Overview, Pathophysiology, Quantifying Burn Severity. Skin Anatomy and Function. Skin is the largest organ of the body. It has 3 major tissue layers. Epidermis. The outermost layer, the epidermis, is composed of stratified epithelium. Epidermis has 2 components, an outer layer of anucleate cornified cells (stratum corneum) that covers inner layers of viable cells (Malpighian layers) from which the cornified surface cells arise by differentiation. The stratum corneum acts as a barrier to impede the entrance of microorganisms and toxic substances while allowing the body to retain water and electrolytes. Malpighian layers provide a continuous production of cornified cells. Malpighian layers can be further subdivided into the germinal basal cell layer, stratum spinosum, and stratum granulosum. Dermis. Beneath the epidermis is the dermis, which is composed of a dense fibroelastic connective- tissue stroma containing collagen and elastic fibers and an extracellular gel termed ground substance. This amorphous gel comprises an acid mucopolysaccharide protein combined with salts, water, and glycoproteins; it may contribute to salt and water balance, serve as a support for other components of the dermis and subcutaneous tissue, and participate in collagen synthesis. The dermal layer contains an extensive vascular and nerve network, special glands, and appendages that communicate with the overlying epidermis. The dermis is divided into 2 parts. The most superficial portion, the papillary dermis, is molded against the epidermis and contains superficial elements of the microcirculation of the skin. It consists of relatively cellular, loose connective tissue with smaller, fewer collagen and elastic fibers than the underlying reticular dermis. Within the papillary dermis, dermal elevations indent the inner surface of the epidermis. Between the dermal papillae, the downward projections of the epidermis appear peglike and are termed rete pegs. In the reticular portion of the dermis, collagen and elastic fibers are thicker and greater in number. Fewer cells and less ground substance are found in the reticular dermis than in the papillary dermis. Thickness of the dermis varies from 1- 4 mm in different anatomic regions and is thickest in the back, followed by the thigh, abdomen, forehead, wrist, scalp, palm, and eyelid. Thickness varies with the individual's age. It is thinnest in the very old, where it is often atrophic, and in the very young, where it is not fully developed. Subcutaneous tissue. The third layer of skin is subcutaneous tissue, which is composed primarily of areolar and fatty connective tissue. This layer shows great regional variations in thickness and adipose content. It contains skin appendages, glands, and hair follicles. Hair follicles extend in deep narrow pits or pockets that traverse the dermis to varying depths and usually extend into the subcutaneous tissue. Each hair follicle consists of a shaft that projects above the surface and a root that is embedded within the skin. Apocrine and eccrine sweat glands. There are 2 types of sweat glands in skin: apocrine and eccrine. Apocrine glands are epitrichial because they have a duct that opens into a hair follicle. Apocrine glands are largely confined to the axillary and perineal region and do not become functional until just after puberty. Eccrine glands are simple, coiled, tubular glands usually extending into the papillary dermis. Eccrine glands are atrichial because their duct opens onto the skin surface independently of a hair follicle. Eccrine glands are found over the entire body surface, except the margins of the lips, eardrum, inner surface of the prepuce, and glans penis. Sebaceous glands are simple or branched alveolar glands, usually connected to the hair follicles. Sebaceous glands unconnected with hair follicles occur along the margin of the lips, in the nipples, in the glans and prepuce of the penis, and in the labia minora. Depending on the depth of burn injury, epithelial repair can be accomplished from local epithelial elements and skin appendages. When skin is burned, the damaged stratum corneum allows the invasion of microorganisms, and the Langerhans cells, which mediate local immune responses, also are damaged. In burn patients with severe injuries, their systemic immune response is diminished, making them susceptible to serious infections. Heat transfer from heating agent to skin. Severity of burn injury is related to the rate at which heat is transferred from the heating agent to the skin. Rate of heat transfer depends on the heat capacity of the agent, temperature of the agent, duration of contact with the agent, transfer coefficient, and specific heat and conductivity of the local tissues. Heat capacity: Capacity of a material to hold heat energy is determined by both the specific heat and the heat capacity of the material. Specific heat of a material: This is defined as the ratio of the amount of heat required to raise a specific mass of the material 1 degree in temperature, to the amount of heat required to raise an equal mass of a reference substance (usually water) 1 degree in temperature. Heat capacity: This refers to a quantity of heat a material contains when it comes in contact with skin. Quantity of heat stored depends on the specific heat of the material and the amount and temperature of the material. The importance of heat capacity as a determinant of severity of burn injury is best illustrated by comparing the amount of heat stored in 1. Specific heat of water is 4. W xsec/g x. K (watt times seconds of heat per gram mass times degrees Kelvin). If these 2 materials come in contact with skin, they give up their heat by cooling while skin accepts the heat by increasing its temperature. If the temperature of each material decreases by 6. Even if the initial temperatures of the 2 materials are identical, heat available from water is much more likely to produce a severe injury. The specific heat of water (most common cause of scald burns) is the highest of all the gases, metals, and solids tested to date, with the exception of ammonia and ether. Temperature. Initial temperature of a material at the instant of contact is also an important determinant of burn severity. Many materials (eg, water) cannot be heated beyond a certain temperature without changing state. Water can only be heated to 1. Because more joules are required to produce steam, this additional heat transfer accounts for the severe burns caused by steam injury. When other liquids reach a specific temperature, they ignite or oxidize by combining with oxygen. The flash point of the liquid is the temperature at which the vapors of a volatile liquid mixed with air spontaneously ignite. A flammable liquid is defined as any liquid having a flash point less than 3. Liquids with a flash point above this temperature are considered combustible. In addition to their high temperatures, burning liquids also may ignite the victim's clothing, thereby further exacerbating severity of the injury. Duration of contact. Human skin can tolerate temperatures as high as 4. Duration of contact between a liquid and skin depends on both the viscosity of the liquid and the manner in which it is applied to the victim's skin. When hot liquid is splashed on a person, as in a spill scald, it usually flows down the body in a rate of descent that depends on the fluid's viscosity. Although water streams to the ground unless impeded by clothing, viscous oils and greases usually cling to a victim's skin, prolonging duration of exposure and extent of injury. In immersion scalds, duration of contact between the hot liquid and the skin is considerably longer than that with spill scalds, thereby increasing the severity of injury. Certain populations are at high risk of suffering immersion scald burns, including children younger than 5 years, older persons (6. Individuals in these high- risk groups tend to have a slower reaction time and a physical inability to escape from hot water. The Goals of Meditation. Before discussing the techniques of meditation, it is important that we first define its goals. That is, why does one meditate? Safety First Cafeteria Safety Fire Prevention / Life Safety Most fires begin in the kitchen. Make sure all fire exits are accessible. Do not block exits, even. Immersion burns commonly cover a large percentage of total body surface area (TBSA), almost twice that of other scald burns, which contributes to their high rate of morbidity and mortality. Immersion burns caused by child abuse can be distinguished from accidental burns by the pattern and site of the burn, histories given by the caretaker and patient, and a medical history of scars representing previous abuse.
Nonaccidental burns often have clear- cut edges, as found in . Spill scald burns, on the other hand, more often have uneven, fuzzy edges as a result of the victim's attempts to escape the hot liquid. Burns from abuse tend to occur on the back of hands and feet, the buttocks and perineum, and legs. Accidental burns, such as those caused by a child spilling a cup of coffee, more often cause burns on the head, trunk, and palmar surface of hands and feet. Physical evidence of previous injuries, such as craterlike cigarette burn scars or bruises, also suggests abuse. Heat transfer. Even when a substance possesses sufficient heat to cause a burn injury, it will not do so unless its heat can be transferred to the skin. This ability to transfer heat between 2 different materials is regulated by the heat transfer coefficient, which is defined as the amount of heat that passes through a unit area of contact between 2 materials when the temperature difference between these materials is 1 degree. Three different methods of heat transfer exist: conduction, convection, and radiation. The simplest method of heat transfer is conduction, which occurs when a hot solid object comes in direct contact with the skin. Convection is the transfer of heat by a material that involves the physical movement of the material itself and is determined by heat conduction and by energy storage and mixing motion. Convection is most important as the mechanism of energy transfer between skin and a heated liquid or gas. Hot water spilling on skin transfers heat by convection between the water droplets and the skin surface.
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