Inflammation- Definition, causes and its types

Types of Inflammation

Based on intensity and duration of the process inflammation can be classified as:

I. Acute Inflammation

II. Chronic Inflammation

I. Acute Inflammation

Acute inflammation is quick to develop and lasts for a few hours or days and is characterized by a painful red swelling due to the collection of an exudate. The inflammatory cells are mainly neutrophils and the  heals in a short time or may persist and pass on into a chronic inflammation.

acute vs normal

Stimulation for Acute Inflammation

Acute Inflammatory reactions may be triggered by a variety of stimuli:

  • Foreign bodies (splinters, dirt, sutures)
  • Infections (bacterial, viral, parasitic) and microbial toxins
  • Trauma (blunt and penetrating)
  • Physical agents (e.g. thermal injury like burns, frostbite, radiation)
  • Chemical agents
  • Tissue necrosis
  • Immune reactions

Components of Acute Inflammation

i. Vascular Changes

ii. Cellular Changes

 i. Vascular Changes

The main vascular reactions of acute inflammation are increased blood flow and increased vascular permeability, both designed to bring blood cells and proteins to sites of infection or injury. In addition, endothelial cells are activated, resulting in increased adhesion of leukocytes and migration of the leukocytes through the vessel wall. While the initial encounter of an injurious stimulus, such as a microbe, is with macrophages and other cells in the connective tissue, the vascular reactions triggered by these interactions soon follow and dominate the early phase of the response.

Features

  • Local vasodilation of capillaries and venules.
  • Slowing down of blood flow.
  • Changes in flow pattern of cells and plasma-margination of leukocytes.
  • Leukocytes-endothelium interaction.
  • Increased vascular permeability.

ii. Cellular Changes

Cellular changes  involves neutrophils, macrophages, eosinophils, lymphocytes, endothelial cells and platelets as well as the local epithelium and connective tissue elements (extracellular matrix). The leukocytes emigrates from the circulation and accumulates in the focus of injury (cellular recruitment), followed by activation of the leukocytes, enabling them to eliminate the offending agent. The principal leukocytes in acute inflammation are neutrophils (polymorphonuclear leukocytes).

Features

  • Leukocytes migrate out of the capillary due to the phenomenon of chemotaxis and by the process of pseudopodial locomotion.
  • Leukocytes surround the bacteria and contact them.
  • Leukocytes phagocytose the organism
  • Leukocytes initiate lysis of bacteria both inside their cytoplasm (by lysosomes) as well as outside (by oxygen radicals, serum complement antibodies and eicosanoids)
  • The leukocytes, platelets, endothelial cells release a number of cytokines, and growth factors.
  • Both neutrophils and macrophages get to clean up the area of the damage.
Inflammation- Definition, causes and its types

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