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chapter 5 (skin functions (physical barrier- water loss, injury, chemicals…
chapter 5
skin functions
physical barrier- water loss, injury, chemicals and microorganisms
chemical barrier- ph or 5-6, prevents microorganisms
biological barrier- Langerhans cells (epidermis), macrophages and mast cells (dermis)
EXCRETION
PROTECTION
minimal; mostly through kidneys
urea
uric acid
Light touch detection - meissners corpuscles egg shaped located in dermal papillae sensatiations
pressure detection- pacinian corpuscles onion shaped located in dermis and subcutaneous regions
5.9
vasodilation- increases dermal blood flow, which also increases heat loss
vasonstriction- decreases derma blood flow which decreases heat loss
radiation- most heat loss by this mode, infrared heat rays move this area of high heat to areas of low heat
conduction- less heat loss, heat moves by physical contact, the reason your seat is warm when you stand up
convection- heat loss to surrounding air, increases as air movement increases, that is why turning on a fan cool down your body
evaporation- heat loss varies, if heat increases our sweating increases, so we lost more heat by evaporating the sweat on the surface of the skin
hyperthermia- elevated body temp. 2 common causes= humid air decreases evaporation, air temp. exceeds body temp, thus heat is gained and not lost
hypothermia- low body temp. vert dangerous if core body temp. drops below 94 F, limbs can withstand about 65 F because they contain no vital organs
5.1 epidermis
stratum corneum- outer most layer, composed of dead epithelial tissue filled with keratin
stratum luciolum- translucent layer separating corneum and granulosum
stratum granulosum- composed of 3 to 5 layers of flattened granular cells (filled with keratin granules)
stratum spinosum- composed of many layers of spikey cells
stratum basale-innermost layer, directly above basement membrane
main function - protection
pigment= melanin (determines skin color and is produced by melanocytes in stratum basale)
5.3
vitamin D3
liver converts it into calcitriol
adds in absorption of calcium
weak and flexible bones without it
basal cell carcinoma - most common form of skin cancer, originates in stratum germinativum
squamous cell carcinoma- most superficial layer
malignant melanoma- dangerous, usually begins as a mole, metastasize through the lymphoid system
5.7
sebaceous glands- holocrine gland,associated with every hair follicle, secretion (holocrine)= sebum (i.e. oil)
skin glands- 2 types = merocrine (eccrine gland), aprocrine glands
merocrine glands= 2-5 million, coil deep in dermis,duct in dermis, pore at surface. Charateristics- respond to temp., no odor, function throughout life. Location- forehead, neck ,back
aprocrine glands- ducts terminate into hair follicles. Characteristics- respond to stress and emotion, odor in secretion, begin to function at puberty and throughout life. Location- armpits and groin
modified aprocrine glands
ceruminous glands- external ear, secretion = earwax
mammary glands- breasts; milk
5.8
nails
epithelium undergoing keratinization
functions= manipulation, protection
Structure= nail body covers nail bed
nail root- nail production by an epithelial fold
lunula- pale cresent near nail root
cuticle- fold of stratum corneum
5.2
people have same number of melanocytes but amount produced is determined by DNA
Environmental factors - UV rays, chemicals, and drugs
carotene may accumulate in s. corneum = orange
hemoglobin (HB)- in dermal blood vessels = pink
lack of hb in dermal blood vessels = blue (cyanosis)
inability to break down hb (liver problems) = yellow (jaundice)
5.6
hair follicles
structure- hair root (deep in dermis), hair shaft in epidermis, cuticle, cortex, medulla
keratinization- cells are in epithelium, cells in root= active mitosis, cells in follicle= maturing and accumulating keratin, cells in epidermis= dead epithelial cells, full of keratin
pigment- melanin decreases with age, genetically dertermined
hair papilla- peg of connective tissue, nerves and capillaries
arrector pilli muscle- a bundle of smooth muscle associated with every hair follicle
general structure
epidermis- outermost layer
dermis- inner layer
subcutaneous- distinct layer beneath skin also called hypodermis
5.4
dermis- inner layer of skin
2 distinct layers
papillary layer- 20% is below dermis, composed of areolar CT, surface forms dermal papillae (finger like projections into the epidermis), meissners corpuscles
reticular layer- 80%, dense irregular CT, bundles of collagen fibers, elastic fibers and reticular fibers that give the skin strength and resiliency
main function- nourishment of the epidermis
5.5
subcutaneous layer- beneath skin
Structure= adipose tissue and blood vessel
function= insulation