Wounds: the healing process
Ongoing research is opening up our understanding of wound healing and the pathogenesis of the mechanisms of chronic versus acute wound healing. Wound healing is a complex series of interrelated events which combine to return the damaged tissue to as near normal function as possible. It follows a specific sequence of phases which may overlap. The process of wound healing depends on the type of tissue which has been damaged and the nature of the tissue disruption. Deep open wounds in bone do not heal in the same way, or at the same rate, as superficial epithelial wounds, largely because bone “tissue” consists of up to 65 per cent inorganic, calcium-based matrix.
This article describes the wound healing process and outlines some of the cellular and acellular factors involved.
The objective of any wound management regimen is to heal the wound in the shortest time possible and with minimum pain, discomfort and scarring to the patient. Success in fulfilling the objective will be assisted by an understanding of the healing process and a knowledge of the contributions that the existing range of wound management products can make to initiating and maintaining the optimal microenvironment for healing.
Structure of the skin
The skin is the largest organ of the body and its function is protective. It is composed of several layers: the outer epidermis and stratum corneum which protects against injury and contamination, the dermis which contains the capillary network providing nutrients and removing waste, the sensors for detecting pain and immediate environmental changes, and the subcutis from which the dermis and epidermis develop. The skin covers the other organs and, as well as the roles already mentioned, it plays a part in temperature regulation, detection of external pressure and external temperature changes, absorbs sunlight (thus aiding in its conversion to vitamin D) and acts as a waterproof barrier.
The thickness of the epidermal layer varies from a thin membrane at internal flexures, eg, at the elbow, to thick, compacted layers at points which bear considerable pressure, eg, the palms and soles. The epidermal layer is crossed by hair follicles, sebaceous glands and sweat glands, which arise in the dermis.
The outer surface of the dermis (the papillary layer) is formed of ridges which project into the epidermis. The papillary layer contains blood vessels, lymphatics and nerve endings. The blood supply is distributed between outer vessels that nourish the epidermal cells and deeper vessels that lie just outside the lower subcutaneous layer of fat. The elasticity of skin, and its ability to retain and lose water rapidly, is the consequence of the presence of a network of collagen fibres. Beneath the dermis is the fat-containing subcutaneous layer, which is highly vascularised. The dermis insulates internal structures from excessive heat and reduces heat loss in cold climates. Due to its spongy texture and flexibility, it may also dissipate the effects of physical trauma.
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Citation: Hospital Pharmacist URI: 10976445
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