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integumentary system
first line of defense aainst a hostile environment - cutaneous membrane and accessory structures
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6 functions of skin and subcutaneous layer
- 1. protect
- 2. excrete
- 3. regulate temperature
- 4. synthesis of vitamin D3 5. storage of nutrients
- 6. touch sensation (pressure, pain, temperature)
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the epidermis consists of what type of epithelium?
stratified squamous
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the epidermis is:
a) vascular
b) avascular
- the epidermis is:
- a) vascular
- b) avascular - cells rely on the diffusion capillaries within the dermis
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thick skin
contains 5 layers found on the soles and palms
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thin skin
contains only 4 layers found everywhere except soles and palms
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skin color
a result of epidermal pigmentation
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carotene
can be converted to Vitamin A - yellow
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layers of the epidermis - in order from basal lamina to the free surface
- cells flatten and fill with the protein keratin as they rise to the surface:
- stratum germinativum
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
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stratum germinativum
aka basale - deepest epidermal layer, attached to the basmement mebrane (dermis
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fingerprints are formed by...
layers of the epidermis touching the ridges of the dermal papilla layer of the dermis
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basal cells
stem cells that are constantly dividing - part of the stratum germinativum
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merkel cells
function as touch sensitive receptors for the nervous system within the stratum germinativum layer of the epidermis
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melanocytes
produce melanin when stimulated by UV light
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stratum spinosum
superficial to the stratum germinativum (8-10 layers of cells)
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keratinocytes
produce keratin which is used for structure and water resistance
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langerhans cells
stimulate and assist the immune system upon penetration by pathogens
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stratum granulosum
3rd epidermal layer - where cells fill with keratin and die
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stratum lucidum
extra layer in thick skin - cells completely filled with keratin
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stratum corneum
exposed surface of both thick and thin skin, 15-300 layers of keratinized cells, protective barrier of dead, durable and expendable cells protecting underlying epidermal layers, constantly being sloughed or shed off (15-30 days to rise, stay for approximately 2 weeks)
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epidermal growth factor - 4 effects on epithelia
- 1. promote the divisions of germinative cells
- 2. increase the production of keratin
- 3. stimulate secretion by epithelial glands
- 4. stimulate epidermal repair after injury
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the dermis
contains blood vessels, glands, and accessory structures - lies between the epidermis and the subcutaneous layer
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2 major layers of the dermis
- 1. papillary layer
- 2. reticular layer
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papillary layer
composed of loose connective tissue - meissner's corpuscles
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reticular layer
composed of dense irregular connective tissue - pacinian corpuscles
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meissner's corpuscles
sensitive to light touch
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pacinian corpuscles
sensitive to deep pressure and vibration
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the subcutaneous layer consists of what types of tissues?
aka: hypodermis - consists of adipose and areolar tissues - very elastic
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3 types of accessory structures
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hair
approx. 5 million that have very little function (slightly insulate skin surface, provide UV protection, filter air the passes into/by the body surface)
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2 types of hair
- 1. vellus hair
- 2. terminal hair
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vellus hair
fine, lightly pigmented - covering the majority of the body surface
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terminal hair
thick, pimented - found on top of head, eyebrows, eyelashes
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scalp hair timing...
remains attached and growing for 2-5 years (average adult scalp loses approx. 50 hairs a day)
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hair color
determined by the type and amount of melanin produced by the follicle
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gray hair is a result of...
pigment production slowing with age - bubbles are produced in the medullary (middle layers)
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follicles
where hair originates - deep through the dermis and into the hypodermis terminating at the bulb
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arrector pili muscles
muscles associated with each hair root - can be pulled upright to cause goosebumps
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cuticle
hard, dead, keratinized cells that cover hairs
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cortex
contains hard keratin
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medulla
contains soft, flexible keratin
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4 types of glands
- 1. sebaceous (oil) glands
- 2. sudiferous/sweat glands
- 3. mammary glands
- 4. ceruminous glands
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sebaceous glands
oil glands - secrete sebum (waxy, oily substance) into the hair follicle by holocrine secretion - functions to keep hair and skin smooth and supple
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2 types of sudiferous/sweat glands
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apocrine sweat glands
located in pubic and axillary areas - begin to secrete sticky, cloudy, odor-producing secretions into hair follicles at puberty
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merocrine (eccrine) sweat glands
located over entire body surface, but highly concentrated on palms and soles - secrete sweat directly to skin surface
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mammary glands
modified apocrine glands whose secretions are highly regulated by ffemale sex hormones
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ceruminous glands
modified sweat glands that secrete cerumen (earwax) in external auditory canal
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nails
plates of keratin located on the dorsal ends of fingers and toes that protect digits from mechanical stress
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aging effects on the integumentary system
- Epidermis thins
- Vitamin D3 levels decrease by 75%
- Melanocyte activity declines, skin becomes pale
- Glandular activity declines
- Merocrine sweat glands are less active, older people cannot loose heat as fast as young people
- Blood supply to the dermis is reduced
- Hair follicles stop functioning or produce thinner, finer hairs, hair grays
- Dermis thins
- Secondary sexual characteristics fade
- Skin repairs proceed slowly, recurring infections may result.
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