1. Introduction to burns
The skin has an important role to play in the fluid and temperature regulation of the
body. 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 that
inhabit the world outside the body.
The anatomy of the skin is complex, and there are many structures within the
layers 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 is
characterized by pain, redness, and a mild amount of swelling. The skin may be
very tender to touch.
Second degree burns are deeper and in addition to the pain, redness and
inflammation, there is also blistering of the skin.
Third degree burns are deeper still, involving all layers of the skin, in effect killing
that area of skin. Because the nerves and blood vessels are damaged, third degree
burns 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 may
involve deeper structures and become second degree. Think of a sunburn that
blisters the next day. Similarly, second degree burns may evolve into third degree
burns.
Regardless of the type of burn, inflammation and fluid accumulation in and around
the wound occur. Moreover, it should be noted that the skin is the body's first
defense against infection by microorganisms. A burn is also a break in the skin, and
the risk of infection exists both at the site of the injury and potentially throughout
the body.

2. Only the epidermis has the ability to regenerate itself. Burns that extend deeper
may cause permanent injury and scarring and not allow the skin in that area to
return to normal function.
The significance of the amount of body area burned
In addition to the depth of the burn, the total area of the burn is significant. Burns
are measured as a percentage of total body area affected. The "rule of nines" is
often used, though this measurement is adjusted for infants and children. This
calculation is based upon the fact that the surface area of the following parts of an
adult body each correspond to approximately 9% of total (and the total body area
of 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 chest
and abdomen were burned, this would involve 55% of the body.
]

3. Only second and third degree burn areas are added together to measure total body
burn area. While first degree burns are painful, the skin integrity is intact and it is
able to do its job with fluid and temperature maintenance.
If more than15%-20% of the body is involved in a burn, significant fluid may be
lost. Shock may occur if inadequate fluid is not provided intravenously. The
Parkland formula (named for the trauma hospital in Dallas) estimates the amount
of 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 as
well. Patients with burns involving less than 20% of their body should do well, but
those with burns involving greater than 50% have a significant mortality risk,
depending upon a variety of factors, including underlying medical conditions and
age.
Skin Anatomy and Physiology
Beautiful, healthy skin is determined by the healthy structure and proper function
of components within the skin. To maintain beautiful skin, and slow the rate at
which it ages, the structures and functions of the skin must be supplemented and
protected. In order to know how to supplement and protect the skin, it's important
to know more about the skin's basic anatomy and composition. There are three
major components of the skin. First is the hypodermis, which is subcutaneous (just
beneath the skin) fat that functions as insulation and padding for the body. Next is
the dermis, which provides structure and support. Last is the epidermis, which
functions as a protective shield for the body.
Hypodermis
The hypodermis is the deepest section of the skin. The hypodermis refers to the fat
tissue below the dermis that insulates the body from cold temperatures and
provides shock absorption. Fat cells of the hypodermis also store nutrients and
energy. The hypodermis is the thickest in the buttocks, palms of the hands, and
soles of the feet. As we age, the hypodermis begins to atrophy, contributing to the
thinning of aging skin.
Dermis

4. The dermis is located between the hypodermis and the epidermis. It is a fibrous
network of tissue that provides structure and resilience to the skin. While dermal
thickness varies, it is on average about 2 mm thick. The major components of the
dermis work together as a network. This mesh-like network is composed of
structural proteins (collagen and elastin), blood and lymph vessels, and specialized
cells called mast cells and fibroblasts. These are surrounded by a gel-like substance
called the ground substance, composed mostly of glycosaminoglycans. The ground
substance 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. The
glycosaminoglycans—moisture binding molecules—enable collagen fibers to retain
water and provide moisture to the epidermis. Another protein found throughout the
dermis is the coil-like protein, elastin, which gives the skin its ability to return to its
original shape after stretching. In other words, elastin provides the skin with its
elasticity. Both collagen and elastin proteins are produced in specialized cells called
fibroblasts, located mostly in the upper edge of the dermis bordering the epidermis.
Intertwined throughout the dermis are blood vessels, lymph vessels, nerves, and
mast cells. Mast cells are specialized cells that play an important role in triggering
the skin’s inflammatory response to invading microorganisms, allergens, and
physical injury. The blood vessels in the dermis help in thermoregulation of the
body by constricting or dilating to conserve or release heat. They also aid in
immune function and provide oxygen and nutrients to the lower layers of the
epidermis. These blood vessels do not extend into the epidermis. Nourishment that
diffuses into the epidermis only reaches the very bottom layers. The cells in the
upper layers of the epidermis are dead because they do not receive oxygen and
nutrients. The junction between the dermis and epidermis is a wave-like border that
provides an increased surface area for the exchange of oxygen and nutrients
between 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 and
nutrients to the epidermis.
Epidermis
The epidermis is the outermost layer of the skin. Categorized into five horizontal
layers, the epidermis actually consists of anywhere between 50 cell layers (in thin
areas) to 100cell layers (in thick areas). The average epidermal thickness is 0.1
millimeters, which is about the thickness of one sheet of paper. The epidermis acts
as a protective shield for the body and totally renews itself approximately every 28
days. The first layer of the epidermis is the stratum basale. This is the deepest
layer of the epidermis and sits directly on top of the dermis. It is a single layer of
cube-shaped cells. New epidermal skin cells, called keratinocytes, are formed in this
layer through cell division to replace those shed continuously from the upper layers

5. 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, are
responsible for the production of skin pigment, or melanin. Melanocytes transfer the
melanin to nearby keratinocytes that will eventually migrate to the surface of the
skin. Melanin is photoprotective: it helps protect the skin against ultraviolet
radiation (sun exposure).The second layer of the epidermis is the stratum
spinosum, or the prickle-cell layer. Thestratum spinosum is composed of 8-10
layers of polygonal (many sided) keratinocytes. In this layer, keratinocytes are
beginning to become somewhat flattened. The third layer is called the stratum
granulosum, or the granular layer. It is composed of 3-5 layers of flattened
keratin—a tough, fibrous protein that gives skin its protective properties. Cells in
this layer are too far from the dermis to receive nutrients through diffusion, so they
begin to die. The fourth layer in the epidermis is called the stratum lucidum, or the
clear 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 called
the stratum corneum. This is the top, outermost layer of the epidermis and is 25-30
layers of flattened, dead keratinocytes. This layer is the real protective layer of the
skin. Keratinocytes in the stratum corneum are continuously shed by friction and
replaced by the cells formed in the deeper sections of the epidermis. In between
the keratinocytes in the stratum corneum are epidermal lipids(ceramides, fatty
acids, and lipids) that act as a cement (or mortar) between the skin cells(bricks).
This combination of keratinocytes with interspersed epidermal lipids (brick
andmortar) forms a waterproof moisture barrier that minimizes transepidermal
water loss(TEWL) to keep moisture in the skin. This moisture barrier protects
against invading microorganisms, chemical irritants, and allergens. If the integrity
of 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 of
the 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. The
acidity 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. The
acidity also helps maintain the hardness of keratin proteins, keeping them tightly
bound together. If the skin's 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 to
infection, dehydration, roughness, irritation, and noticeable flaking. A number of
components 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 the
epidermis into the dermis. The skin cells that line the pore (keratinocytes) are
continuously shed, just like the cells of the epidermis at the top of the skin. The
keratinocytes being shed from the lining of the pore can mix with sebum and clog
the pore. This is the precursor to acne. If oil builds up inside pores, or if tissue

6. surrounding the pore becomes agitated, pores may appear larger. Hair grows out of
the pores and is composed of dead cells filled with keratin proteins. At the base of
each hair is a bulb-like follicle that divides to produce new cells. The follicle is
nourished by tiny blood vessels and glands. Hair prevents heat loss and helps
protect the epidermis from minor abrasions and exposure to the sun's rays.
Sebaceous glands are usually connected to hair follicles and secrete sebum to help
lubricate the follicle as it grows. Sebum also contributes to the lipids and fatty acids
within the moisture barrier. Oil production within the sebaceous gland is regulated
by 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 long
portion is a duct that connects the gland to the pore opening on the skin's 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 how
skin is constructed can help you better care for your skin.
Etiology
Thermal burns may result from any external heat source (flame, hot liquids, hot
solid objects, or, occasionally, steam). Fires may also result in toxic smoke
inhalation
Radiation burns most commonly result from prolonged exposure to solar
ultraviolet radiation (sunburn—see Reactions to Sunlight: Sunburn) but may result
from 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 (see
Poisoning: 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 agents
may progress over several hours.
Electrical burns (see also Electrical and Lightning Injuries: Electrical Injuries)
result from heat generation and electroporation of cell membranes associated with
massive current of electrons. Electrical burns may cause extensive deep tissue
damage to electrically conductive tissues, such as muscles and nerves, despite
minimal apparent cutaneous injury.
Events associated with a burn (eg, jumping from a burning building, being struck
by debris, motor vehicle crash) may cause other injuries. Abuse should be
considered in young children and elderly patients with burns.