, low amount of cells scattered apart and not bound to each other
• Types of connective tissue

  • Connective tissue proper
  • Special type of connective tissue (cartilage, bone, blood)
• Pathology


  Study (logos) of disease (pathos, suffering); involves the investigation of the causes of disease and the associated changes at the levels of cells, tissues and organs. It provides the scientific foundation for the practice of medicine
• Etiology


  Origin of a disease, underlying causes and modifying factors
• Pathogenesis


  Refers to the steps in the development of disease. It describes how etiologic factors trigger cellular and molecular changes that give rise to the specific functional and structural abnormalities
• Pathologists identify changes in the gross (macroscopic) or microscopic appearance (morphology) of cells and tissues and biochemical alterations in body fluids
• Principal adaptive responses of cells

  • Hypertrophy
  • Hyperplasia
  • Atrophy
  • Metaplasia
• Cell injury


  Develops when the adaptive capacity of the cell is exceeded or if the external stress is inherently harmful. When the stress is severe, persistent and rapid in onset, it results in irreversible injury and death
• Types of cell death

  • Necrosis
  • Apoptosis
• Cellular adaptation to stress

  Reversible changes in the number, size, phenotype, metabolic activity, or functions of cells in response to changes in their environment
• Types of cellular adaptation

  • Physiologic adaptation
  • Pathologic adaptation
• Hypertrophy


  Increase in the size of cells resulting in increase in the size of the organ. In contrast with hyperplasia (increase in cell number)
• Hypertrophy


  • Enlargement of uterus during pregnancy
  • Cardiac enlargement with hypertension or aortic valve disease
• Hyperplasia


  Increase in the number of cells, may occur concurrently with hypertrophy and often in response to the same stimuli
• Types of hyperplasia


  • Physiologic hyperplasia (hormonal, compensatory)
  • Pathologic hyperplasia
• Hyperplastic process is a regulated process, if the signal that initiate it abate, the hyperplasia disappears. It is the responsiveness to normal regulatory control mechanism that distinguishes pathologic hyperplasia from cancer
• Atrophy


  Shrinkage in the size of cell by the loss of cell substance. When a significant number of cells are involved, the entire tissue or organ diminishes in size, becoming atrophic
• Causes of atrophy


  • Decreased workload
  • Loss of innervation
  • Diminished blood supply
  • Inadequate nutrition
  • Loss of endocrine stimulation
  • Aging (senile atrophy)
• Metaplasia


  Reversible change in which one adult cell type (epithelial or mesenchymal) is replaced by another adult cell type
• Metaplasia


  • Squamous change in respiratory epithelium of habitual cigarette smokers
  • Squamous metaplasia of respiratory epithelium often coexist with lung cancers
• Reversible cell injury


  In early stages or mild forms of injury, the functional and morphologic changes are reversible if the damaging stimuli is remove
• Types of cell death

  • Cell death (pathologic) - necrosis
  • Apoptosis (physiologic)
• Features of necrosis and apoptosis

  • Cell size
  • Nucleus
  • Plasma membrane
  • Cellular contents
  • Adjacent inflammation
• Reversible cell injury


  Morphological changes that can be reversed if the damaging stimuli is removed
• Cell death


  Irreversible injury where the cell cannot recover and dies
• Types of cell death

  • Necrosis (pathologic)
  • Apoptosis (physiologic)