Introduction to burnsThe skin has an important role to play in the fluid and temperature regulation of thebody. If enough skin area is injured, the ability to maintain that control can be lost.The skin also acts as a protective barrier against the bacteria and viruses thatinhabit the world outside the body.The anatomy of the skin is complex, and there are many structures within thelayers of the skin. There are three layers: 1. Epidermis, the outer layer of the skin 2. Dermis, made up of collagen and elastic fibers and where nerves, blood vessels, sweat glands, and hair follicles reside. 3. Hypodermis or subcutaneous tissue, where larger blood vessels and nerves are located. This is the layer of tissue that is most important in temperature regulation.The amount of damage that a burn can cause depends upon its location, its depth,and how much body surface area that it involves.Burns are classified based upon their depth.A first degree burn is superficial and causes local inflammation of the skin.Sunburns often are categorized as first degree burns. The inflammation ischaracterized by pain, redness, and a mild amount of swelling. The skin may bevery tender to touch.Second degree burns are deeper and in addition to the pain, redness andinflammation, there is also blistering of the skin.Third degree burns are deeper still, involving all layers of the skin, in effect killingthat area of skin. Because the nerves and blood vessels are damaged, third degreeburns appear white and leathery and tend to be relatively painless.Burns are not static and may mature. Over a few hours a first degree burn mayinvolve deeper structures and become second degree. Think of a sunburn thatblisters the next day. Similarly, second degree burns may evolve into third degreeburns.Regardless of the type of burn, inflammation and fluid accumulation in and aroundthe wound occur. Moreover, it should be noted that the skin is the bodys firstdefense against infection by microorganisms. A burn is also a break in the skin, andthe risk of infection exists both at the site of the injury and potentially throughoutthe body.
Only the epidermis has the ability to regenerate itself. Burns that extend deepermay cause permanent injury and scarring and not allow the skin in that area toreturn to normal function.The significance of the amount of body area burnedIn addition to the depth of the burn, the total area of the burn is significant. Burnsare measured as a percentage of total body area affected. The "rule of nines" isoften used, though this measurement is adjusted for infants and children. Thiscalculation is based upon the fact that the surface area of the following parts of anadult body each correspond to approximately 9% of total (and the total body areaof 100% is achieved): Head = 9% Chest (front) = 9% Abdomen (front) = 9% Upper/mid/low back and buttocks = 18% Each arm = 9% Each palm = 1% Groin = 1% Each leg = 18% total (front = 9%, back = 9%)As an example, if both legs (18% x 2 = 36%), the groin (1%) and the front chestand abdomen were burned, this would involve 55% of the body. ]
Only second and third degree burn areas are added together to measure total bodyburn area. While first degree burns are painful, the skin integrity is intact and it isable to do its job with fluid and temperature maintenance.If more than15%-20% of the body is involved in a burn, significant fluid may belost. Shock may occur if inadequate fluid is not provided intravenously. TheParkland formula (named for the trauma hospital in Dallas) estimates the amountof fluid required in the first few hours of care following a burn: 4cc/ kg of weight/% burn = initial fluid requirement in the first 24 hours, with half given in the first 8 hours. As an example: A 175lb (or 80kg) patient with 25% burn will need 4cc x 80kg x 25%, or 8000cc of fluid in the first 24 hours, or more than 7 pounds of fluid.As the percentage of burn surface area increases, the risk of death increases aswell. Patients with burns involving less than 20% of their body should do well, butthose with burns involving greater than 50% have a significant mortality risk,depending upon a variety of factors, including underlying medical conditions andage.Skin Anatomy and PhysiologyBeautiful, healthy skin is determined by the healthy structure and proper functionof components within the skin. To maintain beautiful skin, and slow the rate atwhich it ages, the structures and functions of the skin must be supplemented andprotected. In order to know how to supplement and protect the skin, its importantto know more about the skins basic anatomy and composition. There are threemajor components of the skin. First is the hypodermis, which is subcutaneous (justbeneath the skin) fat that functions as insulation and padding for the body. Next isthe dermis, which provides structure and support. Last is the epidermis, whichfunctions as a protective shield for the body.HypodermisThe hypodermis is the deepest section of the skin. The hypodermis refers to the fattissue below the dermis that insulates the body from cold temperatures andprovides shock absorption. Fat cells of the hypodermis also store nutrients andenergy. The hypodermis is the thickest in the buttocks, palms of the hands, andsoles of the feet. As we age, the hypodermis begins to atrophy, contributing to thethinning of aging skin.Dermis
The dermis is located between the hypodermis and the epidermis. It is a fibrousnetwork of tissue that provides structure and resilience to the skin. While dermalthickness varies, it is on average about 2 mm thick. The major components of thedermis work together as a network. This mesh-like network is composed ofstructural proteins (collagen and elastin), blood and lymph vessels, and specializedcells called mast cells and fibroblasts. These are surrounded by a gel-like substancecalled the ground substance, composed mostly of glycosaminoglycans. The groundsubstance plays a critical role in the hydration and moisture levels within the skin.The most common structural component within the dermis is the protein collagen.It forms a mesh-like framework that gives the skin strength and flexibility. Theglycosaminoglycans—moisture binding molecules—enable collagen fibers to retainwater and provide moisture to the epidermis. Another protein found throughout thedermis is the coil-like protein, elastin, which gives the skin its ability to return to itsoriginal shape after stretching. In other words, elastin provides the skin with itselasticity. Both collagen and elastin proteins are produced in specialized cells calledfibroblasts, located mostly in the upper edge of the dermis bordering the epidermis.Intertwined throughout the dermis are blood vessels, lymph vessels, nerves, andmast cells. Mast cells are specialized cells that play an important role in triggeringthe skin’s inflammatory response to invading microorganisms, allergens, andphysical injury. The blood vessels in the dermis help in thermoregulation of thebody by constricting or dilating to conserve or release heat. They also aid inimmune function and provide oxygen and nutrients to the lower layers of theepidermis. These blood vessels do not extend into the epidermis. Nourishment thatdiffuses into the epidermis only reaches the very bottom layers. The cells in theupper layers of the epidermis are dead because they do not receive oxygen andnutrients. The junction between the dermis and epidermis is a wave-like border thatprovides an increased surface area for the exchange of oxygen and nutrientsbetween the two sections. Along this junction are projections called dermal papillae.As you age, your dermal papillae tend to flatten, decreasing the flow of oxygen andnutrients to the epidermis.EpidermisThe epidermis is the outermost layer of the skin. Categorized into five horizontallayers, the epidermis actually consists of anywhere between 50 cell layers (in thinareas) to 100cell layers (in thick areas). The average epidermal thickness is 0.1millimeters, which is about the thickness of one sheet of paper. The epidermis actsas a protective shield for the body and totally renews itself approximately every 28days. The first layer of the epidermis is the stratum basale. This is the deepestlayer of the epidermis and sits directly on top of the dermis. It is a single layer ofcube-shaped cells. New epidermal skin cells, called keratinocytes, are formed in thislayer through cell division to replace those shed continuously from the upper layers
of the epidermis. This regenerative process is called skin cell renewal. As we age,the rate of cell renewal decreases. Melanocytes, found in the stratum basale, areresponsible for the production of skin pigment, or melanin. Melanocytes transfer themelanin to nearby keratinocytes that will eventually migrate to the surface of theskin. Melanin is photoprotective: it helps protect the skin against ultravioletradiation (sun exposure).The second layer of the epidermis is the stratumspinosum, or the prickle-cell layer. Thestratum spinosum is composed of 8-10layers of polygonal (many sided) keratinocytes. In this layer, keratinocytes arebeginning to become somewhat flattened. The third layer is called the stratumgranulosum, or the granular layer. It is composed of 3-5 layers of flattenedkeratin—a tough, fibrous protein that gives skin its protective properties. Cells inthis layer are too far from the dermis to receive nutrients through diffusion, so theybegin to die. The fourth layer in the epidermis is called the stratum lucidum, or theclear layer. This layer is present only in the fingertips, palms, and soles of the feet.It is 3-5 layers of extremely flattened cells. The fifth layer, or horny layer, is calledthe stratum corneum. This is the top, outermost layer of the epidermis and is 25-30layers of flattened, dead keratinocytes. This layer is the real protective layer of theskin. Keratinocytes in the stratum corneum are continuously shed by friction andreplaced by the cells formed in the deeper sections of the epidermis. In betweenthe keratinocytes in the stratum corneum are epidermal lipids(ceramides, fattyacids, and lipids) that act as a cement (or mortar) between the skin cells(bricks).This combination of keratinocytes with interspersed epidermal lipids (brickandmortar) forms a waterproof moisture barrier that minimizes transepidermalwater loss(TEWL) to keep moisture in the skin. This moisture barrier protectsagainst invading microorganisms, chemical irritants, and allergens. If the integrityof the moisture barrier is compromised, the skin will become vulnerable to dryness,itching, redness, stinging, and other skin care concerns. In the very outer layers ofthe stratum corneum, the moisture barrier has a slightly acidic pH (4.5 to 6.5).These slightly acidic layers of the moisture barrier are called the acid mantle. Theacidity is due to a combination of secretions from the sebaceous and sweat glands.The acid mantle functions to inhibit the growth of harmful bacteria and fungi. Theacidity also helps maintain the hardness of keratin proteins, keeping them tightlybound together. If the skins surface is alkaline, keratin fibers loosen and soften,losing their protective properties. When the pH of the acid mantle is disrupted(becomes alkaline)—aside effect of common soaps—the skin becomes prone toinfection, dehydration, roughness, irritation, and noticeable flaking. A number ofcomponents are common to both the dermis and epidermis. These are: pores, hair,sebaceous glands, and sweat glands. Pores are formed by a folding-in of theepidermis into the dermis. The skin cells that line the pore (keratinocytes) arecontinuously shed, just like the cells of the epidermis at the top of the skin. Thekeratinocytes being shed from the lining of the pore can mix with sebum and clogthe pore. This is the precursor to acne. If oil builds up inside pores, or if tissue
surrounding the pore becomes agitated, pores may appear larger. Hair grows out ofthe pores and is composed of dead cells filled with keratin proteins. At the base ofeach hair is a bulb-like follicle that divides to produce new cells. The follicle isnourished by tiny blood vessels and glands. Hair prevents heat loss and helpsprotect the epidermis from minor abrasions and exposure to the suns rays.Sebaceous glands are usually connected to hair follicles and secrete sebum to helplubricate the follicle as it grows. Sebum also contributes to the lipids and fatty acidswithin the moisture barrier. Oil production within the sebaceous gland is regulatedby androgen levels (hormones such as testosterone).Sweat glands are long, coiled,hollow tubes of cells. The coiled section is where sweat is produced, and the longportion is a duct that connects the gland to the pore opening on the skins surface.Perspiration excreted by the sweat glands helps cool the body, hydrate the skin,eliminate some toxins (i.e., salt), and maintain the acid mantle. Understanding howskin is constructed can help you better care for your skin.EtiologyThermal burns may result from any external heat source (flame, hot liquids, hotsolid objects, or, occasionally, steam). Fires may also result in toxic smokeinhalationRadiation burns most commonly result from prolonged exposure to solarultraviolet radiation (sunburn—see Reactions to Sunlight: Sunburn) but may resultfrom prolonged or intense exposure to other sources of ultraviolet radiation (eg,tanning beds) or from exposure to sources of x-ray or other nonsolar radiation (seePoisoning: Caustic Ingestion).Chemical burns may result from strong acids, strong alkalis (eg, lye, cement),phenols, cresols, mustard gas, phosphorus, and certain petroleum products (eg,gasoline, paint thinner). Skin and deeper tissue necrosis caused by these agentsmay progress over several hours.Electrical burns (see also Electrical and Lightning Injuries: Electrical Injuries)result from heat generation and electroporation of cell membranes associated withmassive current of electrons. Electrical burns may cause extensive deep tissuedamage to electrically conductive tissues, such as muscles and nerves, despiteminimal apparent cutaneous injury.Events associated with a burn (eg, jumping from a burning building, being struckby debris, motor vehicle crash) may cause other injuries. Abuse should beconsidered in young children and elderly patients with burns.