Skin and Body Membranes

Skin and Body Membranes1Types of MembranesMembranes: cover surfaces, line body cavities, and form protective (and lubricating) sheets around organsTwo main types: epithelial and connective

2Types of MembranesEpithelial Membranes: line the cavities and openings that open to the outside of the bodyEx: nasal, oral, digestive, respiratory, reproductive and urinary systemsFunction is to cover and lineInclude the cutaneous membrane (skin), mucous membranes, and serous membranes

3Types of MembranesCutaneous: skinMucous: all mucous producing membranes; adapted for absorption and excretionSerous: line cavities not open to the outside of the body; lung cavities, heart cavity, etc; produce serous fluids for lubrication; names depend on location

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5Types of MembranesConnective Membranes: (synovial membranes) line joints; made of connective tissue only; secrete synovial fluid for lubrication

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7Integumentary SystemThe integumentary system consists of the skin and its accessory organs (hair, nails, and glands)Integument means to cover (Latin)

8The SkinBodys largest organMost important function: PROTECTIONOther functions:Barrier against infection and injuryRegulates body temperatureRemoves wasteBlock ultraviolet radiation from the SunProduce Vitamin DSensory receptorWaterproff barrier9The SkinGateway for sensations of pressure, heat, cold, and pain to be transmitted to the nervous systemTwo main layers: EpidermisDermis10

11EpidermisOuter most layerEpithelial tissue (stratified squamous)Mostly dead cellsUndergo rapid division (mitosis)As new cells are formed, older cells are pushed to the outside and become keratinizedKeratin: tough, fibrous protein; forms hair, nails, and callusesIn other animals forms cow horns, reptile scales, bird feathers, and porcupine quills

12EpidermisKeratin-producing cells (Keratincytes) die and form flexible, waterproof coveringsThickest epidermis is found on palms of hands and soles of feet (big calluses )Outer layer of dead cells shed or washed away every 14-28 daysEpidermis also contains melanocytesMelanocyte: cells that produce melanin: dark brown pigment13EpidermisBoth light and dark skinned people have roughly the same number of melanocytes!The difference is the amount of melanin produced and distributedTwo Factors:HereditySun exposure (tanning)

14EpidermisMelanin is important for protection against UV radiationALL people should limit sun exposure, but especially light skin peopleUV radiation causes DNA damage and can lead to skin cancers such as Melanoma Cancer

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Fig. 6.2a16EpidermisNo blood vessels in epidermis, which is why small scratches dont cause bleedingEpidermis layers: (top to bottom)Stratum corneumkeratinized layerStratum lucidumonly in palms and soles of feet. Stratum granulosumgranular layerStratum spinosumthick layerStratum basalebasal cell layerGerminal cell layergets nourishment from dermal blood vesselsBasement membraneCan Lucy Get Some Bagels17

18DermisInnermost, thick layer of skinMade of living cellsLies under epidermisConnects to epidermis at wavy layer called the dermal papillaeContains blood vessels, nerve endings, glands, sense organs, smooth muscle, and hair follicles

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20DermisHelps control body temperatureOn cold days, blood vessels narrow to conserve heat (pale skin)On hot days, blood vessels widen to warm skin and increase heat loss (pink skin)Tiny muscle fibers attach to hair follicles and contract to pull hair upright when you are cold or afraid (GOOSE BUMPS!)

21DermisContains two major types of glands:Sudoriferous (sweat) glandsSebaceous (oil) glandsBoth pass through epidermis and release products to surface of skin

22GlandsSweat glands (sudoriferous glands): produce watery secretions known as sweat Contain salt, water, nitrogen wastes, lactic acid, etc.Slightly acidic ph: 4-6 (inhibits bacteria growth)Stimulated by nerve impulses that cause production of sweat in response to body temp. changesHelps to cool body2.5 million per personTwo types: eccrine and apocrine

23GlandsEccrine sweat glands: found all over bodyNOT the pores you see on face!Apocrine sweat glands: found in axillary and genital areasLarger, and secrete sweat with fatty acids and proteinsCan be milky or yellowish (pit stains)Secretion is odorless, but source of food for bacteria which grow and produce musty, unpleasant odor

24GlandsSebaceous glands: produce oily secretions known as sebumSpreads across surface to keep keratin-rich layers flexible and waterproofEverywhere but palms and solesControlled by hormonesUsually connected to exocrine glands around hair folliclesCoats surface of hair

25GlandsOil gland contd.Prevents water lossLubricates and softens skin and hairSebum is mildly toxic to some bacteria protectionIf oil glands become clogged with sebum, dead cells, and bacteria: ACNE can result

26HypodermisUnderneath dermisSubcutaneous LayerMostly adipose and loose connective tissue (areolar) that insulates and provides energy reserveNo distinct boundary between dermis and hypodermis

27Hair develops from group of epidermal cells in dermis. Root-portion embedded in skin. Hair and epidermal cells develop from same type of stem cells. Old hair is pushed out by new hair. Hair FolliclesAppendages of the SkinSlide 4.18Copyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsHairProduced by hair bulb (follicle)Consists large columns of DEAD, hard keratinized epithelial cellsMelanocytes provide pigment for hair colorConnected with arrector pili muscleswhy?

Figure 4.7c

29Hair AnatomySlide 4.19Copyright 2003 Pearson Education, Inc. publishing as Benjamin CummingsCentral medulla (inner layer)Cortex surrounds medullaCuticle on outside of cortexMost heavily keratinizedRoot: under skinShaft: outside skinFollicle: pocket in epidermis/dermis

Figure 4.7b30

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32Hair Structure

33Hirsutismcondition of excessive body hair in females or prepubertal males from excessive amounts of androgens (hormones). Androgenic allopecia(male pattern baldness)androgens inhibit hair growth.

Hair DisordersGrow from nail matrix or root (area of rapidly dividing cells)Matrix located near tips of fingers and toesMade of tough, thick layer of keratinNails rest on a bed of tissue filled with blood vessels, giving the nails a pinkish colorGrow at a rate of 0.5 1.2 mm per dayFingernails grow faster than toenails

NailsNails can reflect health problems. Bluish nails = circulatory problem. White nail = anemiaPigmented spot under nail = possible melanoma. Horizontal grooves = malnutrition. Clubbing= heart, lungs, liver problems. Red streaks = rheumatoid arthritis, ulcer, HTN.Spoon nails=iron deficiency anemiaNail DisordersHyperthermiaRise in core body temperature. Can happen when moisture on surface of skin does not evaporate. Higher risk during humid conditions.Can lead to heat exhaustionSx = light headed, dizzy, HA, muscle cramps, fatigue, nausea. HypothermiaCore body temp drops. Progresses from feeling coldshiveringmental confusionlethargyloss of reflexesloss of consciousnessshutting down of organs.

Heat Regulation ProblemsSkin color can also be affected by oxygenated blood. Cyanosisbluish skin color from poorly oxygenated blood. Vasodilationreddish skin color from increase blood supply to skin. Vasoconstrictionpale color from lack of blood to skin. Yellowish colorCan result from increased ingestion of beta carotene. Carotene accumlates in adipose layer beneath skin. If you eat too many carrotsskin turns yellow. Can also be liver problems - jaundice

Skin color via physiologyWrinklesDecrease in vascularity (looks paler)Senile purpurapurple macules formed from blood leaking through fragile capillaries. Dry skinBrown macules (liver spots)Seborrheic keratosispigmented, raised, warty, greasy lesions. Located on trunk, face and hands.

Age-Related ChangesOther Skin DisordersAcne vulgarisAthletes Foot: contagious fungal infectionDermatitis: inflammation of the skinEczema: inflammatory skin disease; dry, itchy, scalyWarts: caused by virusPsoriasis: similar to eczema but more severeRingworm: contagious fungal infectionHives: usually allergic reactionBoils: caused by staphylococcusOther Skin DisordersShingles: viral infection (Herpes Zoster)Herpes Simplex I: fever blistersGenital Herpes: viral, blister in genetal regionScabies: mites burrowing in skin

First degreesuperficial partial thickness burnEpidermis only affectedRx: cold waterHealing within a weekSecond degreedeep partial thickness burnEpidermis and some of the dermisFluid accumulates between dermis and outer layer of epidermis and blisters form. Skin becomes discolored from dark red to waxy white. Healing depends on accessory organs of skinAccessory organs produce epidermal cells that regenerate surface of skin.

BurnsThird-degree----full thickness burnEpidermis, dermis and accessory organs destroyed. Growth can only occur from the margins of the burn inward.May be life threatening Grafting usedAutograftfrom same personHomograftfrom cadaverSkin substitutes used to cover skin while healing.Amniotic membraneArtificial membraneCultured epithelial cells

BurnsEstimating burned area. Rule of 9sAnterior upper extremities = 9%Posterior upper extremities = 9%Anterior trunk = 18%Posterior trunk = 18%Anterior neck and head = 4 %Posterior neck and head = 4 %Anterior lower extremities = 18%Posterior lower extremities = 18%Burns