CHARACTERISTICS OF THE INFLAMMATORY RESPONSE
– Regardless of the etiological factor, the inflammatory process has three essential components: alteration (tissue damage), exudation (release of fluid and blood cells from vessels into tissues and organs), and proliferation (multiplication of cellular elements).
– The extent and duration of the injury determine the degree and duration of the inflammatory response. The inflammatory response can be localized – and limited to the area of injury, or systemic (generalized) if the damage is extensive.
– The inflammatory response is classified as acute or chronic based on the speed of the process. Microscopic changes occur in the damaged tissues in both acute and chronic inflammation. These changes cause symptoms which can be observable in clinical practice.
– Local clinical changes in the site of inflammation are known as cardinal signs of inflammation: redness, heat, swelling, pain, and loss of normal tissue function. In more extensive responses, systemic signs of inflammation may also be present (such as fever, intoxication, leukocytosis, etc.).
– Vascular response. Microscopic manifestations of inflammation involve small blood vessels, (or the microcirculatory bed). It includes arterioles, capillaries, and venules in the area of injury, as well as red blood cells, white blood cells, and chemical substances known as biochemical mediators. Under normal conditions, blood and its cellular components flow through the microcirculatory bed. Oxygen and nutrient exchange necessary for the health of surrounding tissues occurs as plasma fluid passes between the endothelium lining the walls of arterioles and capillaries. Plasma is the liquid component of blood, consisting mainly of water and proteins, in which blood cells are suspended. Normally, most of the plasma that passes out of the microcirculatory bed returns to the bloodstream through venules. Lymphatic vessels, in turn, remove excess plasma that does not reenter the blood vessel. These processes are disordered resulting the development of inflammation.
– Ischemia. Initially, a brief reflex constriction of blood vessels occurs in the area of injury.
– Arteriovenous hyperemia. Dilation of the same small blood vessels is then observed for several seconds. Dilation is an increase in the diameter of vessels, caused by biochemical mediators released at the moment of injury. The expansion of the microcirculatory bed vessels leads to an enhancement of blood flow through them. The enhanced blood flow filling the capillary bed in the damaged tissue is known as hyperemia. Hyperemia contributes to the appearance of two clinical signs of inflammation: erythema and heat. Erythema, or redness, is easily noticeable in most inflamed tissues of the oral and facial area, while localized temperature changes are more difficult to detect.
