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The Integumentary system
Chapter 5
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The Skin
• Most accessible organ/system to the outside world
• 16% of total body weight• Constantly under attack from the environment• The human body’s first line of defense.
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The integument
• Body covering• Interconnected with blood vessels and
sensory receptors.
Two Major Components1. Cutaneous membrane2. Accessory structures
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Cutaneous Membrane
EpidermisDermis
Superficial Underlying
connective tissues
Blood Vessels
NervesGlands
Accessory Structures
Hair, nails, exocrine glands
Primarily found in the dermis but protrude (poke through) the epidermis.
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Yet another layer. . .
• Below the dermis you can find the hypodermis or subcutaneous layer
– Various connective tissues that separate the skin from other organs
ie: muscles and bones
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Skin Functions
• 1. Temperature• 2. Sensory• 3. Moisture Control• 4. Protection
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Skin Functions
1. Protection – separate inside from outside2. Excretion salts, water, wastes3. Maintenance body temperature4. Produce melanin5. Produce keratin6. Synthesize vitamin D7. Store lipids and various fat cells8. Detect sensation touch, pressure, pain,
temperature
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The Epidermis
• Upper skin surface• Protective, keeps micro-organisms out• Avascular
– Having no blood cells
Made up mostly of keratinocytes (contain large amounts of proteins)
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Thick skin vs. Thin skin
Thin Skin• Covers most of the body• Has 4 layers• About the thickness of a
plastic sandwich baggie
Thick Skin• Found on the palms and
soles of feet• And the soles of your feet• Contains an extra layer
• About the thickness of a paper towel
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Layers of the Skin
• Stratum Germinativum• Major layer of the skin containing multiple
different cell types
Basal CellsMelanocytesMerkel Cells
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Basal Cells – stem cells that become keratinocytes
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Melanocytes – produce melanin (skin pigments responsible for skin tone)
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Merkel Cells – Sensitive to touch
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The other skin layers . . .
1. Stratum spinosum2. Stratum granulosum3. Stratum lucidum4. Stratum corneum
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Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum germinativumor Stratum basale
Dermis
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The Life of Skin
• Cells move from layer to layer• This process takes between 15-30 days
– Stratum germinatvum stratum corneum
• Last about two weeks before they are shed
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Skin Color
2 factors
1. Pigments found in the epidermis2. Circulation through the dermis
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Pigments
Carotene• Orange-yellow pigment• In fatty tissues• Tends to be more dominant
in light skinned individuals
Melanin• Brown, yellow, or black
pigment
• Aide in protection and use of UV radiation
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Dermal Circulation
• Blood flows through the dermis adding a pink hue to the skin
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Epidermal fun facts
When the blood supply to the skin is reduced, the skin turns pale.
Embarrassment usually causes a rush of blood to the surface blood vessels resulting in a flushed appearance.
Sustained circulatory reduction causes cyanosis - blue lips and fingernails. (caused by cold, heart attack, oxygen depletion).
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UV exposure causes melanocytes over-production (tan) and the production of vitamin D3 or cholecalciferol.
The liver converts this to a hormone called calcitriol which is necessary for normal Ca and P absorption in the small intestine.
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The Dermis
• Lies between the epidermis and subcutaneous
• Has capillaries, connective tissues, and glands• Sensory nerves
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a. Nociceptors
Fast pain—sharp (deep cut, needle) Slow pain—burning, aching, throbbing
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Thermoreceptors. Free nerve endings 3 - 4 x more cold receptors than warm
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Accessory Structures
I. Hair Nonliving—produced in follicles
- 98% on general body surface (not head)
- lose 50/day.
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• 3 types: lanugos (prenatal)
vellums (peach fuzz—most of the body)
terminal (heavy, usually deeply pigmented, head).
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Glands - two types of exocrine glands: Sebaceous & Sweat.
A. Sebaceous glands (oil glands). Secretes sebum
Sebum—inhibits bacterial growth, lubricates hair and skin.
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Sweat glandsApocrine sweat glands are found in the arm
pits, groin, nipples.
This secretion along with bacteria yields 2,3 hexonoic acid.
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Merocrine sweat glands are more numerous and more widely distribute.
Adults—2.5 million, high concentration in palms of hands.
Modified sweat glands: mammary glands - milk /ceremonious glands - ear wax
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Nails – dead, tightly compressed cells packed with keratin.
Protect exposed tips of fingers and toes.
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Review integumentary repair Review the integration of the integumentary
system with other systems Review burns and grafts
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Burns
• 1st Degree Burn• - superficial (involves the epidermis)
- painful, tender and swollen
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• 2nd Degree Burn• - partial thickness (involves the dermis and
above)- painful, discolored, blisters, oozing liquid
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• 3rd Degree Burn - full thickness burn (beyond the dermis) - not painful, charred(black), or white.