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Integumentary System
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Consists of the skin, hair, nails, and associated glands
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Dermatology
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Scientific study and medical treatment of the integumentary system
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Resistance to trauma and infection
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Keratin - Acid mantle
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Other barrier functions
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Waterproofing, UV radiation, Harmful chemicals
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Vitamin D synthesis
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Skin first step, Liver and kidneys complete process
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Sensation
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Skin is our most extensive sense organ
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Thermoregulation
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Thermoreceptors, Vasoconstriction/vasodilation
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Nonverbal communication
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Acne, birthmark, or scar
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Transdermal absorption
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Administration of certain drugs steadily through thin skin via adhesive patches
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Epidermis
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Keratinized stratified squamous epithelium
-Dead cells at the surface packed with tough protein called keratin -Lacks blood vessels -Depends on the diffusion of nutrients from underlying connective tissue -Sparse nerve endings for touch and pain |
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Two kinds of sweat (sudoriferous) glands, Merocrine (eccrine) sweat glands
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– Apocrine sweat glands - Develop at puberty
• Bromhidrosis—disagreeable body odor produced by bacterial action on fatty acids • Diaphoresis—sweating with wetness of the skin |
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SEBACEOUS GLANDS
• Sebum—oily secretion produced by sebaceous glands |
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CERUMINOUS GLANDS - only in external ear canal
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MAMMARY GLANDS —milk-producing glands that develop only during pregnancy and lactation
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• Melanin—most significant factor in skin color
-Produced by melanocytes released by exocytosis -Accumulate in the keratinocytes -Eumelanin—brownish black -Pheomelanin—a reddish yellow sulfur-containing pigment -People of different skin colors have the same number of melanocytes |
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Dark-skinned people
-Produce greater quantities of melanin -Melanin granules in keratinocytes more spread out than tightly clumped -Melanin breaks down more slowly -Melanized cells seen throughout the epidermis |
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Light-skinned people
-Melanin clumped near keratinocyte nucleus -Melanin breaks down more rapidly -Little seen beyond stratum basale -Amount of melanin also varies with exposure to (UV) rays of sunlight |
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Hemoglobin—red pigment of red blood cells - Adds reddish to pinkish hue to skin
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Carotene—yellow pigment acquired from egg yolks and yellow/orange vegetables will turn skin yellow if consumed in large quantities. - Concentrates in stratum corneum and subcutaneous fat
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–leading cause of accidental death
–Debridement: removal of eschar (burned tissue) –Classified according to the depth of tissue involvement |
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– First-degree burn: partial-thickness burn; involves only the epidermis
•Marked by redness, slight edema, and pain |
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– Second-degree burn: partial-thickness burn; involves the epidermis and part of the dermis
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– Third-degree burn: full-thickness burn; the epidermis and all of the dermis, and often some deeper tissues (muscles or bones) are destroyed
•Often requires skin grafts •Needs fluid replacement and infection control |
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-The body’s largest and heaviest organ
–Covers area of 1.5 to 2.0 m2 –15% of body weight –Most skin is 1 to 2 mm thick |
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Two Layers: Epidermis & Dermis
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• Epidermus-
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• Dermis—connective tissue layer beneath the epidermis
–Ranges from 0.2 mm (eyelids) to 4 mm (palms, soles) –Composed mainly of collagen with elastic fibers, reticular fibers, and fibroblasts –Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings |
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Hypodermis—another connective tissue layer below the dermis
–Subcutaneous tissue –More areolar and adipose than dermis –Pads body –Binds skin to underlying tissues |
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Thick skin— on palms and sole, and corresponding surfaces on fingers and toes - Has sweat glands, but no hair follicles or sebaceous (oil) glands - Epidermis 0.5 mm thick
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Thin Skin- covers rest of the body - Epidermis about 0.1 mm thick - Possesses hair follicles, sebaceous glands, and sweat glands
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Stem Cells
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Undifferentiated cells that give rise to keratinocytes
In deepest layer of epidermis (stratum basale) |
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Keratinocytes
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Majority of epidermal cells
Synthesize keratin very tough protein |
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Melanocytes
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Occur only in Stratum Basale
Synthesize pigment melanin that shields DNA from ultraviolet radiation melanin accumulates in the keratinocytes |
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Tactile Cells
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receptors for touch
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Dendritic Cells
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Macrophage (modified white blood cell)
originating in bone marrow that guard against pathogens Guard against toxins, microbes, and other pathogens that penetrate skin |
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Keratinocytes produced deep in the epidermis by stem cells in stratum Basale
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Mitosis requires an abundant supply of oxygen and nutrients
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Deep cells acquire oxygen from blood vessels in nearby dermis
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Newly formed keratinocytes push the older ones toward the surface
-In 30 to 40 days a keratinocyte makes its way to the skin surface and flakes off -Slower in old age - Faster in injured or stressed skin |
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Calluses\corns—thick accumulations of dead keratinocytes on the hands or feet
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Waterproofing is Achieved By:
-Lipids secreted by keratinocytes -Tight junctions between keratinocytes- thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes -Critical to retaining water in the body and preventing dehydration |
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Cells above the water barrier quickly die
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-Barrier cuts them off from nutrients below
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-Dead cells exfoliate (dander)
Dandruff: clumps of dander stuck together by sebum (oil) |
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Cyanosis
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blueness of the skin
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Erythema
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abnormal redness of the skin
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Pallor
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pale or ashen color
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Albinism
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genetic lack of melanin that results in white hair, pale skin, and pink eyes - Have inherited recessive, nonfunctional tyrosinase allele
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Jaundice
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yellowing of skin
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Hematoma (Bruise)
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mass of clotted blood showing through skin
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Hair/nails are made of mostly dead, keratinized cells
-Pliable soft keratin makes up stratum corneum of skin -Compact hard keratin makes up hair and nails -Tougher and more compact due to numerous cross-linkages between keratin molecules |
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• Pilus— Hair —a slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle
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• Three kinds of hair grow over the course of our lives
-Lanugo: fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development not all infants are born with lanugo -Vellus: fine, pale hair that replaces lanugo by time of birth -Terminal: longer, coarser, and usually more heavily pigmented |
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Hair is divisible into three zones along its length
Bulb: a swelling at the base where hair originates in dermis or hypodermis - Only living hair cells are in or near bulb Root: the remainder of the hair in the follicle Shaft: the portion above the skin surface |
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• Hair receptors – goosebumps - Piloerector muscle (arrector pili)
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– Extends from dermal collagen to connective tissue root sheath Hair Texture and Color
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• Texture—related to differences in cross-sectional shape
– Straight hair: round - Wavy: hair oval Curly hair: relatively flat Color—due to pigment granules in the cells of the cortex –Brown & black hair rich in eumelanin – Red hair high concentration of pheomelanin – Blond hair has an intermediate amount of pheomelanin and very little eumelanin – Gray and white hair results from scarcity or absence of melanin in the cortex and the presence of air in the medulla -Testosterone causes terminal hair in scalp to be replaced by vellus hair -Hirsutism—excessive or undesirable hairiness in areas that are not usually hairy |
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• named for the epidermal cells in which they originate
-Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma -Person with metastatic melanoma lives only 6 months from diagnosis, 5% to 14% survive 5 years |
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