4Integumentary Function ProtectionTemperature maintenanceSynthesis and storage of nutrientsSensory receptionExcretion and secretion
5Epidermis Avascular & Keratinized Thick skin – 5 layers Thin skin – 4 layersNew epidermis every daysCells:Keratinocytes (most cells) – produce keratinTightly connected by desmosomesCallus – accelerated keratin formationMelanocytes – (spider shaped) produce melaninMelanin taken in by keratinocytesShields nucleus from UVMerkel cells – sense skin curvatureLangerhans’ cells – star shaped phagocytes
6Layers of Epidermis Layers (starting from basement membrane): Stratum Germinativum (Basale)3 Intermediate layersStratum SpinosumStratum GranulosumStratum Lucidum**Stratum Corneum (superficial)
7Stratum Germinativum (aka stratum basal) Newly synthesized keratinocytes attached to basement by hemi-desmosomesForms ridge contours at interface of epidermal ridges and papillae of underlying dermisRidge contours are developmentally determined and visible in palmer, plantar, and digits1 layer of Stem cells or germinative cells dominate the stratum germintivumUndergoing mitosis10-25% melanocytes, some merkel cellsReceives nourishment from dermis
9Psoriasis Very common between 15-35 Autoimmune disease increased rate of mitosis despite same rate of sheddingNon-contagiousTreated w/topically or phototherapy
10Intermediate Strata Stratum Spinosum spiny or prickly layer Newly synthesized keratinocytes (several layers)Cells continue to divideLangerhans cells abundantStratum Granulosum3-5 flattened grainy cell layersStopped dividing, nuclei 7 organelles break downProduce keratin (durable, water resistant protein)Produce glycolipids –reduces water lossStratum LucidumThin layer clear layerFound in thick skin Densely packed cells filled with keratin
11Stratum Corneum Most Superficial layer ¾ of epidermis 20-30 layers of flat dead keratinized or cornified cellsHeld tightly together by desmosomesRelatively dry (prevents microorganism growth)Lasts about 2 weeks before shedAvg person sheds 40lbs of skin in a lifetime!
12Pigmentation: Skin Color Melanin (yellow, brown or black pigment)Produced by melanocytes in epidermisProduction increases in response to sun exposurePrevents skin damage by absorbing UV raysAll humans have same number of melanocytesFreckles & moles are areas of heavy melanin productionCarotene (orange-yellow pigment)Converted to vitamin A for epithelial maintenanceAccumulates in stratum corneumDermal CirculationOxygenated Hemoglobin - reddish tintConstricted blood vessels – paleCyanosis – Sustained constriction bluish color in Caucasian, only visible in nail beds of dark skin
13What causes the appearance of wrinkled, leathery skin?
14Sun Exposure UV stimulates production of vitamin D3 D3 is modified by liver and converted to calcitrol by kidneysCalcitrol essential for absorption of calcium and phosphorusToo much UV clumps elastin fibers causing leathery appearanceUV destroys folate needed for DNA synthesisToo much UV can also cause chromosomal damage in stem cells of stratum germinativum causing skin cancer
15Skin Cancer Most common form of cancer (and most preventable) Basal Cell Carcinoma – originates in stratum germanitivumSquamous Cell Carcinomas – superficial layersMalignant MelanomasExtremely dangerousBegins as a moleMelanocytes grow rapidly and metastasize through lymphatic systemKnow the ABCD rule!
16Do Now: What are Stretch Marks? Damage to the dermis (collagen & elastin fibers) due to rapid stretching of the skin due to rapid growth or weight gainAppear reddish- purple at first then fade to a lighter color over timeTend to occur in regions of the body where fat is storedHormonal changes, genetics, and diet can all affect development of stretch marks
17Dermis “hide” Striae – stretch marks Blisters Dermis – contains network of blood vessels, lymph vessels, and nerve fibersPapillary Layer (thin superficial)Loose connective tissuefibroblasts., macrphages, mast cellsDermal Papillae indent epidermisSupports and nourishes epidermisCapillaries and nervesMeissners corpsucles – touch receptorsReticular Layer (80% of dermis)Meshwork of dense irregular connective tissueElastic fibers provide stretch & recoilCollagen fibers provide rigidity & strengthBV, sweat and oil glandsPhagocytesStriae – stretch marksBlisters
21What causes a decubitus ulcer or bed sore? Caused by an interruption of blood supply to a tissue causing necrosis. These develop in patients that have been bed ridden for long periods of time. They are caused by the weight of the body on the skin overlying a bony area compressing the blood supply.
22Do Now: List & describe layers of the Integument EpidermisStratum corneumStratum lucidumStratum granulosumStratum spinosumStratum germanitivum (Basale)DermisPapillary LayerReticular LayerHypodermis
23Subcutaneous Layer Not actually part of integument, blurred boundary Anchors skin to muscles, but loosely so it can slideLoose connective tissue with many adipocytesFat distribution changes as grow and mature (shock absorption & insulation)Females thighs & breastsMales abdomen “beer belly”Contains no vital organs and few capillariesSubcutaneous injection useful method of administering drugs with hypodermic needle
24Accessory Structures: Hair and Hair Follicles 2.5 million hairs on human body!!Hair Growth CycleHair grows for 2-5 years about .3mm per day then pushed to surface to be shed for new cycle to begin (scalp 6-10 yr cycle, eyebrows 3-4 months)FunctionProtect scalp from UV, cushion head, and insulate skullPrevent entry of foreign particles in nostrils, ears, and eyesRespond to stress or cold (arrector pili smooth muscle in dermis forces hair to stand up)StructureWalls of follicle contain cells of epidermisHair Papilla – peg of connective tissue containing capillaries and nerves, cell division occursHair Root – anchors hair in to skinHair Shaft – 3 layers of dead keratinized cellsMedulla – core of hair (soft keratin)Absent in fine hairCortex – surrounds medulla (hard keratin)Cuticle – surface single layer made of overlapping shingles of cells
25Hair Texture Oval – silky & wavy Flat & ribbonlike – curly Round – straightConditioners – smooth out rough cuticles making it shinySplit ends – cuticle wears away at ends
26Hair Types: Cuticle Coronal Crown like (stacked paper cups) Small rodents & batsSpinousPetal or triangular shapedMink, cats and sealsImbricateFlattened, overlapping scalesHumans and other animalsMedullaFragmentary (trace)Discontinuous (broken)ContinuousCortexHuman pigment granules distributed by cuticle (except red-hair)Cattle, dogs and some humans have ovoid bodies
27Human Hairs vs. AnimalsConsistent color & pigmentation throughout shaft (see banding in animals)Animal pigmentation is centrally locatedHumans 2 types of hair:Vellus hair – fine body hairTerminal hair – coarser, darker hair (increased testosterone increases growth)
28Hair ColorGenetically determined by type and amount of pigment produced by melanocytesBrown – true melaninBlond - sulfurRed - ironGray - Pigment production decreasesWhite air bubbles within hair shaft
29Do Now: What is alopecia? Hairs not replaced as fast as they are shed, begins anteriorly and progresses posteriorlyMale pattern baldness – sex linked trait by delayed action gene that when turned on changes response to testosteroneUntil recently, only cure inhibits testosterone production
30What are comedones?Acne is caused by blocked sebaceous duct, forming a sebum plugAffects over 85% of adolescents and young adults.Secretions accumulate causing inflammation and possible bacteria infectionBlackheads – open comedones, melanin oxidizes turning blackWhiteheads – closed comedonesHormonal changes can cause increased oil productionTry not to squeeze, scratch, pick, or rub the pimples. Although it might be tempting to do this, it can lead to skin infections and scarring.
31Accessory Organs: Nails Protect exposed finger tips and limit distortion when exposed to mechanical stressTools – pick up or scratch itchFree EdgeNail body – dead keratinized cellsNail bed – epidermis covered by nail bodyNail root – anchors nail bodyNail matrix – nail growth occursCuticle – portion of stratum corneum extending over nailLunula – pale crescent (area of obscured blood vessels)
32Accessory Structures: Sebaceous Glands Holocrine oil glandsArrector pili muscle contracts squeezes the sebaceous gland forcing oily secretion outSebum (oily secretion) lubricates hair and skin and inhibits bacteria growth, slows water loss from skinGlands are sensitive to androgens (sex hormones)Cradle Cap – overactive sebaceous glands
33Accessory Structures: Sudoriferous (sweat) Glands About 3 million per person!Merocrine (eccrine) Sweat GlandsSecreted directly onto surface of skin via exocytosis99% water w/electrolytes, vitamin C, antibodies, metabolic wastes and drugs, pH of 4-6Cools surface of skin and lowers body tempToo much perspiration may lead to dehydrationFlushes microorganisms from surfaceApocrine Sweat Glandssweat glands that secrete products into hair follicles in armpits, nipples, and groinSticky, cloudy secretion released at pubertyOdorous as bacteria break it down as food
35Injury and Repair of Skin Inflammatory response – triggered by mast cells increase blood flow to areaScab (fibrin proteins) forms at surface to restrict entry of microorganismsCells divide rapidly to replace missing cellsMacrophages and phagocytes clear debris and patrol area for pathogensAnimation:Deeper woundsScar tissue – lots of collagen fibers and few blood vesselsFetuses don’t scarKeloid – thickened area of scar tissue with shiny smooth surface (tend to form in adults with dark skin)Damaged hair follicles, sebaceous and sweat glands, muscle cells and nerves are rarely repairedBurns1st degree – kills superficial epidermal cells, injures papillary dermis2nd degree – kills epidermis and possible some dermis, injures reticular dermis3rd degree – kills all epidermal and dermal cells, injures hypodermis and deeper tissuesSkin Gun:
37AgingEpidermis thins as stem cell activity decreases increasing skin injuries and infectionsNumber of macrophages and other immune system cells decreasesDecline in vitamin D3 production reduces calcium and phosphorus absorption weakening muscles and bonesMelanocyte activity decreases causing increases sensitivity to sunGland activity decreases causing dry scaly skinFollicles decrease function creating thin light hairElastic fibers decrease resulting in wrinklingReduced blood supply to dermis – less thermoregulationRepairs are slow…6-8 weeks
38Write an analogy for our skin…. Human skin is like __________ because _______________.
39Cardiovascular System Do Now:Integumentary SystemSkeletal SystemMuscular SystemNervous SystemEndocrine SystemCardiovascular SystemLymphatic SystemRespiratory SystemDigestive SystemUrinary SystemReproductive SystemComplete web showing how Integumentary system interconnected w/other organ systems!