burns heat, electricity, radiation, certain chemicals burn (tissue damage, denatured protein, cell...
TRANSCRIPT
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