Acute inflammation

• What is the model of pathogenesis of periodontitis?

  
• What does acute mean?

  A response which is abrupt in onset and short duration
• What are the main features of acute inflammation response?

  1. rubor - redness

  2. tumor - swelling

  3. calor - warmth

  4. dolor - pain

  5. functio laesa - loss of function

  The suffix "itis" is used to denote an inflammatory lesion e.g. pulpitis, periodontitis
• What are causes of acute inflammation?

  Any agent which causes cell damage

  a) Physical agents – Trauma e.g. mechanical injury, such as cutting and crushing, heat, cold and ionising radiation

  b) Chemical agents – e.g. corrosive acids and alkalis

  c) Deprivation of blood supply

  d) Living organisms – infection

  e) Antigen-antibody reaction – Damage caused by immune complexes
• What is the vascular response?

   Hyperaemia - more blood and appears red

   Initial constriction of blood vessels followed by a period of prolonged vasodilatation

   Blood flow brings warmer arterial blood to surface (calor)

   Initially blood flows to veins through central channels

   Precapillary sphincters open - blood passes into capillary bed

   Shut down vessels become functional

  
• What changes in the blood flow during inflammation?

  • In acutely inflamed tissue, speed of the blood increases at first but soon diminishes
  • Blood stasis follows
  • Clear zone occupied by numerous white blood cells 'Margination' of white blood cells
  • Endothelium 'pavemented' by white blood cells
  • Characteristic of acute inflammation: due to changed vascular endothelium - cells become swollen and sticky Gaps appear through which fluid and plasma protein can move

  
• What is blood flow like in healthy tissue?

   Blood flow in arterioles of normal tissue : very fast individual cells cannot be identified

   In venules, slower flow, still difficult to identify individual cells

   Cells travel in central zone of blood vessel : leave a clear, cell free zone adjacent to endothelium
• What is emigration of white cells?

  White cells strike the endothelium by chance Pseudopodia push between adjacent endothelial cells, penetrate the basement membrane and emerge on the external surface of the venule
• What are the major events of the local inflammatory response?

  • chemical signals released by macrophages (when activated) and mast cells at injury site, nearby capillaries widen and become more permeable
  • fluid, antimicrobial proteins and clotting elements move from blood to site and clotting begins
  • chemokines attract more phagocytic cells from the blood to the injury site
  • neutrophills and macrophages phagocytose pathogens and cell debris at site and tissue heals

  
• What is the inflammatory exudate?

   Collection of fluid in the extravascular tissues and consists of:◦ The fluid exudate ◦ The cellular exudate
• What is the fluid exudate?

  Formed by increased permeability of the vessels wall to plasma proteins There are several categories of exudates, depending on the amount of proteins and/or cells that leave the vessels

  
• What is serious exudate?

  ◦ This is associated with mild inflammation◦ Clear fluid with a relatively low protein content and very few cells e.g. fluid in a blister
• What is Fibrinous exudate?

  ◦ Rich in protein, particularly fibrinogen When it enters the tissue, exudate clots due to the formation of fibrin ,e.g. pleurisy of the lung in bacterial pneumonia
• What is Suppurative exudate?

  Is rich in neutrophils and is recognised clinically as pus

  
• What is the function of the fluid exudate?

  All plasma constituents pour into area - natural antibacterial substances (like complement) as well as specific antibodies Drugs and antibiotics may also be present Exudate dilutes irritant substance
• What is Fibrinogen?

  clotting protein in blood
• What is Fibrin?

  an insoluble protein formed from fibrinogen during the clotting of blood. It forms a fibrous mesh that impedes the flow of blood.
• What are the three main functions of Fibrin?

  1. It forms a union between severed tissues 2. It may form a barrier against bacterial invasion3. It aids phagocytosis
• What is the cellular exudate?

  • Cells accumulate in the extravascular space
  • PMNs, some monocytes
  • Within a few days PMNs necrose but monocytes remain
  • Cells are attracted by chemotaxis
  • Attracted by bacteria and antigen-antibody complexes
• what are PMN's/neutrophils/leukocytes?

  A type of white blood cell
• What is the function of cellular exudate?

  Phagocytosis: Polymorphonuclear leucocytes

  
• What is Opsonisation?

  The coating of a pathogen with antibodies to promote and enhance phagocytosis
• What is phagocytosis aided by?

  Opsonisation  Opsonins are proteins present in plasma which coat organisms and cause them to be more easily phagocytosed

   Cover up noxious surface antigens

   Non-specific opsonins

   Immune opsonins: antibacterial antibody (specific)

   Phagocytosis is more marked where immunisation against the organism has occurred
• What is Surface Phagocytosis?

  Phagocytes work better with a framework to trap the organisms. Fibrin promotes surface phagocytosis. PMNs which have ingested particles show degranulation. Digestive lysosomal enzymes of the granules are poured into the vesicle
• What are Macrophages?

  Infection-fighting organisms in lymph, derived from blood monocytes, Highly phagocytic and help initiate immune response
• What is pus caused by?

  • Pyogenic (pus forming) bacteria e.g streptococci, staphylococci, pneumococci, meningococci andgonococci
  • Encourage emigration of neutrophils (PMN) which then die
  • Pyogenic organisms have antiphagocytic capsule
  • Neutrophils continue to accumulate (purulent exudate= pus)
  • Neutrophils and tissue die (liquefactive necrosis)
• What is an Abscess?

  A collection of pus in a pyogenic membrane Creamy pus is typical of staphylococcal infections where fibrin is abundant in the pus Streptococci secrete proteases and fibrinolysins, which digest fibrin and other fibrous proteins - results in thin pus

  
• What are the constituents of pus?

  1. White blood cells (leucocytes) – living and dead

  2. Other components of the inflammatory exudate – oedema fluid and fibrin

  3. Organisms – living and dead

  4. Tissue debris – e.g. lipids and nucleic acids
• What is a sinus?

  Sinus = epithelial lined tract along which the pus travels to the surface
• What is a fistula?

  Fistula = pus drains to another body cavity
• What happens in an abscess cannot drain?

  walls of the abscess become covered into dense fibrous tissue pus thickens (like porridge) and becomes calcified
• How is an ulcer formed?

  When an acute suppurative inflammation involves an epithelial surface, the covering is destroyed and an ulcer is formed
• What is an ulcer?

  A localised defect of a covering or lining epithelium