Presentation on theme: "Seven Functions of Skin"— Presentation transcript:
1 Seven Functions of Skin Mechanical/Chemical damage – keratin toughens cells; fats cells cushion blows; and pressure receptors measure damageBacterial damage – skin secretions are acidic and inhibit bacteria.Ultraviolet radiation – melanin produced to protect from UV damage
2 Thermal control – regulates body temperature Heat loss: sweat to cool the skinHeat retention: prevents blood from losing heat & shiveringWaterproofing – contains lipids to prevent drying outExcretion of waste – urea and uric acid secreted in sweatMakes vitamin D – changes cholesterol molecules in skin and converts it to vitamin D
3 Skin Structure Epidermis — outer layer Dermis – middle layer Subcutaneous tissue – deepest layeralso referred to as the ‘hypodermis’
4 A cell takes 40 – 56 days from creation to sloughing off EpidermisSummary of layers from deepest to most superficial:Stratum basaleStratum spinosumStratum granulosumStratum lucidumStratum corneumA cell takes 40 – 56 days from creation to sloughing off
5 Layers of the Epidermis Stratum basaleDeepest layer of epidermisCells actively undergoing cell divisionNew cells push older cells upward until theyeventually fall offCells are mostly keratinocytes and some melanocytes
6 KeratinizationKeratin is a protein that helps harden skin cells, makes them tougher and helps prevent water loss by the body.Keratinocytes are responsible for making keratinKeratin makes the skin waterproofKeratin is found in cells of the basale and spinosum strata
7 Stratum spinosum – Made of keratinocytes Some cells grow projections that connect to other cells making the cell layer strongerPrickle Cells with long projectionsStratum granulosum – mostly flattened keratinocytes that have lost nuclei and organellesDeath zone of keratinocytes
8 Vitamin D Production Cells of stratum spinosum and basale: Vitamin D: UV energy + cholesterol = Vitamin DVitamin D:used by kidney to make the hormone calcitriolCalcitriol:necessary to signal small intestine to absorb calcium from the bloodNo Vitamin D no calcitriol no calcium absorption weak bones
9 Stratum lucidumFormed from dead cells of the deeper layersOccurs only in thick, hairless skin of the palms of hands and soles of feetStratum corneumOutermost layer of epidermisScale-like dead cells are filled with keratin which is a strengthening protein also preventing water loss from skin
11 Melanin Pigment (melanin) produced by melanocytes Melanocytes are mostly in the stratum basaleColor is yellow to red to brown to black
12 Melanocytes: Cells deep in the epidermis and dermis that produce a pigment called melanin which protects the cells from UV damageSkin color determined by the size and quantity of melanin granules in the tissue
13 What’s your color?Determined by genetic, environmental, and physiological factorsYour DNA determines how much MELANIN is producedUV radiation increases melanin productionCirculation, vitamin deficiencies, physical ailments (liver failure)
14 Why the Spots…?Large amounts of melanin occur in some regions like freckles, moles, and nipples.Caused by uneven distribution of melaninLess melanin occurs in the lips, hands, and soles of the feet.
15 AlbinismA single gene mutation can cause a deficiency or complete absence of melanin.Albinos have fair skin, white hairs, and unpigmented eyes (eyes appear red)
16 FingerprintsThe up and down border between the dermis and epidermis helps bond the layers togetherIn thick skin, epidermal ridges show on the surface as fingerprints:Function – enhance gripping
17 Dermis – the middle layer Papillary layer:Thin (20%)Consists:Contains dermal papillaeCapillaries, sensory neuronsFunction: feed epidermisReticular Layer:Thick (80%)Elastic and Collagen fibersSweat and oil glandsDeep pressure receptorsFunction: provide strength and flexibility
18 Dermal Papillaesmall, nipple-like extensions of the dermis into the epidermisBlood vessels nourish all hair follicles and bring nutrients and oxygen to the lower layers of epidermal cells
19 What makes us stay young looking? Elastic fibersgives skin elasticityfibers can stretch up to 1.5x their length and snap back to their original length when relaxedCollagen fibersgives skin support/firmness~ one quarter of the human body is collagensupport the skin’s mechanical strength and texture
20 Sensory Perception in Skin Skin is highly sensitivity to touch because of large amounts of sensory structures found in dermis
21 Sensory Perception in Dermis Merkel cells: deep layers of epidermissuperficial touchFree Nerve Endings: superficial dermispain and temperatureMeissner’s Corpuscles: superficial dermislight touchPacinian Corpuscles: deep dermis- pressure and vibrations
22 Skin Structure Subcutaneous tissue (hypodermis) is deep to dermis Not part of the skinAnchors skin to underlying organs, bones and musclesContains half of the body’s fat; acts as padding and insulation.
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