Terms
Integumentary System |
Consists of the skin, hair, nails, and associated glands |
Dermatology |
Scientific study and medical treatment of the integumentary system |
Functions of the Skin
Resistance to trauma and infection |
Keratin - Acid mantle |
Other barrier functions |
Waterproofing, UV radiation, Harmful chemicals |
Vitamin D synthesis |
Skin first step, Liver and kidneys complete process |
Sensation |
Skin is our most extensive sense organ |
Thermoregulation |
Thermoreceptors, Vasoconstriction/vasodilation |
Nonverbal communication |
Acne, birthmark, or scar |
Transdermal absorption |
Administration of certain drugs steadily through thin skin via adhesive patches |
Epidermis |
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 |
Sweat Glands
Two kinds of sweat (sudoriferous) glands, Merocrine (eccrine) sweat glands |
– Apocrine sweat glands - Develop at puberty
• Bromhidrosis—disagreeable body odor produced by bacterial action on fatty acids
• Diaphoresis—sweating with wetness of the skin |
SEBACEOUS GLANDS
• Sebum—oily secretion produced by sebaceous glands |
CERUMINOUS GLANDS - only in external ear canal |
MAMMARY GLANDS —milk-producing glands that develop only during pregnancy and lactation |
SKIN COLOR
• 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 |
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 |
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 |
Hemoglobin—red pigment of red blood cells - Adds reddish to pinkish hue to skin |
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 |
Burns
–leading cause of accidental death
–Debridement: removal of eschar (burned tissue)
–Classified according to the depth of tissue involvement |
– First-degree burn: partial-thickness burn; involves only the epidermis
•Marked by redness, slight edema, and pain |
– Second-degree burn: partial-thickness burn; involves the epidermis and part of the dermis |
– 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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SKIN:
-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 |
Two Layers: Epidermis & Dermis |
• Epidermus- |
• 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 |
Hypodermis—another connective tissue layer below the dermis
–Subcutaneous tissue
–More areolar and adipose than dermis
–Pads body
–Binds skin to underlying tissues |
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 |
Thin Skin- covers rest of the body - Epidermis about 0.1 mm thick - Possesses hair follicles, sebaceous glands, and sweat glands |
Five Types of Cells of the Epidermis
Stem Cells |
Undifferentiated cells that give rise to keratinocytes
In deepest layer of epidermis (stratum basale) |
Keratinocytes |
Majority of epidermal cells
Synthesize keratin
very tough protein |
Melanocytes |
Occur only in Stratum Basale
Synthesize pigment melanin that shields DNA from ultraviolet radiation
melanin accumulates in the keratinocytes |
Tactile Cells |
receptors for touch |
Dendritic Cells |
Macrophage (modified white blood cell)
originating in bone marrow that guard against pathogens
Guard against toxins, microbes, and other pathogens that penetrate skin |
The Life History of a Keratinocyte
Keratinocytes produced deep in the epidermis by stem cells in stratum Basale |
Mitosis requires an abundant supply of oxygen and nutrients |
Deep cells acquire oxygen from blood vessels in nearby dermis |
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 |
Calluses\corns—thick accumulations of dead keratinocytes on the hands or feet |
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 |
Cells above the water barrier quickly die |
-Barrier cuts them off from nutrients below |
-Dead cells exfoliate (dander)
Dandruff: clumps of dander stuck together by sebum (oil) |
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Colors of Diagnostic Value
Cyanosis |
blueness of the skin |
Erythema |
abnormal redness of the skin |
Pallor |
pale or ashen color |
Albinism |
genetic lack of melanin that results in white hair, pale skin, and pink eyes - Have inherited recessive, nonfunctional tyrosinase allele |
Jaundice |
yellowing of skin |
Hematoma (Bruise) |
mass of clotted blood showing through skin |
Hair & Nails
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 |
Hair: Pilus
• Pilus— Hair —a slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle |
• 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 |
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 |
• Hair receptors – goosebumps - Piloerector muscle (arrector pili) |
– Extends from dermal collagen to connective tissue root sheath Hair Texture and Color |
• 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 |
Three types of skin cancer
• 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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