The Basics of Acute Inflammation

Acute Appendicitis by Euthman

Inflammation, described in the simplest terms is the local physiological response to tissue injury.

Many things can cause this ‘injury’, from microbial infections (bacteria, viruses, etc) through to physical agents (e.g. trauma, heat, etc).The primary goal of inflammation is to bring phagocytes and plasma proteins to the area such that they can destroy the invaders, remove debris and prepare for subsequent healing.

Inflammation is often categorised firstly by its time course; Acute & Chronic Inflammation. Acute inflammation consists of the initial response of the body to tissue injury, whilst chronic inflammation is the prolonged tissue reactions following the initial response. Today I shall focus on the former.

There are Five Cardinal Signs of Acute Inflammation which occur due to a number of reasons.
  • Rubor (redness): Dilatation of small blood vessels in damaged area
  • Calor (heat): Increased blood flow to area (hyperaemia)
  • Tumour (swelling): Accumulation of fluid in extracellular space (edema, British: Oedema)
  • Dolor (pain): Stretching/distortion of tissue from oedema (esp. from pus), chemical mediators can induce pain
  • Loss of function: Movement hindered etc.
Below is pictorially summary (albeit messy) of some of the basic elements of the Acute Inflammation process.

For a larger image click on the one above.

Edit 28/2/11: New graphical representation of Acute Inflammation process.


Chemical mediators of inflammation interact with other immune cells to elicit an appropriate response (in autocrine/paracrine fashion, an occasionally through the blood). For a full list of chemical mediators, click here.

It is important to remember that there are both good and bad aspects to acute inflammation.
The Good.
  • Dilution of toxins
  • Entry of antibodies
  • Transport of drugs
  • Fibrin formation (traps microbes, serves as a matrix for granulation tissue)
  • Delivery of nutrients & oxygen
  • Stimulation of immune response
The Bad.
  • Swelling (can occlude airways, raise intra-cranial pressure and so on)
  • Inappropriate inflammatory response.
  • Digestion of normal tissues
The interplay between Acute & Chronic Inflammation

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