How Do Wounds Heal?
Research work on acute wounds in an animal model shows that wounds heal in four phases. It is believed that chronic wounds must also go through the same basic phases. Some authors combine the first two phases. The phases of wound healing are:
* Proliferation or Granulation
* Remodeling or Maturation
Once the source of damage to a house has been removed and before work can start, utility workers must come in and cap damaged gas or water lines. So too in wound healing damaged blood vessels must be sealed. In wound healing the platelet is the cell which acts as the utility worker sealing off the damaged blood vessels. The blood vessels themselves constrict in response to injury but this spasm ultimately relaxes. The platelets secrete vasoconstrictive substances to aid in this process but their prime role is to form a stable clot sealing the damaged vessel. Under the influence of ADP (adenosine diphosphate) leaking from damaged tissues the platelets aggregate and adhere to the exposed collagen. They also secrete factors which interact with and stimulate the intrinsic clotting cascade through the production of thrombin, which in turn initiates the formation of fibrin from fibrinogen. The fibrin mesh strengthens the platelet aggregate into a stable hemostatic plug. Finally platelets also secrete cytokines such as platelet-derived growth factor (PDGF), which is recognized as one of the first factors secreted in initiating subsequent steps. Hemostasis occurs within minutes of the initial injury unless there are underlying clotting disorders. Inflammation Phase:
Clinically inflammation, the second stage of wound healing presents as erythema, swelling and warmth often associated with pain, the classic “rubor et tumor cum calore et dolore”. This stage usually lasts up to 4 days post injury. In the wound healing analogy the first job to be done once the utilities are...