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increasing or decreasing sweat production, superficial blood flow,

or both.

2.

Protection. The skin acts as a barrier to protect the body

from micro�organism invasion, ultraviolet (UV) radiation, abra�

sion, chemicals, and dehydration.

3.

Sensation. Multiple sensory cells within the skin detect

pain, temperature, and touch.

4.

Excretion. Heat, sweat, and water can be excreted from

the skin.

5.

Immunity. Normal periodic loss of epidermal cells removes

micro-organisms from the body surface, and immune cells in the

skin transport antigens from outside the body to the antibody cells

of the immune system.

6.

Blood reservoir. Large volumes of blood can be shunted

from rhe skin to central organs or muscles as needed.

7. Vitamin D synthesis. Modified cholesterol molecules ate

convened to vitamin 0 when exposed to UV radiation.

438 ACUTE CAR£ HANDBOOK FOR PHYSICAL TIII;RAJ'ISTS

Table 7-1. Normal Skin Layers: Structure and Function

Layer

Composition

Function

Epidermis

Strarum

Dead

Tough outer layer that protectS

corneum

keratinocytes

deeper layers of epidermis

Pigment layer

Melallocytes

Produces melanin to prevent

ultraviolet absorption

Stratum

Mature

Produces keratin to make the skin

granulosum

keratinocytes

waterproof

Langerhans' cells

Interacts with immune cells

Stratum

Keratinocytes

Undergoes mirosis to continue skin

spinosum

cell development but to a lesser

degree than basal

Stratum basale

ew keratinocytes

The origin of skin cells, which

undergoes mitosis, then moves

superficially

Merkel's cells

Detects touch

Dermis

Papillary layer

Areolar

Binds epidermis and dermis

connective

rogether

tissue

Meissner's

Detects light rouch

corpuscles

Blood and lymph

Provides circulation and drainage

vessels

Free nerve endings

Detects heat and pain

Reticular layer

Collagen, elastin,

Provides strength and resilience

and reticular

fibers

Hypodermis

Subcutaneous fat

Provides insulation and shock

absorption

Pacinian cells

Detects pressure

Free nerve endings

Detects cold

Source: Data from GA Thibodeau, KT Panon (cds), Structure and Function of the I�y

(11th ed). St Louis: Mosby, 2000.

BURNS AND WOUNDS 439

Pathophysiology of Burns

Skin and body tissue destrucrion occurs from rhe absorprion of heat

energy and results in tissue coagulation. This coagulation is depicted

in zones (Figure 7-2). The ZOl1e of coagu/ali01l, locared in the cemer of

the burn, is the area of greatest damage and contains nonviable tissue

referred to as eschar. Alrhough eschar covers rhe surface and may

appear to take rhe place of skin, ir does nor have any of rhe characreristics or functions of normal skin. Instead, eschar is constrictive, attracts micro-organisms, and houses burn toxins that may circulate

throughout rhe body.' The Z01le of stasis, which surrounds rhe zone of

coagularion, comains marginally viable rissue. The Z01le of hyperemia, rhe ourermosr area, is the least damaged and heals rapidly.

Sequelae of Bum I1Ijury

A series of physiologic evems occurs afrer a burn (Figure 7-3). The

physical rherapisr musr appreciare rhe mulrisysrem effecrs of a

burn injury-namely, rhar rhe merabolic demands of the body

increase dramarically. Tissue damage or organ dysfuncrion can be

immediate or delayed, minor or severe, and local or systemic. A

A

B

c

Epidermis

Dermis

Subcutaneous

tissue

Figure 7-2. The ZOlles of coagulatioll. Superficial bum (AJ. Partial-thickness

bllm (8). Ful/-thickness bum (e). (Modified {rolll WG Wil/iallls, LG Phil/ips.

Pathophysiology of the Bum Wound. 111 DN Hemdo" {ed!. Total Burn Care.

London: Saunders, 1996;65,)