Lecture Outline
The Integumentary System
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Structure of the Skin
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Also called the cutaneous
membrane or the integument
Covers the entire surface of the
body
Largest organ in the body
Comprised of all 4 tissue types
The integumentary system is
made up of the skin and several
accessory organs
Structure of the Skin
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Regions of the Skin
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Epidermis
Outer, thinner region
Made of stratified squamous epithelium
Five layers (strata)
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Stratum
Stratum
Stratum
Stratum
Stratum
Basale
Spinosum
Granulosum
Lucidum
Corneum
Structure of the Skin
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Stratum Basale
Just superficial to dermis
Constantly dividing and new cells are
pushed to the surface
As cells move toward the surface of the
epidermis, they die and are sloughed off
Cells
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Langerhans cells – macrophages
Melanocytes – produce melanin
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Skin color
Protection from UV radiation
Sensory nerves
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Free nerve endings – pain and temperature
sensations
Tactile cells (Merkel cells) – touch sensations
Structure of the Skin
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Stratum Lucidum
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Just deep to stratum corneum
Found only in thick skin
Provides protection from constant friction
Stratum Corneum
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Tough, uppermost layer of epidermis
Cells are keratinized (hardened)
Keratin prevents water loss and water gain
Serves as a mechanical barrier against
microbes
Structure of the Skin
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Dermis
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Thicker than epidermis
Made of dense, irregular connective tissue
Dermal papillae
Collagenous fibers prevent skin from
being torn
Elastic fibers stretch to allow movement
of muscles and joints
Vascularization of dermis supplies oxygen
and nutrients to cells of dermis and
epidermis
Numerous sensory nerve fibers
Structure of the Skin
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Hypodermis
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Subcutaneous layer located below the
dermis
Composed of loose connective tissue
Energy storage
Insulation
Accessory Structures of the Skin
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Hair
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On all body parts except the palms, soles,
lips, nipples, and portions of the external
reproductive organs
After puberty there is noticeable hair in the
axillary and pelvic regions
Hirsutism – characterized by excessive body
and facial hair in women due to increased
production of male sex hormone
Alopecia – hair loss
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Androgenic alopecia – male pattern baldness
Alopecia areata – sudden onset of patchy hair loss
Accessory Structures of the Skin
• Hair follicles
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Formed from epidermal cells
Located in dermis
Cells become keratinized as they are
pushed out
Hair root – portion of hair within follicle
Hair shaft – portion of hair that continues
beyond the skin
• Sebaceous (oil) glands
• Arrector pili muscle – smooth muscle
attached to hair follicle
Accessory Structures of the Skin
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Nails
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Formed from
specialized epithelial
cells
Nail root – base of
the nail
Nail body – visible
portion of the nail
Cuticles – fold of skin
that hides the root
Epithelial cells
become keratinized
as they move away
from the root
Accessory Structures of the Skin
o Glands –
specialized cells
that produce and
secrete
substances into
ducts
• Sweat glands
• Sebaceous glands
Accessory Structures of the Skin
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Sweat (sudoriferous) glands – active
under stress
Apocrine glands
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Eccrine sweat glands
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Open into hair follicles in anal region, groin, and
armpits
Begin to secrete at puberty
Mammary glands are modified apocrine glands
Open onto surface of skin
Active when body heats up; helps lower body
temperature
Sweat (perspiration) is mostly water, but also
excretes wastes
Ceruminous glands – modified sweat
glands that produce cerumen (earwax)
Accessory Structures of the Skin
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Sebaceous glands
Most are associated with a hair follicle
Secrete an oily substance called sebum
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Lubricates and waterproofs hair and skin
Weakens or kills bacteria on skin surface
If sebum collects, whiteheads or
blackheads form
Acne vulgaris – inflammation of the
sebaceous glands
Disorders of the Skin
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Athlete’s foot – fungal infection often
involving skin of the toes and soles
Impetigo – bacterial infection common
in young children
Psoriasis – chronic condition where skin
develops pink or reddish patches
Eczema – inflammation of the skin
Dandruff – caused by a dry scalp
producing flaking and itching
Urticaria (hives) – allergic reaction
causing reddish, elevated, and often
itchy patches
Disorders of the Skin
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Skin Cancer
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Begins with mutation of the skin cell
DNA
Nonmelanoma cancers – less likely to
metastasize
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Basal cell carcinoma
Squamous cell carcinoma
Melanoma cancers
Disorders of the Skin
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Basal cell carcinoma
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Most common type of skin
cancer
Ultraviolet (UV) radiation
causes epidermal basal
cells to form a tumor
Signs are varied
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Open sore that will not
heal
Recurring reddish patch
Smooth, circular growth
with a raised edge
Shiny bump
Pale mark
95% of patients are easily
cured by removal
Disorders of the Skin
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Squamous cell carcinoma
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Five times less common
than basal cell carcinoma
More likely to spread than
basal cell carcinoma
About 1% of cases result
in death
Triggered by excessive UV
exposure
Signs are the same as
those for basal cell
carcinoma, but may also
resemble a wart or scaly
growth that bleeds and
scabs
Disorders of the Skin
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Melanoma
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More likely to be malignant
Starts in the melanocytes
Has the appearance of an
unusual mole
Warning signs
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Asymmetry
Irregular borders
Uneven color
Diameter greater than
6mm
Most common in fairskinned persons
Disorders of the Skin
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Wound Healing
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Causes an inflammatory response
Steps in wound healing
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A blood clot forms
White blood cells and fibroblasts move to
the injured area
Fibroblasts pull the margins of the wound
together and promote tissue regeneration
The basal layer of the epidermis produces
new cells
Proliferating fibroblasts form a scar
Disorders of the Skin
Disorders of the Skin
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Burns
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Usually caused by heat
Burn severity affected by:
Extent of the burned area
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“Rule of nines” is a technique used to estimate
the extent of a burn
Lund-Browder chart is used for children
Disorders of the Skin
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Depth of the burn
First degree burn
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Second degree burn
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Extends through entire epidermis and part of the
dermis
Redness, pain, and blistering
Third degree burn
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Only epidermis affected
Redness and pain
No blisters or swelling occurs
Destroys entire thickness of the skin
Surface of wound is leathery and may be brown, tan,
black, white, or red
Patient feels no pain
Fourth degree burn – involve tissues down to
the bone
Disorders of the Skin
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Burns are considered a critical injury if:
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Second-degree burns cover 25% or more of the
patient’s body
Third-degree burns cover 10% or more of the
patient’s body
Any portion of the body has a fourth-degree burn
Third-degree burns occur on the face, hands, or
feet
Major concerns associated with severe
burns:
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Fluid loss
Heat loss
Bacterial infection
Effects of Aging
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Rate of cell mitosis decreases
Dermis becomes thinner and the dermal
papillae flatten
Adipose tissue in the hypodermis decreases
Collagen decreases
Elastic fibers in upper layer of dermis are lost
and those in the lower layer become thicker,
less elastic, and disorganized
Wrinkles form because of:
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Loose epidermis
Fewer fibers
Less padding in hypodermis
Effects of Aging
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Limited homeostatic adjustment to
heat because of:
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Less vasculature (fewer blood
vessels)
Fewer sweat glands
Number of hair follicles decreases
Reduced number of sebaceous
glands
Number of melanocytes decrease
Homeostasis
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Functions of the Skin
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Protection
Safeguards from physical trauma
Protection from UV radiation
Help prevent bacterial invasion
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Sebum is acidic, which retards growth of
bacteria
Langerhans cells phagocytize pathogens and
alert the immune system to the presence of
pathogens
Homeostasis
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Regulation of water loss
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Keratinized cells prevent water from
entering the body
Water is excreted through perspiration
Vitamin D production
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Small amounts of UV radiation are
needed
Vitamin D leaves the skin and enters the
liver and kidneys
Homeostasis
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Gathers sensory information
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Sensory receptors in the epidermis and
dermis are specialized for touch,
pressure, pain, hot, and cold
Receptors supply the central nervous
system with information about the
external environment
Homeostasis
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Helps regulate body temperature
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If body temperature rises, blood vessels
in the skin dilate and sweat glands
become active
If the outer temperature is cool, blood
vessels constrict
Arrector pili muscles contract, but
insulating effect is absent in humans
Hyperthermia - body temperature above
normal
Hypothermia – body temperature below
normal