Burns Heat, electricity, radiation, certain chemicals Burn (tissue damage, denatured protein, cell death) Immediate threat: –Dehydration and electrolyte.

Burns

• Heat, electricity, radiation, certain chemicals

Burn (tissue damage, denatured protein, cell death)

• Immediate threat:– Dehydration and electrolyte imbalance, leading to

renal shutdown and circulatory shock

Rule of Nines

• Used to estimate the volume of fluid loss from burns

Figure 5.9

Anterior and posteriorhead and neck, 9%

41/2%41/2%

Anterior and posteriorupper limbs, 18%

Anterior and posteriorlower limbs, 36%

100%

Totals

Anterior and posteriortrunk, 36%

Anteriortrunk,18%

9% 9%(Perineum, 1%)

41/2%

Partial-Thickness Burns

• First degree– Epidermal damage only

• Localized redness, edema (swelling), and pain

• Second degree– Epidermal and upper dermal damage

• Blisters appear

Figure 5.10a

(a) Skin bearing partialthickness burn (1st and 2nd degree burns)

1st degreeburn

2nd degreeburn

Full-Thickness Burns

• Third degree– Entire thickness of skin damaged

• Gray-white, cherry red, or black• No initial edema or pain (nerve endings

destroyed)• Skin grafting usually necessary

Figure 5.10b

(b) Skin bearing fullthickness burn(3rd degree burn)

3rddegreeburn

Severity of Burns

• Critical if:– >25% of the body has second-degree

burns– >10% of the body has third-degree burns– Face, hands, or feet bear third-degree

burns

Epidermal wound healing• Basal cells of epidermis surrounding wound break contact with

basement membrane

• Enlarge and migrate across wound

– EGF (Epidermal Growth Factor) stimulates basal stem cells to

divide and replace migrating cells

• Stop migration due to contact inhibition

• Relocated cells divide to build new epidermal layers and thicken

epidermis

Deep wound healing• Deep wound healing occurs when injury extends to dermis and/or

subcutaneous layer

• Four phases:

– Inflammatory phase

• Blood clot forms loosely binding wound edges

• Inflammation

– eliminates microbes, foreign material and dying tissue

– enhances delivery of helpful cells

– Migratory phase

• Clot becomes scab

• Epithelial cells migrate beneath scab to bridge wound

• Fibroblasts synthesize scar tissue (lots of collagen)

• Blood vessels penetrate scar tissue (forms granulation tissue)

Deep wound healing• Four phases continued:

– Proliferative phase

• Extensive growth of epithelial cells

beneath scab

• Random deposition of collagen fibers

• Blood vessel growth

– Maturation phase

• Epithelium restored to normal

thickness and scab sloughs off

• Collagen fibers become more

organised

• Fibroblasts decrease in number

• Blood vessels restored to normal

Deep wound healing• Scar tissue differs from normal

skin in so far as:

– Collagen fibers more densely

arranged

– Fewer blood vessels

– Fewer hairs, glands, sensory

structures

– Usually lighter in color than

normal skin due to

arrangement of collagen

fibers and scarcity of blood

vessels

From: http://www.abateit.com/scar-pictures.htm

Aging• Most age related changes occur in

dermis

– Wrinkling

• Collagen fibers decrease in

number, stiffen, break apart,

and form shapeless tangles

• Elastic fibres lose elasticity,

thicken into clumps and fray

• Fibroblasts (produce collagen

and elastin) reduce in number

– Reduced skin immunity

• Langerhans cells reduce in

number

• Macrophages become less

efficient

Aging• Sebaceous glands decrease in size

– Results in dry, cracking skin

• more susceptible to infection

• Sweat production diminishes

– Increased susceptibility to heat stroke

• Decrease in number of functioning melanocytes

– Grey hair, change in skin pigmentation

• Some melanocytes enlarge producing age spots

• Migration of cells in epidermis from basal layer to corneum slows

– Skin heals more slowly

– More susceptible to pathology

• Growth of hair and nails slows

– Nails may become more dry and brittle