integumentary system skin, hair, nails, and glands

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INTEGUMENTARY SYSTEM

INTEGUMENTARY SYSTEMSkin, hair, nails, and glands

What does it mean?Integere (Latin)- to coverDermato and cutis (Greek and Latin)- skinEpi- (Greek)- upon or above

Why do we need it? overviewLargest organRetains moistureSensory receptors for:pain,HeatTouch Excretes saltsExcretes small amounts of wasteStores bloodRegulates body temp.2 main partsEpidermis and dermisUnder the dermis is the hypodermis (supericial fascia- subcutaneous tissue)It acts a foundation not truly part of the skin

EpidermisSurface skin1st line of defense against infectionContains no blood vesselsLayers and layers of epithelial cells

Melanocytes of stratum basale is made of theseSynthesize a pale yellow to black pigment called melaninCytocrine secretion- melanin is secreted into keratinocytesMelanin- skin color and protection against uv raysKeratinocytesmajority of stratum basalePrimary epithelial cell of skin

More about the epidermisCarotene- in stratum corneum and fatty layers beneath the skinProduces yellowish hue common with Asian ancestryHemoglobin- cause for pinkish color of Caucasian skinLess melanin, more hemoglobinAlbinos- no melanin in skin at allRidges and grooves- increase friction to grasp other objectsEx. Loops and whorls (fingerprints, palm prints, footprints)The DermisAlso known as the corium Thicker and more fibrous than the dermis2 layersFibrolasts- connective tissue developsMacrophages- engulf wastes and foreign microorganismsAdipose tissueThinnest over eyelids and male sex organsThicker on back than stomachThickest on palms of hands and soles of feetPapillary LayerTop (outer) layerSoftElastic, reticular fibers that enter the epidermis Brings blood and nerve endings closerPapillae are finger-like projections- loops of capillaries to increase the surface area of dermis and anchor epidermisMeissners corpuscles- nerve endings sensitive to soft touch.In some papillaeReticular LayerRete- net (Latin)Dense, irregular connective tissueInterlacing bundles of collagenous and elastic fibersStrong resistant layerGives skin strength, extensibility, ad elasticityOil glands (seaceous glands), sweat glands, fat cells, and larger blood vessels are in this layerHairFollicles embedded in the epidermis and extend to the dermis angle hair growth (curly or straight).Follicle bases are expanded (called bulbs) reach nerve endingsEpithelial cells in the bulb divide to create the hair shaft Hair pigment: melaninGives hair its colorGray and white hair grow when melanin levels decrease and air pockets formsebaceous gland- sebum is produced (cholesterol, fats, and other substances)Keeps hair soft, pliable, and waterproofHair has 3 layersMedullaCentral coreCells contain eleidin separated by air spacesFine hair- minimal/ nonexistentCortexMajor part of hair shaftSeveral layersFlattened cellsElongated pigment-bearing cells in dark hairAir pockets in white hairCuticleSingle layer, overlapping cells with free end pointing upStrengthens and compacts the inner layersSplit endsAbrasion wears away the end of the shaft, exposes the medulla and cortex to create the horrid split end

Sweat? Grossor is it?2 types of sweat glands (sudoriferous)Coiled tubules in the dermisEccrine glands-all over bodyWatery (99%), salty secretion known as sweatPasses through the epidermis to skins surface and opens to a sweat poreControlled by the sympathetic nervous systemApocrine sweat glandsUnder the armpits and groin area, associated with hair folliclesSame components as eccrine and is odorlessBacteria breaks down apocrine sweats fatty acids and proteinsCreates the odor accompanying post exercise

Connection to the Nervous System4 receptors are involved in the sensation of touch2 primary temperature receptorsDermis has neuromuscular spindles (proprioceptors)Transmit information to the spinal cord and brain about the lengths and tensions of musclesProvides awareness about the bodys position Spindles help in muscle coordination and muscle action efficiency Jess check with Hans but I think he covers this in his presentation!!!!!!Touch Free nerve endings- dendrites are primarily pain receptorsSometimes touch, temperature, and musclesFibers swell at the end in responseDisc-shaped (merkel discs) endings- light-touch receptors in deep layers of epidermisMeissners corpuscles- light-touch mechanoreceptors in dermal papillaeEgg-shaped capsules of connective tissue around a spiraled end of a dendriteGreat amounts in lips and fingertipsSense quick touch, not sustained

Pacinian corpuscles- deep-pressure mechanoreceptorDendrites surrounded by layers of connective tissueRespond to deep/firm pressure or vibrationVisible to the naked eye- 2 millimeters longHair nerve endingsRespond to change in hair positionBare dendritesTEMPERATUREEnd-bulbs of Krause (Krauses corpuscles)Activate below 68 degrees FBulbous capsule surrounds the dendriteCommonly found throughout the body in the dermis and lips, tongue, and conjunctiva of the eyesBrushes of Ruffini (Ruffini cylinders/Ruffinis Corpuscles)Respond between 77 degrees and 113 degrees FFound in dermis and subcutaneous tissueDendrite endings in flattened capsulesThere are less then end-bulbs and are deeper in the tissueHuman body is less sensitive to heat than to cold