THE SKIN
The skin is the body’s largest organ (15% of its weight) forming a flexible membrane which covers its entire surface. The skin provides the body with protection via its contact with the external environment resisting mechanical, thermal and chemical aggression to a certain extent. The skin also performs, or contributes to, a broad variety of functions such as metabolic, neurological, immunological and temperature regulation.
ANATOMY
The skin is composed of three main layers:
EPIDERMIS
The outermost layer of the skin, the epidermis forms the body’s external barrier, providing the functions of protection and waterproofing. The thickness of the layer varies depending on the area of the body concerned. On average it is 0.5mm thick but can be as much as 5 mm thick on the soles of the feet.
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DERMIS
The dermis is the living layer of the skin and is highly vascularised. Highly vascularised, its role is as supporting connective tissue. It is rich in fibres that make the skin elastic and strong.
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SUBCUTANEOUS TISSUE
This is a sliding layer of fat cells, performing transition and storage functions for water and fat. It is in close contact with the underlying layers of muscle.
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The epidermis and dermis are clearly separated but are firmly anchored together by the basement membrane that consists of dermal papillae, however there is no clear definition between the dermis and the subcutaneous tissue.
TYPES OF WOUNDS
A wound interrupts skin continuity and integrity. It may be the result of trauma, either minor or severe, or of a pathological/chronic process. The healing prognosis can be very different depending on the depth and mechanism of the lesions.
ACUTE WOUNDS:
Acute wounds can be defined as wounds of sudden onset and of short duration. They include surgical wounds and traumatic wounds that may include:
- Burns
- Abrasions
- Bites and scratches
Traumatic wounds
CHRONIC WOUNDS:
A chronic wound is one that does not heal in the expected time frame (~21 days to a month). An almost permanently inflammatory environment established in the lesion does not allow healing to follow the normal staged procedure.
- Ulcers
- Pressure ulcers
- Diabetic foot ulcers
- Longstanding acute wounds
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INFECTED WOUNDS
Any open wound is susceptible to infection which occurs when there is a host response to bacteria in the wound. Infection delays wound healing and if not readily controlled can spread both locally and systemically leading to serious complications.
Infection
Complications of infection
Local infection or critical colonisation (with local signs such as pus, redness, increased exudate or odor) must be differentiated from infection with regional signs (cellulitis) or systemic signs (ie fever.)