Nerve activates contraction

Chapter 4: Skin and Body Membranes20131

Hoban1Skin and Body MembranesFunction of body membranes: Cover body surfacesLine body cavitiesForm protective sheets around organs20132Types of Body MembranesEpithelial MembranesCutaneous membraneMucous membraneSerous membraneConnective Tissue MembranesSynovial membranes3Cutaneous MembraneCutaneous membrane = skinA dry membraneOutermost protective boundaryTwo major regions:Superficial epidermisConsists 0f keratinized stratified squamous epitheliumUnderlying dermis Mostly dense connective tissue4Figure 4.1a

Cutaneous membrane (the skin) covers the body surface.Cutaneousmembrane(skin)Mucous MembranesSurface epitheliumType depends on location:Stratified squamous epithelium (mouth, esophagus)Simple columnar epithelium (rest of digestive tract)Underlying loose connective tissue known as lamina propriaLines all body cavities that open to the exterior body surfaceOften adapted for absorption or secretion

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Mucosa ofnasal cavityMucosa ofmouthEsophagusliningMucosa oflung bronchi(b) Mucous membranes line body cavities open to the exterior.Serous MembranesSurface is a layer of simple squamous epitheliumUnderlying layer is a thin layer of areolar connective tissueLines open body cavities that are closed to the exterior of the bodySerous membranes occur in pairs, separated by serous fluidVisceral layer covers the outside of the organParietal layer lines a portion of the wall of ventral body cavity7Figure 4.1d

Outer balloon wall(comparable to parietal serosa)Air (comparable to serous cavity)Inner balloon wall(comparable to visceral serosa)(d) A fist thrust into a flaccid balloon demonstrates the relationship between the parietal and visceral serous membrane layers.Serous MembranesSpecific serous membranesPeritoneumAround the abdominal cavityPleuraAround the lungsPericardiumAround the heart9What is the meaning of peri?

ParietalperitoneumVisceralperitoneum(c) Serous membranes line body cavities closed to the exterior.ParietalpericardiumVisceralpericardiumParietalpleuraVisceralpleuraConnective Tissue MembraneSynovial membraneFound in connective tissue onlyLines fibrous capsules surrounding jointsSecretes a lubricating fluid to cushion and protect joint area2006Hoban 11Figure 4.2

2006Hoban 12Integumentary System Skin (cutaneous membrane)Skin derivativesSweat glandsOil glandsHairNails13

2006Hoban 14Skin Functions:Make sure you can explain (in your own words) HOW the skin completes each of the functions listed Refer to Table 4.1Checkpoint: Create an example that demonstrates each skin protection function15Skin StructureEpidermis outer layerStratified squamous epitheliumOften keratinized (hardened by keratin)DermisDense connective tissue

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Epidermis Dermis Connection17

Skin Structure:Subcutaneous tissue (hypodermis) is deep to dermisNot part of the skin!!!Function: Anchors skin to underlying organsComposed mostly of adipose tissue18Layers of EpidermisStratum basale (stratum germinativum)Deepest layer of epidermisLies next to dermisCells undergoing mitosisDaughter cells are pushed upward to become the more superficial layersStratum spinosumProtects against foreign materials and produces lipids that prevent moisture loss from the skin.Stratum granulosumThis layer helps prevent fluid loss from the body.

19Layers of EpidermisStratum lucidumFormed from dead cells of the deeper stataOccurs only in thick, hairless skin of the palms of hands and soles of feetStratum corneumOutermost layer of epidermisShingle-like dead cells are filled with keratin (protective protein prevents water loss from skin)20MelaninPigment (melanin) produced by melanocytesColor is yellow to brown to blackMelanocytes are mostly in the stratum basaleAmount of melanin produced depends upon genetics and exposure to sunlight21DermisTwo layersPapillary layer (upper dermal region)Projections called dermal papillaeSome contain capillary loopsOthers house pain receptors and touch receptorsReticular layer (deepest skin layer)Contains blood vesselsSweat and oil glandsDeep pressure receptors22Overall dermis structureCollagen and elastic fibers located throughout the dermisCollagen fibers give skin its toughnessElastic fibers give skin elasticityBlood vessels play a role in body temperature regulation2324

Normal Skin Color DeterminantsMelaninYellow, brown or black pigmentsCaroteneOrange-yellow pigment from some vegetablesHemoglobinRed coloring from blood cells in dermal capillariesOxygen content determines the extent of red coloring25Different skin colors26

Skin AppendgesCutaneous glands are all exocrine glands:Sebaceous glandsProduce oil to lubricate skinPrevents brittle hairKills bacteriaMost have ducts that empty into hair follicles; others open directly onto skin surfaceGlands are activated at puberty

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28Appendages of the SkinSweat glandsRelease sweat to surface of skin to regulate body temperatureWidely distributed in skinTwo types:EccrineOpen via duct to pore on skin surfaceApocrineDucts empty into hair follicles29Apocrine Sweat Gland

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31Sweat and Its FunctionCompositionMostly waterSalts and vitamin CSome metabolic wasteFatty acids and proteins (apocrine only)

FunctionHelps dissipate excess heatExcretes waste productsAcidic nature inhibits bacteria growth

Odor is from associated bacteria322006Hoban 33

HYPERHIDROSISexcessive sweatingAppendages of the SkinHairProduced by hair bulbConsists of hard keratinized epithelial cellsMelanocytes provide pigment for hair color34

Hair AnatomyCentral medullaCortex surrounds medullaCuticle on outside of cortexMost heavily keratinized

Trivia: Hair conditioner helps the cuticle lie flat, which makes your hair shiny2006Hoban 35Figure 4.7b

Hair Follicle36

Associated Hair StructuresHair follicleDermal and epidermal sheath surround hair rootArrector pilliSmooth musclePulls hairs upright when cold or frightenedSebaceous glandSweat gland37

Scanning electron micrograph showing a hair shaft emerging from a follicle at the skin surface

38Appendages of the SkinNailsScale-like modifications of the epidermisHeavily keratinizedStratum basale extends beneath the nail bedResponsible for growthLack of pigment makes them colorless39Nail StructuresFree edgeBody is the visible attached portionRoot of nail embedded in skinCuticle is the proximal nail fold that projects onto the nail body2006Hoban 40Figure 4.9

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Skin Homeostatic ImbalancesInfectionsAthletes foot (tinea pedis)Caused by fungal infectionSpread in warm moist areas, such as showers, gyms, poolsBoils and Carbuncles Common in skin areas of sweat, abrasions or at of the nape of the neck Caused by bacterial infectionCarbuncle involves 3+ hair folliclesCold SoresCaused by Herpes Simplex virusSpread by sharing eating utensils/cups, razors, kissing, saliva200643Athletes foot2006Hoban 44

Furuncles (Boils) and Carbuncles

2006Hoban 45Herpes simplex 1- Cold sores2006Hoban 46

Skin Homeostatic ImbalancesInfectionsContact dermatitisCan be caused by an allergic reaction or a skin irritantExample: Poison Ivy, Soaps & DetergentsImpetigoCaused by Staphylococcus or Streptococcus bacteria MRSA can also lead to impetigoSpread by physical contact, sharing clothes, towels, etc.PsoriasisCause is unknown, but develops due to an overactive immune systemFlares are triggered by trauma, infection, stressNOT contagious!!2006Hoban 47Contact DermatitisCaused by allergic reaction or skin irritant48

ImpetigoCaused by one of two bacteria: Staphylococcus aureus or Streptococcus pyogenes.Methicillin-resistant Staphylococcus aureus (MRSA) is also becoming an important cause of impetigo.49

Psoriasis-develops due to an overactive immune system; dead skin cells build up on surface of skin50

51Skin Homeostatic ImbalancesBurnsTissue damage and cell death caused by heat, electricity, UV radiation, or chemicalsAssociated dangers:DehydrationElectrolyte imbalanceCirculatory shock52Rule of NinesMethod to determine the extent of burnsBody is divided into 11 areas for quick estimationEach area represents about 9% of total body surface area53

54Severity of BurnsFirst-degree burnsOnly epidermis is damagedSkin is red and swollenSecond degree burnsEpidermis and upper dermis are damagedSkin is red with blistersThird-degree burnsDestroys entire skin layerAffected area is gray-white or black551st Degree Burns56

2nd & 3rd Degree Burns57

3rd Degree Burn58

Critical BurnsBurns are considered critical if:Over 25% of body has second degree burnsOver 10% of the body has third degree burnsThere are third degree burns of the face, hands, or feet59Skin CancerCancer uncontrolled division of abnormal cellsTwo types: BenignDoes not spread (encapsulated)MalignantMetastasizes (moves) to other parts of the bodySkin cancer is the most common type of cancer!!60Types of Skin CancerBasal Cell CarcinomaMost common typeLeast malignantArises from statum basale61

Skin Cancer TypesSquamous Cell CarcinomaMetastasizes to lymph nodes if not removedEarly removal allows a good chance of cureBelieved to be sun-inducedArises from stratum spinosum62Squamous Cell Carcinoma63

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Skin Cancer TypesMalignant melanomaMost deadly of skin cancersCancer of melanocytesMetastasizes rapidly to lymph and blood vesselsDetection uses ABCD rule65Malignant melanoma66

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69ABCD Rule:A = AsymmetryTwo sides of pigmented mole do not matchB = Border irregularityBorders of mole are not smoothC = ColorDifferent colors in pigmented areaD = DiameterSpot is larger then 6 mm in diameter70Still want to go tanning? (Mom alert! )A study done by the Mayo Clinic, published in 2012, found that over the past 40 years, rates of this potentially deadly skin cancer grew by 800 percent among young women and 400 percent among young men!!The same study found that indoor ultraviolet (UV) tanners are 74 percent more likely to develop melanoma than those who have never tanned indoors; those who tan indoors just four times a year increase their risk of developing melanoma by 11 percent. Indoor tanners are also 2.5 times more likely to develop squamous cell carcinoma and 1.5 times more likely to develop basal cell carcinoma.

71Developmental Aspects of SkinFetal lifeLanugo- downy hair develops at 5th month of gestation; shed by birthVernix caseosa- white, cheesy-looking substance, from sebaceous glands, protects babys skin in amniotic sacMilia- oil buildup in sebaceous glands on babys nose and forehead; generally gone by 3rd week after birth72AdolescenceSkin and hair become oilyAcne- generally subsides in early adulthood

73Senior YearsSubcutaneous tissue decreases, which leads to: Decreased cold toleranceDrier; itchy skinThinner skin; bruising tends to increaseMore sagging due to decreased elasticity74Hair LossBy age 50, loose 1/3 of hair follicles Involutional Alopecia- hair thinningAndrogenic Alopecia:--Male pattern baldness- can in early 20 s, affects crown & frontal scalp--Female pattern baldnesstends to begin in 40 s, affects whole scalpVellus- hair follicles degenerate, hairs are colorless and tinyGraying- result of delayed-action gene-- decreased melanin causes lack of color7576

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