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SKIN FUNCTIONS: PROTECTION FROM UNDERLYING TISSUES forms the first line of defense and a protective barrier against microbes: secretions from oil glands are acidic and sweat glands are salty, waterproofing due to the protein keratin, thick stratum corneum prevents bacteria from traveling to dermis where blood vessels are found Langerhans cells in the epidermis SKIN FUNCTIONS: VASOCONSTRICTION decreased flow of blood to the area to prevent heat loss SKIN FUNCTIONS: VASODIALATION increased flow of blood to the area for cooling SKIN FUNCTIONS: COOLING muscles shiver involuntary to produce heat, arrector pili muscle contracts, hairs stand on end, supression of sweating, vasoconstriction SKIN FUNCTIONS: HEATING sweat glands activate, vasodialiation, evaporate cooling of sweat SKIN FUNCTIONS: VITAMIN D PRODUCTION made by cells in the skin upon sun exposure and transported to the liver and kidneys where it is converted to a hormone called calcitriol that regulates calcium and phosphorus metabolism in the body SENSORY RECEPTORS temperature, touch, and pain SENSORY RECEPTORS detect touch, pressure, pain, hot and cold SENSORY RECEPTORS: TACTILE (MERKEL DISCS, MESSINER CORPUSCLES) fine touch, pressure, and vibration receptors SENSORY RECEPTORS: LAMELLATED CORPUSCLES (PACINIAN) deep pressure receptors SENSORY RECEPTORS: RUFFINI CORPUSCLES pressure and distortion of the skin reception MELANIN is brown-black pigment produced by melanocytes in stratum basale. Produce vesicles of melanin in melanosomes (larger vesicles in darker skin). Melanocytes respond to UV by ↑ production of melanin KERATIN made by keratinocytes, provides a waterproofing for the skin STRATUM CORNEUM the most superficial layer, composed of 15-30 layers of dead keratin-filled cells that can flake off as dandruff or form a callus or corn, serves as a protection again microbes, assisted by sebaceous glands (oil glands), & cells remain at this layer for about 2 weeks before being shed or washed away STRATUM LUCIDUM only found in thick skin such as palms/soles. * Not in all skin STRATUM GRANULOSUM thin layer of about 3-5 layers of keratinocytes, cells have usually stopped dividing by the time they reach this layer and started making large amounts of keratin STRATUM SPINOSUM forms keratin and consists of 8-10 layers of keratinocytes and Langerhans cells, cells in this layer are held together by desmosomes, interconnections between cells that held them to withstand mechanical stress STRATUM BASALE the deepest layer. This layer contains stem cells to replace keratinocytes at the epithelial surface. Skin surfaces that lack hair also contain specialized epithelial cells known as Merkel cells. It takes 15-30 days for cells to move from this layer to the stratum corneum TIGHT (OCCLUDING) JUNCTIONS form an impermeable barrier to the passage of fluids GAP (COMMUNICATING) JUNCTIONS connection between cytoplasm for ions/molecules to flow, form the intercalated discs of the heart DESMOSOMES structure used to adhere types of squamous ET together (prevents stresses), & account for the reason our skin peels off in sheets DERMIS the deeper and thicker layer of the skin PAPILLARY LAYER most superficial, deep to the stratum basale, composed of loose areolar ct, dermal papillae, sensory nerve fibers, & blood vessels PAPILLARY: DERMIS: DERMAL PAPILLAE found in the upper portions of the dermis, these papillae project into and anchor the epidermis, overlying epidermis, they form epidermal ridges (fingerprints) to increase friction and provide a better gripping surface, (think "egg crate" appearance) RETICULAR LAYER deeper, dense irregular ct, & collagen and elastin fibers (strength) LINES OF CLEAVAGE follow the bundles of fibers in the skin, cuts parallel to a line of cleavage heal with little scarring while cuts perpendicular to the line of cleavage result in greater scarring HAIR LOCATION located on all body parts except for palms of hands and soles of feet, and some parts of genitalia HAIR STRUCTURE projects from hair follicle located in the dermis of the skin, VELLUS HAIRS fine "peach fuzz" hairs found on much of the body's surface TERMINAL HAIRS heavy, more pigmented, and sometimes curly. Head hairs, eyebrows, eyelashes. . . HAIR SHAFT the portion that extends beyond the skin HAIR ROOT the portion located within the follicle NAILS located at the distal ends of phalanges (fingers and toes), & composed of keratin; the cuticle is a fold of skin that hides the nail root SUDORIFEROUS GLANDS produce sweat and are present in all regions of skin, open into hair follicles in the anal region, groin, and armpits, & develop at puberty; activate under stress SEBACEOUS GLANDS produce oil (sebum) ALBINISM occurs when melanocytes are incapable of producing melanin FRECKLES small pigmented areas with irregular borders VITILIGO occurs when people lose their melanocytes; spotty skin pigmentation CYANOSIS occurs when oxygen is released from hemoglobin and the color is dark red, the skin (such as lips, underneath fingernails) appears blue from the surface, & indicates cold or cardiovascular/respiratory disorders ERYTHEMA a red blood cell pigment that is bright red when bound to oxygen and gives the skin a reddish tone when the skin is hot and flushed (hemoglobin) LIVER SPOTS (SENILE LENTIGO) develop with age on sun-exposed skin; they have regular borders JAUNDICE yellow skin coloring caused by liver problems BRONZING (ADDISON'S DISEASE) a problem associated with adrenal gland disorders FIRST DEGREE BURNS epidermis only is burned, erythemia and brief pain, & minor sunburn can cause 1st degree burns SECOND DEGREE BURNS epidermis and superficial dermis, blisters, erythemia, pain, & heals with minimal scarring THIRD DEGREE BURNS epidermis and dermis, blackened or reddened with no pain, & skin grafts and IV fluid are needed FOURTH DEGREE BURNS burns penetrate muscles and other organs BURNS result in fluid loss, which leads to electrolyte imbalance (treatment-IV fluid), loss of protective covering, (treatment-sterile padding), protein denaturation and cell death, (treatment-IV drip with a high protein diet) RULE OF NINES anterior arms - 4.5%, posterior arms - 4.5% (each arm is a total of 9% each), & anterior legs - 9%, posterior legs - 9% (each leg is a total of 18% each) CANCER when cells undergo uncontrolled growth and are not regulated by signals involved with controlling the cell cycle, & involve mutations in DNA CANCER: NORMAL CELLS undergo cell cycle 50 times then die through programmed cell death CANCER CELLS undergo cell cycle repeatedly and do not die, & they don't undergo the cell cycle more rapidly, they do not die after 50 mitotic events BASAL CELL CARCINOMA least dangerous but most common; starts in stratum basale, rarely malignant, but it does metastasize to surrounding tissues CARCINOMAS occur in epithelial tissues; includes melanomas (most dangerous form of skin cancer), & include skin cancer, breast cancer, colon cancer, etc ADENOCARCINOMAS cancers of glandular epithelial tissues (such as salivary gland cancer) SARCOMAS cancers of muscles, connective tissues (such as bone cancer) LYMPHOMAS cancers of lymphoid tissues (such as tonsil cancer) LEUKEMIAS cancers of the blood SQUAMOUS CELL CARCINOMA the second most common type of skin cancer; usually forms due to sun exposure, occurs in the keratinocytes of the stratum spinosum, lung cancer, penis and cervix cancer, and esophagus cancer usually are this type MELANOMA a malignant tumor of melanocytes, less common than other skin cancers but responsible for most of the deaths, the most dangerous form of skin cancer, & to detect melanomas, remember the ABCDE rule ABCDE RULE asymmetrical skin lesion, border of the lesion is irregular, color: melanomas usually have multiple colors, diameter: moles greater than 6 mm are more likely to be melanomas than smaller moles, & enlarging or evolving REPAIR fibroblasts form a network of collagen fibers to stabilize the site which forms a framework SCAR TISSUE mostly collagen fibers, the tissue is remodeled when cells migrate to the site to complete the regeneration of the tissue