structure of the skin dermis –sometimes called “true skin”—much thicker than the epidermis...
TRANSCRIPT
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Structure of the Skin
• Dermis– Sometimes called “true skin”—much thicker
than the epidermis and lies beneath it– Gives strength to the skin– Serves as a reservoir area for storage of
water and electrolytes
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Structure of the Skin
• Dermis
• Contains various structures:• Arrector pili muscles and hair follicles • Sensory receptors • Sweat and sebaceous glands• Blood vessels
– Rich vascular supply plays a critical role in temperature regulation
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Structure of the Skin
• Dermis– Layers of dermis:
• Papillary layer—composed of dermal papillae that project into the epidermis; contains fine collagenous and elastic fibers; contains the dermal-epidermal junction; forms a unique pattern that gives individual fingerprints
• Reticular layer—contains dense, interlacing white collagenous fibers and elastic fibers to make the skin tough yet stretchable; when processed from animal skin, produces leather
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Structure of the Skin
• Dermis– Dermal growth and repair
• The dermis does not continually shed and regenerate itself as does the epidermis
• During wound healing, the fibroblasts begin forming an unusually dense mass of new connective fibers; if not replaced by normal tissue, this mass remains a scar
• Cleavage lines (Figure 6-6)—patterns formed by the collagenous fibers of the reticular layer of the dermis; also called Langer’s lines
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Structure of the Skin
• Hypodermis – Also called subcutaneous layer or superficial
fascia– Deep to the dermis, forming connection
between the skin and other structures– Not part of the skin
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Skin Color
• Melanin– Basic determinant of skin color is quantity,
type, and distribution of melanin– Types of melanin
• Eumelanin—group of dark brown (almost black) melanins
• Pheomelanin—group of reddish and orange melanins
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Skin Color
• Melanin (cont.)– Melanin formed from tyrosine by melanocytes
(Figure 6-7)• Melanocytes release melanin in packets called
melanosomes• Melanosomes are ingested by surrounding
keratinocytes and form a cap over the nucleus
– Albinism—congenital absence of melanin
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Skin Color
• Other pigments– Beta carotene (group of yellowish pigments from food)
can also contribute to skin color– Hemoglobin—color changes also occur as a result of
changes in blood flow • Redder skin color when blood flow to skin increases• Cyanosis—bluish color caused by darkening of
hemoglobin when it loses oxygen and gains carbon dioxide
• Bruising can cause a rainbow of different colors to appear in the skin
• Jaundice
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Functions of the Skin (Table 6-2)
• Protection– Physical barrier to microorganisms– Barrier to chemical hazards– Reduces potential for mechanical trauma– Prevents dehydration– Protects (via melanin) excess UV exposure
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Functions of the Skin
• Protection (cont.)– Surface film
• Emulsified protective barrier formed by mixing of residue and secretions of sweat and sebaceous glands with sloughed epithelial cells from skin surface; shedding of epithelial elements is called desquamation
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Functions of the Skin
– Surface film• Functions
– Antibacterial, antifungal activity– Lubrication– Hydration of skin surface– Buffer of caustic irritants– Blockade of toxic agents
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Functions of the Skin
– Surface film
– Chemical composition– From epithelial elements—amino acids, sterols,
and complex phospholipids– From sebum—fatty acids, triglycerides, and
waxes– From sweat—water and ammonia, urea, and
lactic acid and uric acid
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Functions of the Skin
• Sensation– Skin acts as a sophisticated sense organ– Somatic sensory receptors detect stimuli that
permit us to detect pressure, touch, temperature, pain, and other general sensations