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 to measure possible damageBacterial damage – skin secretions are acidic and inhibit bacteria.Ultraviolet radiation – melanin produced to protect from UV damage
2 Skin Functions Thermal control – regulates body temperature Heat loss: sweat to cool the skinHeat retention: prevents blood to rush into capillary bedsWaterproofing – contains lipids to prevent drying outExcretion of waste – urea and uric acid secreted in sweatMakes vitamin D – modifies cholesterol molecules in skin and converts it to vitamin D
3 Skin Structure Epidermis — outer layer Dermis – middle layer made of stratified squamous epitheliumoften keratinized (hardened by presence of keratin)Dermis – middle layermade of dense connective tissueSubcutaneous tissue – deepest layeralso referred to as the ‘hypodermis’not considered part of the skin
4 Skin Structure Summary of layers from deepest to most superficial: Stratum basaleStratum spinosumStratum granulosumStratum lucidumStratum corneum
5 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.
6 Layers of the Epidermis Stratum basaleDeepest layer of epidermisCells actively undergoing cell divisionNew cells are pushed upward to become the more superficial layersStratum spinosum – intermediate layerStratum granulosum – another layer
7 Layers of the Epidermis 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 protective protein preventing water loss from skin
8 KeratinizationCells migrate to the epidermis where eventually they fall off.As they move upward, keratin is added.The cells in the epidermis contain a lot of keratin which resists damage.Distinct layers of cells are called strata.A cell takes ~ 40 – 56 days from creation to sloughing off
9 Melanin Pigment (melanin) produced by melanocytes Melanocytes are mostly in the stratum basaleColor is yellow to red to brown to blackAmount of melanin produced depends upon genetics and exposure to sunlight
10 Melanin continued….Large amounts of melanin occur in some regions like freckles, moles, and nipples.Less melanin occurs in the lips, hands, and soles of the feet.All races have the same number of melanoctyes! The amount of melanin produced is determined by genetics.
11 AlbinismA single mutation can cause a deficiency or complete absence of melanin.Albinos have fair skin, white hairs, and unpigmented eyes
12 What causes Normal Skin Color MelaninYellow, brown, or black pigmentsCaroteneOrange-yellow pigment from some vegetablesHemoglobinRed coloring from blood cells in dermal capillariesOxygen content determines the extent of red coloring
13 Dermis Two layers Papillary layer (upper dermal region) Projections called dermal papillaeSome contain capillary loops containing bloodSome pain receptors and touch receptorsReticular layer (deepest skin layer)Blood vesselsSweat and oil glandsDeep pressure receptors
14 Dermis Overall dermis structure Collagen and elastic fibers located throughout the dermisCollagen fibers give skin its toughnessElastic fibers give skin elasticityDermal papillae – extend toward the epidermis and deliver nutrients, remove waste products (sweat = urea and uric acid) and aid in regulating body temperature.