Healing of any injured or damaged tissue is brought about by migration of blood cells towards this are with the help of increased localised blood flow. Platelets reach the injured tissue through this mechanism and are responsible for clotting or coagulation of blood cells or help in minimising blood loss due to the injury. In addition, platelets also release Growth Factors, which are an essential part of the healing process. Platelets are composed of an alpha granule and a dense granule which contain a number of proteins and growth factors. On activation due to injury, the platelets undergo alteration in shape and develop branches to spread over injured tissue to help stop the bleeding in a process called aggregation, followed by the release of growth factors, mainly from the alpha granules.
These growth factors thus give impetus to the healing process and its three stages namely
The growth factors derived from the platelets set the inflammatory stage in motion. This is marked by the appearance of monocytes, as they are quick to respond to inflammatory trigger and help in mounting an immune response. Growth factor production is at its highest level immediately following the inflammatory stage. Fibroblasts can be seen to enter the site of injury within 48 hours and become the most abundantly available cells by Day 7. The fibroblasts start depositing collagen (building block of tissues) for many weeks afterwards. Maturation of Collagen is a long phenomenon and may continue for 1-2 years following the initial insult. It is vital to know the stages are a chain reaction with one stage stimulating the next. There would be no collagen deposition by fibroblast if it is not preceded by an inflammatory stage. An insignificant immune response would be insufficient in bringing about regeneration of injured and tissues and make the injured tissue prone for degenerative changes to set in.