解剖学英文皮肤Skin

The Integumentary System and Body Membranes,THE SKIN,Structure two primary layers called epidermis and dermisEpidermisOutermost and thinnest primary layer of skinComposed of several layers of stratified squamous epitheliumStratum germinativuminner layer of cells that continually reproduce; new cells move toward the surface As cells approach the surface, they are filled with a tough, waterproof protein called keratin; eventually cells flake offStratum corneum outermost layer of keratin-filled cells,THE SKIN,Skin pigmentdeepest epidermal layer is responsible for production of pigment, which gives color to the skinThe brown pigment melanin is produced by specialized cells in this layer (melanocytes)Dermal-epidermal junctionspecialized area between two skin layersBlisters can caused if this junction is damaged or destroyed,THE SKIN (cont.),DermisDeeper and thicker of the two primary skin layers and composed largely of connective tissueUpper papillary layer of dermis characterized by parallel rows of tiny bumps called dermal papillaeRidges and grooves in dermis form pattern unique to each individualBasis of fingerprintingImproves grip for tool use and walking,THE SKIN (cont.),DermisDeeper reticular layer of dermis : filled with network of tough, interlacing, collagenous and stretchable elastic fibersNumber of elastic fibers decreases with age and contributes to wrinkle formation Dermis also contains nerve endings, muscle fibers, hair follicles, sweat and sebaceous glands, and many blood vessels,THE SKIN (cont.),Accessory structures of the skinHair Soft hair of fetus and newborn is called lanugoHair growth requires epidermal tubelike structure called hair follicleHair growth begins from hair papillaHair root lies hidden in follicle and visible part of hair called shaftArrector pili specialized smooth muscle that produces “goose bumps” and causes hair to stand up straight,THE SKIN (cont.),Accessory structures of the skin (cont.)Receptors Specialized nerve endingsmake it possible for skin to act as a sense organTactile (Meissners) corpuscle /Merkel cellcapable of detecting light touchClose to the skin surfacePacini corpusclecapable of detecting pressureLocated deep in the dermisFree nerve endings painKrause end bulbs (bulboid corpuscles) low-frequency vibration,THE SKIN (cont.),Accessory structures of the skin (cont.)Nails Produced by epidermal cells over terminal ends of fingers and toesVisible part is called nail bodyRoot lies in a groove and is hidden by cuticleCrescent-shaped area nearest root is called lunulaNail bed may change color with change in blood flow,THE SKIN (cont.),Accessory structures of the skin (cont.)Skin glandsSweat or sudoriferousSebaceousSweat or sudoriferous glandsEccrine sweat glandsMost numerous, important, and widespread of the sweat glandsProduce perspiration or sweat, which flows out through pores on skin surfaceFunction through life and assist in body heat regulation,THE SKIN (cont.),Apocrine sweat glandsFound primarily in axilla and around genitaliaSecrete a thicker secretion quite different from eccrine perspirationBreakdown of secretion by skin bacteria produces odorSebaceous glandsSecrete oil or sebum for hair and skinLevel of secretion increases during adolescence Amount of secretion is regulated by sex hormonesSebum in sebaceous gland ducts may darken to form blackhead,THE SKIN (cont.),Skin cancer TypesSquamous cell carcinoma Basal cell carcinoma Malignant melanomaKaposi sarcomaCausesGenetic predispositionSuns ultraviolet (UV) radiation damages skin cell DNA, causing mistakes during mitosis,THE SKIN (cont.),Skin cancer (cont.)Basal cell carcinoma (most common type of skin cancer)Originates in cells at base of epidermisoften on upper faceLesions begin as small raised areas that erode in center, bleed, and crust overLess likely to metastasize than other skin cancer typesSquamous cell carcinomaCommon type of skin cancerSlow growingLesions begin as painless, hard, raised nodulesWill metastasize,THE SKIN (cont.),Skin cancer (cont.)Malignant melanomaMost serious form of skin cancerMay develop from benign, pigmented moles or excess UV radiationIncidence in the United States is increasingABCD rule of self-examination (Table 5-1)Kaposi sarcomaRare formFrequently associated with AIDS or immune deficiency,THE SKIN (cont.),Functions of the skin Protectionfirst line of defense against: Infection by microbesUltraviolet rays from sunHarmful chemicalsCuts and tearsTemperature regulationSkin can release almost 3000 calories of body heat per dayMechanisms of temperature regulation Regulation of sweat secretionRegulation of flow of blood close to the body surface,THE SKIN (cont.),Functions of the skin (cont.)Sense organ activitySkin functions as an enormous sense organReceptors serve as receivers for the body, keeping it informed of changes in its environment,THE SKIN (cont.),BurnsTreatment and recovery or survival depend on total area involved and severity or depth of the burnBody surface area is estimated using the “rule of nines” in adultsBody is divided into 11 areas of 9% eachAdditional 1% located around genitals,THE SKIN (cont.),Burns (cont.)Classification of burns First-degree (partial-thickness) burnsonly the surface layers of epidermis involvedSecond-degree (partial-thickness) burnsinvolve the deep epidermal layers and always cause injury to the upper layers of the dermis,THE SKIN (cont.),Burns (cont.)Third-deg