Stages of inflammatory response: first stage

STAGES OF INFLAMMATORY RESPONSE

First Stage: Vascullar and Cellular Response

At the start of the first stage of inflammation, blood vessels at the site of injury constrict followed by dilation of small blood vessels. Thus, more blood flows to the injured area. This marked increase in blood supply is referred to as hyperemia and is responsible for the characteristics sign of redness and heat.

Vascular permeability increases at the site with dilation of the vessels in response to cell death, the release of chemical mediators and the release of histamine. Fluids, proteins and leukocytes leak into the insterstitial spaces, and the sign of inflammation swelling and pain appear. Pain is caused by the pressure of accumulating fluid on the nerve endings.

Blood flow slows in the dilated vessels. allowing more leukocytes to arrive at the injured tissues. leukocytes line up along the inner surface of the blood vessels- a process called margination,

then move through the blood vessel wall into the affected tissue spaces , a process called emigration. Leukocytosis happens in response to the exit of leukocytes from the blood.