Circulatory System & Inflammatory Response

Circulatory System & Inflammatory Response

Circulatory System & Inflammatory Response

The inflammatory response

Inflammation is a non-specific immune response to trauma, endogenous antigens, chemical agents and microbial pathogens. The inflammatory response occurs immediately after trauma and prevents pathogenic proliferation, minimises further damage to cells and tissue and finally enhances repair and healing. Inflammation manifests itself by redness, swelling, heat and pain, together with alteration of function . The processes involved in inflammation may be summarised as:

mobilisation of resident macrophages

localised vasodilation

increase in vascular permeability

infiltration of area by leukocytes

damage repair -clotting process

Principle events in the inflammatory response are shown schematically in Fig. 01

The redness and heat observed in inflammation are caused by vasodilation bringing blood to the area of injury. Swelling is oedema resulting from increased vascular permeability, allowing plasma into the interstitial area. Swelling may also result in pain due to localised pressure stimulating pain receptors.

Mast cells are found in connective tissue adjacent to blood vessels. In response to trauma, chemical agents or triggering by the immune system, they release mediators (locally acting chemicals). These can be preformed in granules and released very quickly in a process termed degranulation. Alternatively, they can be synthesised de-novo by the mast cell and released over a longer period, Figure 02.

Fig. 02. The role of the mast cell in inflammation

The mast cell releases mediators in response to injury or stimulation by the immune system, IgE antibodies and complement proteins (Porth 2007).

Products of degranulation include histamine which causes vasodilation and increased permeability of blood vessels. Chemotactic factors are also released in degranulation which attract neutrophils (early response leucocytes) and monocytes (late response leukocytes) both of which mature into phagocytes.

Vascular permeability

Under the influence of mediators such as histamine, small blood vessels dilate and become more permeable. Plasma is exuded from the blood into the interstitial ...